Forums: Skydiving: Gear and Rigging:
My little project

 


Quagmirian  (A 110392)

Jul 11, 2012, 12:17 PM
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My little project Can't Post

In this thread I'll be posting progress pictures of my (hopefully jumpable) canopy. If I can't get it out of a plane it'll be towed behind a car something. So far I have completed most of the planning and cut out a few parts. I'm going to do a bit of sewing to make sure everything matches up correctly or whether I need to adjust the templates. I'm in two minds about adding a bridle attachment thingy and I welcome technical advice.

Design Information
9 cells
Clark Y(ish) airfoil section
Span: 7.02m (23 feet)
Chord: 2.74m (9 feet)
Area: 210 square feet
Full cell chordwise I-beam style construction, like a Skymaster
Colour: babyshit brown




(This post was edited by Quagmirian on Jul 11, 2012, 12:18 PM)
Attachments: parts2.jpg (172 KB)


Premier Remster  (C License)

Jul 11, 2012, 1:17 PM
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Quote:
If I can't get it out of a plane it'll be towed behind a car something

Car-towing a ramair canopy is a pretty stupid idea. Don't do that.


RiggerLee

Jul 11, 2012, 1:19 PM
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Not sure exactly what you're aiming at here. I will preffes all my comments by saying that unless you're looking for something very specal, a specal aplication there is absolutely no advantage in trying to build your own canopy from scratch. And from what little I see you don't seem to have a good grasp of the back ground nessasary to do it. Not ragging on you just saying.

Now haveing said all of that. I thinkl it's really cool that your strikeing out on a project like this. Way to go. Regardless of all else you will learn a great deal even if your canopy never gets off of your computer. Small minded people here will give you a lot of shit so just ignor them. I will answer your questions to the best of my abillity and help you with what little I know.


First off could you fill us in on your back ground, skill set, and resorces specificly equipment.

second. It sounds very much like you're starting from scratch. Before you try to reinvent the wheel you might start by examining past designs and looking at some of the infomation out there. Bad news is that most of the knowlage is locked away in peoples skulls or in companies but I seemk to recall a few papers and presentations from pia etc. I don't have them in front of me. Hell why don't you take apart an old canopy and try to copy it.

I'll start tossing out some thoughts. Just bits of info that you may or may not be aware of.

If your starting from scratch and you've never done this before start small. How bout you build a kite. say 50 sq ft. It would give you a chance to work out how to main seam, your construction, play with your trim, etc. Start by kiteing the damn thing. Use that to measure your glide angle, lift, give you an idea of how these things change with your break input. Give you some notion of your... I'll call it pitch stiffness. A tendence to stay at one angle of attack and not for instance over fly and role it's nose under. A jumpable model on your first try is probable a bridge too far.

Some other thoughts.
It looks like your panels are rectangular. No panels are not rectangles. In fact a good bit of the secret magic is in the panel shape. At the very least think of it as a shape of rotation. I degress further on this but I'm short of time. where did you get your fabric? Canipy fabric is almost like baseball bat wood. You can't make it out of just any thing. The cloth that you cut it from has to be straight. Take a marker and draw a line across the fabric following one of the ripstop lines. Then lay one long ruler paralel to the warp of the fabric. and use a big frameing square to lay another ruler 90 deg to it. You'll probable find that the shit is crooked. It can bow, it can be at an angle, it can be in an S. Some time you can cutr from the center of the roll. Another trick is to flip the panels so that they form a shevron when you sew them togather. What machines do you have? Any pullers?

Look I could go on and on but I have to go ship some thing.

I think this is cool by the way.

Lee


adamUK  (C 104423)

Jul 11, 2012, 1:29 PM
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I'd build a kite first which would allow you to make mistakes without costing you too much canopy material. Once you've got something that looks about right then do the real deal.

I don't know you'd be able to jump your canopy without dispensation (and you'd have to use a cutaway rig in any case).

But yeah.. gotta admire your aspiration to do this. I am sure you will learn a lot on how they are made, how the deployment sequence works, how they fly and a ton of other stuff in the process even if you don't eventually produce the jumpable product.

Good luck Smile

P.S. realised I'd kinda paraphrased the guy above. ^^^ What he said.


(This post was edited by adamUK on Jul 11, 2012, 1:31 PM)


Quagmirian  (A 110392)

Jul 11, 2012, 1:58 PM
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In reply to:
Not sure exactly what you're aiming at here...
...Lee
Thanks for reminding me of a few things I should have put in my first post. This picture should explain a bit.

I have looked at past designs, that's where I've got most of the information for making this thing. I have also noticed that information is locked away and I have had to second-guess a lot of stuff. That's where I thought this thread might be handy. Copying an old canopy is on my list of things to do, and it's essentially what I'm doing here.

I have built something a bit like this before, and no I didn't jump it, but I did fly it behind a car. I feel like this is a good step forwards.

Yes, the top panels are rectangular. Have I missed something? They certainly look like they should be.

The fabric is where the fun begins. It's some kind of military cargo fabric, definitely not exactachute. I use it because it's very to cheap to practice on. Yes, the cloth is on the cock. The ripstop lines are not at right angles, which is something I've just been ignoring, what a fool I look now. I'll take on board the chevron idea though, thanks.

My machine is a little home thing which struggles to go through lots of material and doesn't have anything useful on it.

Thanks for the enthusiasm by the way. Wink
Attachments: 300652.jpg (88.5 KB)


riggerrob  (D 14840)

Jul 11, 2012, 2:10 PM
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"
In reply to:
... that information is locked away and I have had to second-guess a lot of stuff. That's where I thought this thread might be handy. ...Wink
"

.....................................................................

Try to get your hands on a Parakit/Lone Star manual. Back int h late 1980s, Lone Star sold pre-cut kits to sew your own ram-air canopy. I sewed two of them and put a total of 500 jumps on those two canopies. Both canopies are still air-worthy, but F-111 canopies have fallen out of fashion.
My copy of the Lone Star manual is staring at me from across the room.
Hint: if you are willing to pay the cost of photocopies and mailing, I might share my Lone Star manual with you. Since the company is long out of business, I do not worry about copyright.


RiggerLee

Jul 11, 2012, 3:48 PM
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Honestly at some point you're going to have to learn about real sewing machines. You can get by for now building little kites on your home machine, honestly that's what you should probably be doing right now any way. But eventually yopu're going to need a real machine or a couple. First off where ever you went to buy your home machine don't go there. I don't know what it's like in the uk but here in the us there is like two diffrent worlds. One has the little old ladies that build quilts and clothes to embaris there grand children. And then there is the real world of industreal sewers that use real machines, real fabric and real thread. The two groups do not over lap. At all. If you've been going to a little craft shop, don't go back there, don't talk to them, don't lissen to any thing they say. Pull out the phone book and find a shop that deals with industrial sewing machines. Develop a relation ship with them. You'll know the place when you see it. It will be a wearhouse in an older part of town, there will be no show room. It will just be big shelves with old heads and stacks of tables in the corners and one old guy that knows way way more about what you need then you do. The good news is that what you're looking for is for the most part cheap. Light weight garmit machines are every where and not in great demand. Make sure you get a 110 moter with a good clutch. Start out with just a straight stitch with a reverse, say a consew 230. A needle feed would be nice but you could get by with a drop feed. Next you need a double neadle probable a 1/4 inch gague. It would be nice if it was a reverse. With a binder you dont need that but for this it would be good. Puller. Pullers don't grow on trees. What you need is one like a singer 112-w-116 A bottom puller with a top side roller so you can have a whole pile of shit underneath your arm. You may have to look around to find something like this at a decent price. You need to start thinking about your seam construction and what you will need in terms of folders, tape feet, etc. You're probable going top want to get the folders and plates so that you can swap them out on that one double needle. Odds are they will all be custom. Rarely have I found ane thing off the shelf. You get what you pay for. Expect to send in samples of fabric, seames, tapes, etc. Both sewn and unsewn. figure on several hundred dollars per folder so have this well thought out and don't forget about any tapes that will have to run through the folder. They will need to leave room for them. These are fairly high percision hand made devices with more then a little magic in them. Do not trust any one under 60 years old to build your folder for you. It's a lost art.

Old mill fabric? Look you're going to need 0-3 fabric, eventually you're going to want to use zp. I don't know what you've got but you're not goint to learn much other then how to sew with out tight fabric. You're going to have to learn about supliers. Don't hold your breath on buying any thing, and I mean any thing locally. Do not go bach to the local shop. If it doesn't come on a roll you don't want it.

Air foil. Clark Y? Yah it's been around but it's probably not what your looking for. This aint alumanum. I don't think I'd put a whole lot of brain power into the air foil but I'll toss out some thoughts, keep in mind they are worth exactly as much as your paying for them. First off you're bottom seam is probable going to be flat. It's a compromise on ease of construction. Second you're probable going to want a good bit of camber. third I'd wand the camber and thickness pritty far to the front of the canopy. I think you're looking for a pritty strong moment. I think that would help to keep the front of the canopy from unloading. Beyond that, it's a big fucking sack that only has a passing resimbalance to the rib so don't go over board.

panels. If they're just rectangles then the thing looks like a flat wing. Think about what happens when you bend it. Think about the angle of attack across the wing and how it will bend. The outer ribs will wind up leaned inwards at the ends. Think about the angle of the lines as it opens like a fan. The top skin has to be wider then the bottom skin. No rectangles. Now I'm going to talk a little more out of my ass here. I don't have derrect knowlage of how the diffrent manufactorers make there decisions but I'll toss out some ideas. Lets say you tuuk a line along the glide angle of your canopy. So that is your free stream line. through the end of your riser. Then you have the canopy, center cell loaded rib above that. Then lets say you rotated that airfoil around that line so that you have a positive angle of attack all the way across the canopy reletive to the glide angle/free stream line. So think of it as a surface of rotation. In essence the zero lift line of the canopy would form a cone around the free stream line passing through the riser with a constant angle of attack. The surface is of course more complicated but not by much. Basically intergrate along the surface, just add up the distances along the curve, and at each point look at the distance perpendicular to that line of rotation. That based on the angle for each rib gives you the width of the panel at that point. Very easy for a rectangular canopy. If you get fancier, eliptical, where you basically change the airfoil at each rib you have to get a bit more sneaky. You can form the panel shape by basicly doing an intergration through the law of cosigns to unwrap the panel off of the canopy into a flat plane. In a sence it's basicly a sort of cone. as long as you don't have any sections of... negative gausen curvature it's not a problem. But that's for another day. Set your self up a spread sheet and think about panel shapes. Keep in mind that what I've described here is very... basic. You can actually do a lot between the line trim and panel shape to control the angle of attack across the canopy. This is some of the secret stuff that I can only guess at. And keep in mind that even with this it's still going to be a bit weird when it inflates. Keep in mind that the tail being thiner will "swell" more then the thick part of the canopy. So it will tend to bow the canopy backwards slightly. What I've described is not really adiquite knowlage to build a canopy I'm just giving you an example of how you might start to generate a design or at least where I might start. Take it for what it's worth.

Lee


riggerrob  (D 14840)

Jul 11, 2012, 6:32 PM
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"
In reply to:
... My machine is a little home thing which struggles to go through lots of material and doesn't have anything useful on it. ... Wink
"

...................................................................

Sounds like my second sewing machine: a Pfaff 230. Just a little single-needle that would also do a simple zig-zag stitch. The zig-zag function is handy for sewing bridle attachments, line attachments and suspension line junctions.

I mainly used the straight stitch function to sew both of those kit parachutes.
The key point is that was a 1960s-vintage home machine made of cast iron. Cast iron is the key when sewing through multiple layers of nylon. Cast iron is the only material that will hold the needle in precise alignment with the hook (underneath).

When searching for a parachute-sewing machine, take along samples of the fabric you intend to sew along with a spool of nylon E-thread (military specification and Parachute Industry Association Specification) also known as civilian size 69.

If they try to sell you needles any smaller than 19 gauge, walk away. Most parachute sewing is done with size 21 or 22 needles, ball point or universal point. The key to needles for sewing nylon is ball points that gently push the nylon fibers aside, leaving them structurally intact.

If they try to sell you chisel-point needles (meant for sewing leather) .... they will ruin your nylon fabric.


Quagmirian  (A 110392)

Jul 12, 2012, 12:31 AM
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Thanks for putting the time to give me advice guys, I really appreciate it.


darkwing  (D 4164)

Jul 12, 2012, 2:55 AM
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I built, from scratch, quite a few canopies, starting in the mid 1970's. That seems close to the design time frame you are in. My initial strategy was to copy an existing canopy. It was a 189 square foot foil, a very under appreciated canopy. It flew great. My teammates liked them too. Building a copy gives you a big advantage when you first jump a canopy you built.

Later, after I was confident in my construction methods and skills, I started doing my own designs. There are some minor and major tricks to it, some of which have been mentioned above.

I'll be glad to share with you. PM or email me and we can talk on the phone or Skype.


masterrigger1  (D 14167)

Jul 12, 2012, 3:36 AM
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Quote:
If they try to sell you needles any smaller than 19 gauge, walk away. Most parachute sewing is done with size 21 or 22 needles, ball point or universal point.

Rob,
I agree if you are talking about H/C work, but not if you are speaking of canopy work.

The correct size needle for canopy fabric, if using E thread (size 69), is a 16-18 size needle.


The correct size needle for canopy fabric, if using B thread (Size 46), is a 14-16 size needle.


http://www.thethreadexchange.com/...ry_Code=nylon-thread


MEL


NewGuy2005  (A 50256)

Jul 12, 2012, 10:22 AM
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In reply to:
Quote:
If I can't get it out of a plane it'll be towed behind a car something

Car-towing a ramair canopy is a pretty stupid idea. Don't do that.

No kidding. Never do that. Paragliders do it, but with multiple safeguards and very specific training. I have seen people come close to getting killed, even so.


Quagmirian  (A 110392)

Jul 21, 2012, 12:28 PM
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I took my 7 cell for a spin today and I didn't get killed. I might be able to post some footage of it later.


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RiggerLee

Jul 21, 2012, 1:27 PM
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Out standing!

Did you chop it or land it? How were it's dynamics? It's pitching? What stability checks are you doing? How's the front riser tension? Any points of... mushiness on the front riser stroke?

What kind of rig are you jumping it in? The easiest way to deal with this is to put it in a tersh on a set of mini risers on larg ring harness. With the cutaways on the risers. You can make a container compleatly seperat from the harness so no alteration to the tso'd container. That's how I've always done it. Poor mans tersh rig.

Come on, you got to spill some details. We demand more pictures.

Lee


Quagmirian  (A 110392)

Jul 21, 2012, 2:19 PM
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Woah woah woah, I didn't jump it. It's just got nylon cord for lines at the moment. The airfield owner towed me behind his truck (I know, I know). As far as flight characteristics go, it's pretty shit, and lacks flare power. I took off on the rears and landed on the toggles and it just seems pretty docile. There's only so much I can do with limited knowledge of canopy design and military cargo fabric.


nitrochute  (D License)

Jul 21, 2012, 3:06 PM
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where did you get the warning label?


Quagmirian  (A 110392)

Jul 21, 2012, 3:23 PM
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It is very much a warning label.
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strife

Jul 21, 2012, 3:46 PM
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nice good thinking


adamUK  (C 104423)

Jul 21, 2012, 8:07 PM
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In reply to:
It is very much a warning label.
A very good sense of humour I see.. Tongue


DoZ3r  (D License)

Jul 22, 2012, 9:38 AM
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I love your warning label!


Quagmirian  (A 110392)

Jul 23, 2012, 7:22 AM
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Here are a few pictures from my hemming and I beam work. I found some orange fabric, so that'll be the centre cell.






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riggerrob  (D 14840)

Jul 23, 2012, 9:34 PM
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"
In reply to:
... Yes, the top panels are rectangular. ... Wink
"

....................................................................

Rectangular is fine of bottom skins, but if you use rectangular tip skins, you will end up copying some of Domina Jalbert's earliest prototypes (circa 1970). OTOH if you start tapering top skins, you soon be sewing copies of 1975 vintage canopies.

To quote Dan Poynter's "The Parachute Manual, Volume 2", page 322 - "Crown rigging: Normally all lines at the same chord position (e.g. "A" lines) are of the same length. This anhedral (19-27 degrees, often 21 degrees) "crown rigging" simplifies construction. the slider, risers and harness affect the designed arc. The arc is also temporarily changed by dynamic maneuvers.
Crown rigging dictates that lower cell surfaces should be narrower than than upper surfaces. If the surfaces are cut the same width, the canopy wil open slower and fly slower.
Flat rigging is inherently less stable than crown rigging, yet flat rigging yields a notable glide improvement in steady state, full flight because the lift forces are more vertical. However, flat-rigged canopies do not pen well and do not recover well from dynamic maneuvers.".

IOW "crown rigging" means that loaded ribs continue up along the same angle as suspension lines (when viewed form the front).

Start by guessing the length of harness and risers at 1 yard (er ... one metre for Europeans), then copy "A" line length from a similalrly-sized production canopy.
Then draw a bunch of rectangular bottom skins.
Then calculate cell height at every six inch interval back from the leading edge.
Then calculate the circumference of that (21 degree) arc.
Starting at the tail, draw a top skin the same width (span) as the bottom skin. Then mark it every six inch, moving forward. Calculate widths. Top skins will be trapezoidal (e.g. straight-edged) for more than half the chord, with all the curves in the last third (near the leading edge.

Clark Y is a fine airfoil for parachutes, considering that the Clark Y was invented back (1922) when 98 percent of airplanes had fabric-covered wings.


Quagmirian  (A 110392)

Jul 24, 2012, 9:48 AM
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Thanks for all the information. Please keep it coming. I'm sure you understand that I'm using rectangular top skins and tapered bottom skins to simplify design and construction. Another thing I have to consider is my ribs. For this design, both the non-loaded and loaded ribs use the same template, again, to simplify construction. At my level of competence, I can't see the extra difficulty of designing, fabricating and sewing curved top skins being matched by any appreciable increase in performance. Of course, I understand its significance on higher performance canopies and I might try it on my next build.


RiggerLee

Jul 24, 2012, 1:08 PM
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Depending on the angle of attack of the bottom skin and what line you chose to rotate the airfoil around the bottom skin may or may not be a rectangle. If the airfoil is flat on the bottom side, and a rectangular canopy, then it will be some form of trapizoid. Could be a rectangle but only if that bottom skin is parallel to the line of rotation. The top skin will just be bowed outwards a bit. It's just a bit of work when you make the patern then it's all the same and it will give you a much nicer spread on the top skin of your canopy. How important is it? That depends on your span width and line length. But right now you're bowing something that doesn't want to be bowed. The top skin, angle of the ribs, every thing gets... funky when you try to do that. The earlier comments relate to whether you try to bow the canopy at all. The earliest canopies they actually tryed to make as flat planes by varing the line set spanwise. The probblem is that this actually wants to make the canopy collaps spanwise from side to side. This led to the really low aspect ratio long line set canopies that you see in pictures. By makeing all the lines the same length you direct the lift outwards all along the arc of the canopy. What you're doing right now is trying to take the first canopy and bend it into the other. Not only does this mess with the wing but it also messes with the angle of attack spanwise across the canopy.

This isn't super high speed race car shit that we're laying on you. It's actually pretty basic and comenserit with the level of tecnology that you're playing with right now. Do you have good patern paper? It feels almost like poster board. Are you hot cutting around it? Even with just a paper patern you can get away with that if you have good paper. You may have to buy a pretty big roll to get it. Ask the indutreal sewing guys. I don't recall the proper term they use a lot of shit as well but you might be able to get or order a smaller quantity. It's not hard just knuckle under and do it on your next design.

I'll try to put togather a little spread sheet for you that will help you with your panel shapes. Bit busy right now but I'll see what I can do.

Lee


Quagmirian  (A 110392)

Jul 25, 2012, 3:51 AM
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Right here's the footage.

http://youtu.be/Hfz34gy15tw

From my observations, it's all good, but I think I've shortened the B lines by an inch or two too much. Someone on the ground observed that my right hand stabiliser was flapping like mad, although from watching the video I can now see that it was one of my end cells. Crazy
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RiggerLee

Jul 25, 2012, 8:12 AM
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I'm not sure exactly how you're going about this. Are you a para glider pilot? Ever done any towing? It's actually a bit more complicated then it seems and it can all go fine and you think that every things cool til it's not. You don't hard point some one to the vehical. There's a wench or more like a spool. It's not just that they're trying to feed out more line so that they can get hight it's a safty thing. The canopy wants to fly at a certin glide angle. But it's just as happy 90 deg to the side as it is above. You can get into some thing called "Lock Out" Basicly it happens when you get too far to the side for what ever reason. Cross wind, collapsed cell, inatension doesn't matter. The rope beguins to pull you out from under the canopy and it can excead the athorith of your control input. At that point it bitch slaps you into the ground. Bad scene. The only way to recover is to lower the tension on the rope. Let the pilots body swing back under the canopy so that he can turn in and get more back on to center. That's what the wench, or more accerately the spool with the break is for. The driver can not react fast enough. Don't be stupid. Have you noticed that I am not one of the naysayer that shit's on crazy ideas? When I tell you you shouldn't do some thing... translation: imanent death. Yah you're getting away with it. Only a mater of time. Use a better set up.

Did I miss some thing? It was low res so maybe I'm not seeing it. WHERE'S YOU FUCKING HELMIT? For that mater I'd recamend knee and elbow pads and any other armer you have. Whrist braces is you have some clean enough. Ever seen a lock out? Don't know you but you seem a little too cool to be added to my, rather long, list of friends that have died.

I'm almost done with a spread sheet for you. It seems to be working fine but you and others here will have to go though and play with it looking for bugs. Busy now.

Lee


RiggerLee

Jul 25, 2012, 8:42 AM
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http://www.youtube.com/watch?v=eSxkmDOsdw0

http://www.youtube.com/watch?v=eSxkmDOsdw0

http://www.youtube.com/watch?v=GdE5DyqfUCg&feature=related

http://www.youtube.com/watch?v=zfHF0lRvm0M

This one's a staight up stall
http://www.youtube.com/watch?v=zfHF0lRvm0M

http://www.youtube.com/watch?v=-SzsItkSeRw&feature=related

An example of recovery
http://www.youtube.com/watch?v=NeqcH0YUDIw


Damn it. Couldn't find any really good carnidge videos. I guess people are squemish about publishing fatalities. But you get the idea.

Lee


Quagmirian  (A 110392)

Jul 25, 2012, 10:54 AM
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I value your opinion, but I can't help but be amused by being told by an American to wear a helmet. To address the whole tension issue, I am aware of it, and that's why I looped the tow rope round my chest strap; it'll break easily. I am aware of the inherent dangers of static line towing but it doesn't stop me doing it. Why not try to convince everybody out there who's on too small a canopy that what they're doing is dangerous. How about jumping without AAD's and helmets for that matter?


RiggerLee

Jul 25, 2012, 11:07 AM
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Ok, here's at least some thing you can play with. It's not perfect. In fact it's a little awkward to work with like all my stuff. I'm not a computer guy so there's some anoying little things in it that I don't know how to fix. Like how to make the graphs stay in proportion. But I think it's working right. Play with it and see if you can find any bugs. It should produice rib and panel shapes for retangular and eliptical canopies.

this took me longer then I'd planed but I wanted you to have some functionality. It's got a clark y in it right now but you can put other airfoils in. It lets you mush the airfoil around a bit. Opening up the nose by moveing the leading edge points up and down for top and bottom and forward and back for the bottom. You can change the thickness and the location of the thickness. Between all of that you should be able to smear it around to come close to other airfoils used on canopies. The cord line is the bottom axis along your bottom skin. It's set at 0 AOA right now. That gives you about 6 deg of AoA from your 0 lift line. Play with that you might want a bit more. You can set the estimated glide angle and it will rotate it around the free stream line going through the top of your riser keeping a constant AoA along the canopy span wise. As a place to beguin. Take your best guess. Monkey with it till it looks more or less like an existing canopy. Line the thing and then take it out and peg it down and kite it. play with the trim and get a feel for it's real glide angle, lift curve, and dynamics. Once you think it's workable go back to the computer and work the revised trim and AoA into the model and then start over. At least that's how I would approach it.

This is what it is. Two nights of fucking around. It's straight out of my ass so take it for what it's worth, every penny your paying for it. but it might give you a starting point to beguin playing with. And to all thoes who know better feel free to laugh at it.

I'd strongly advise saveing it as is and then playing with another copy. You can bugger it up easily.

Lee
Attachments: canopyb.xlsx (144 KB)


freekflyguy  (D 11658)

Jul 25, 2012, 3:03 PM
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Hey Phill, where are you jumping now?

I wondered why I hadn't seen you at Tily for ages, I guess the three riggers we have here weren't able to give you enough advice?


sundevil777  (D License)

Jul 25, 2012, 3:20 PM
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In reply to:
To address the whole tension issue, I am aware of it, and that's why I looped the tow rope round my chest strap; it'll break easily.

That's your solution?

Will someone else you know be willing to post on this thread to let us know what happened when you can't?


Premier Remster  (C License)

Jul 25, 2012, 3:34 PM
Post #32 of 243 (4212 views)
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In reply to:
In reply to:
To address the whole tension issue, I am aware of it, and that's why I looped the tow rope round my chest strap; it'll break easily.

That's your solution?

Will someone else you know be willing to post on this thread to let us know what happened when you can't?

Didn't I raise this at the very start of this thread.. Oh, wait, yes I did...


Quagmirian  (A 110392)

Jul 25, 2012, 4:09 PM
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In reply to:
Hey Phill, where are you jumping now?

I wondered why I hadn't seen you at Tily for ages, I guess the three riggers we have here weren't able to give you enough advice?
Alright Buzz! Of course I know I could have asked you stuff, but you know once I start asking questions I don't stop! What does this do? What's the breaking strength of this? What are the advantages of this type of tape over type 3? Why have they used that seam? What's the importance of this angle? How do they do this... There aren't enough hours in the day.


sundevil777  (D License)

Jul 25, 2012, 4:15 PM
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In reply to:
In reply to:
In reply to:
To address the whole tension issue, I am aware of it, and that's why I looped the tow rope round my chest strap; it'll break easily.

That's your solution?

Will someone else you know be willing to post on this thread to let us know what happened when you can't?

Didn't I raise this at the very start of this thread.. Oh, wait, yes I did...

Quite right!

I had heard of how towing can result in being slammed to the ground, and accepted as fact that it was a bad idea, but didn't understand it so well and had never seen it. After reading about it and seeing the youtube videos posted a few posts ago, of course it is easy to conclude that to rely on the chest strap breaking to prevent a lockout is not a good plan.

Anyway, if the OP is going to take such a risk, and it goes bad, having the result posted here might prevent others from a repeat.


Monko760  (B 38424)

Jul 25, 2012, 5:46 PM
Post #35 of 243 (4175 views)
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Success or failure =) Im looking forward to how this thread develops.


riggerrob  (D 14840)

Jul 28, 2012, 11:25 AM
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Hee!
Hee!
You sewed your stabilizers on back-to-front.
Remember that the primary function of modern stabilizers is to hold the slider horizontal, during early stages of opening.
When you sew the deep part of the stabilizer to the front of the canopy, the extra area holds the nose opening closed at low air speeds (see Service Bulletin on Para-Flite Cruisair circa 1981).

Oh!
And take a piece of advice from para-gliders to inflate both end cells before lift off.

Finally, take some advice from some one who has suffered head injuries (concusion, cut forehead, broken nose, etc.) during a crash, and wear a helmet. Brain injuries heal verrrrrrrry slowly.


Quagmirian  (A 110392)

Jul 28, 2012, 12:20 PM
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In reply to:
Hee!
Hee!
You sewed your stabilizers on back-to-front.
Yes I know, I am so stupid for doing that. I actually designed the stabiliser like that on the computer just so I'd know where to put the line attachments, and I can't believe I didn't think it through. Now when the canopy sits in the deployment bag, a bloody great piece of fabric hangs out with the lines. Not good.

In reply to:
Oh!
And take a piece of advice from para-gliders to inflate both end cells before lift off.
It was open before I turned around, it obviously closed again due to my shitty stabilisers.


Blamey  (A 56669)

Jul 28, 2012, 12:44 PM
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In reply to:
Success or failure =) Im looking forward to how this thread develops.

I am on the edge of my seat. This just screams bad idea.


RiggerLee

Jul 28, 2012, 1:46 PM
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What do you mean? Bad idea? How do you think every body else got started? Ya think PD just sprouted out of the ground fully formed. No Thouse guys started out sewing building canopies in their spare bed room.

The guy is curious. He wants to learn. Not saying he wont die during the learning curve, especaly if he keeps up doing silly shit, but he's allready learned more about canopy flight, construction, and design then most will ever know. And if he's half way smart about how he goes about this there is no reason why he should have any problems.

I'm proud to chear him on. I wasn't much better off whet I built my first base rig. Now I'm building supersonic drogues for sub orbital recovery systems.

Lee


sundevil777  (D License)

Jul 28, 2012, 6:17 PM
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In reply to:
What do you mean? Bad idea?

Being towed up, thinking that the chest strap will break if he gets into a lock up situation. It seems like it would be much safer to launch from a slope, but of course not so convenient if a suitable hill is not available.


Quagmirian  (A 110392)

Jul 28, 2012, 6:31 PM
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Drew up a new stabiliser for this build which keeps all the slider stops the same linear distance from the risers, I hope that'll keep the slider in the right position.
Attachments: 9cell_lines_stab_new.png (34.4 KB)


RiggerLee

Jul 28, 2012, 8:30 PM
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Air foil looks reasonable if a little thick. What's the thickness ratio? Has the panel spreadsheet worked for you? I think you could reduice the lengths of your cascades, ie I think the point could be higher. Just for convenence of construction I'd make the B and D lines the same length. Now haveing said all that I'd lose the cascades entirely for now. It's easier to monkey with the trim with out them. And you don't even have to sew the tops. Just do like a sheet shank and the fingure trap it.


Lee


riggerrob  (D 14840)

Jul 29, 2012, 3:27 AM
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Yeah!
Whatever Riggerlee said, plus you might want to extend the stabilizers all the way to the trailing edge. Longer stabilizers will help (structurally) stabilize the rear corners (ala. Triathlon and Diablo).


Quagmirian  (A 110392)

Jul 29, 2012, 6:27 AM
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@RiggerLee That's not actually the precise airfoil I'm using, it's just representing the direction of the wing, in case you thought I was putting the lines and stabilisers on backwards. Wink The airfoil I'm using has a thickness of 15%. I'm not using the spreadsheet you gave me on this build, but I am keeping it for next time, definitely. I'll be using nylon cord tied with knots for the lines, initially, like on my white 7 cell. That will allow me to play with the trims before I commit to cutting and sewing a line set.

@RiggerRob I wanted a bit of stability in brakes, and I thought that chopping the stabiliser back halfway to the D line would do that, silly me.


Blamey  (A 56669)

Jul 29, 2012, 9:20 AM
Post #45 of 243 (3931 views)
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In reply to:
In reply to:
What do you mean? Bad idea?

Being towed up, thinking that the chest strap will break if he gets into a lock up situation. It seems like it would be much safer to launch from a slope, but of course not so convenient if a suitable hill is not available.

Exactly this. It's not the building of the canopy that that worries me, I too am fairly impressed by the progress he has made. but the testing methods. Doing things that are known to be unsafe and not taking enough time to make sure you are being as safe as possible.


Quagmirian  (A 110392)

Jul 29, 2012, 9:56 AM
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If it makes everybody on this site feel better, I said I would never be towed at the airfield again. There are some hills near where I live, though.


mark  (D 6108)

Jul 29, 2012, 10:35 AM
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In reply to:
If it makes everybody on this site feel better, I said I would never be towed at the airfield again. There are some hills near where I live, though.

I see you have left yourself the option to be towed somewhere else, and you didn't say you would be using those hills near where you live.

Mark


AND1  (C License)

Jul 29, 2012, 12:42 PM
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Phil do yourself a big favorer and stop your silly antics you have already been BANNED from one dz that i jump at because you was a danger to yourself and you can not call it a canopy its a very big kite and what happened to the orange kite you built nobody in there right mind will ever let you jump out of a plane with it and even a rigger tried giving you advise which you went mad at them because they was not telling you what you wanted to here,please stop before you really hurt yourself or others around you and from what i remember of you you dont no how to say no, its not you and if you carry on doing this project which you will you are going to hurt yourself really bad or others around you and for god sake WEAR A BLOODY LID and phil im not having a moan or a dig I'm only looking out for your safety and your life and fair play you have built somthing not many others will ever have a clue to do including myself


riggerrob  (D 14840)

Jul 29, 2012, 1:14 PM
Post #49 of 243 (3883 views)
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"
In reply to:
... @RiggerRob I wanted a bit of stability in brakes, and I thought that chopping the stabiliser back halfway to the D line would do that, silly me.
"

.................................................................

Stability in deep brakes is a complex subject. Hard-core accuracy competitors depend upon vented stabilizers, flares, keels, etc. to channel airflow in a predictable direction when the stalled airflow is trying to wander about at random.
To better understand stability in deep brakes, inspect an Eiff "Classic," NAA Jalbert "Para-Foil" of Performance Designs "Zero" canopy.


riggerrob  (D 14840)

Jul 29, 2012, 1:14 PM
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"
In reply to:
... @RiggerRob I wanted a bit of stability in brakes, and I thought that chopping the stabiliser back halfway to the D line would do that, silly me.
"

......................................................................

Stability in deep brakes is a complex subject invovling vented stabilizers, etc.
Hitn: look over an Eiff Classic, Jalbert "Para-Foil" or Performance Designs "Zero" to get a feel for how sophisticated their stabilizers are.


Quagmirian  (A 110392)

Jul 29, 2012, 4:59 PM
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In reply to:
Phil, do yourself a big favour and stop your silly antics you have already been BANNED from one dz that I jump at because you were a danger to yourself. You cannot call it a canopy, it's a very big kite and what happened to the orange kite you built nobody in there right mind will ever let you jump out of a plane with it and even a rigger tried giving you advise which you went mad at them because they was not telling you what you wanted to hear,please stop before you really hurt yourself or others around you and from what i remember of you you dont no how to say no, its not you and if you carry on doing this project which you will you are going to hurt yourself really bad or others around you and for god sake WEAR A BLOODY LID and phil im not having a moan or a dig I'm only looking out for your safety and your life and fair play you have built somthing not many others will ever have a clue to do including myself
I don't remember meeting you Andy, which DZ have I been banned from?


Quagmirian  (A 110392)

Jul 31, 2012, 12:18 PM
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Here's a question for all you knowledgeable people out there. Is a single row of zigzag stitching an acceptable way to secure a fingertrap on a suspension line? I could swear I've seen it on some older flight concepts designs. I would take a picture of what it looks like, but my camera can't focus on it.


indyz  (D 28525)

Jul 31, 2012, 12:48 PM
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I've seen older canopies use a few inches of loose zigzag with a couple of stitches worth of over-stitch at each end.

My favorite way to sew lines without a bartacker, though, is a technique that I think hookitt posted a few year back. Sew a pass of zigzag, then pick the foot up and move the line back to the starting point and sew a second pass right over the top. The loose thread should be trapped in the second pass. It works well in a lot of places that you would normally use a bartack. For line work, make sure that the stitch is narrow enough and centered so that it goes through both lines in the fingertrap. If it's a line on a canopy I set the width and SPI to match the factory bartacks. 3/4" long and 42 total stitches is a good starting point if you don't have anything to compare to.


RiggerLee

Jul 31, 2012, 1:57 PM
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I think the sewing is over rated in it's importance. Remember that as long as you have a decent length finger trap most of the strength is in the finger trap it self. Length varies by line and weave but 4 inches is a good round number. The stitching is more then any thing else to prevent it's slipping before it has good load on it. The truth is a little more complicated. Some joints are more problimatic then others. As an example a casscade really likes to have a little tension on the A line to help with the strength of the B line junction. So we sew things. Don't over think it. You could almost get by jumping the canopy with out sewing any thing. The line attachments that I described earlier as an example and you'll want to to play with trim so make those finger traps long or leave tailes hanging out. Long finger traps shrink line. Some times just finger trapping a section of line in to a suspension line is an easy way to treak the trim on a canopy.

As to sewing. We've done every thing over the years and it's all worked. With just a little home machine and a test bed canopy I'd just do a relitively lose zigzag say an inch and a half to two inches long. Make it lose enough that you will be able to take it out if you have to. Glide path did some thing like this for years on dacron line. Remember, Test bed.

Best way to sew it is to make a "Line Jig" Take two peaces of webbing, weight depends on line say type eight for 825 spectra, About 5 inch long. Spread them to the width of the finger trapped line. Put two peaces of type four tape across the ends. sew them across the ends to keep the spaceing. You have a window. Place the line on the machine. Place the jig on the machine on top of it webbing down so it stadels the line. It will hold the line centered as you sew it and lit you feed it much more smoothly. The jig and line all feed through the machine as one. Slide the line out , put a new one in and repeat. Once you've done that set. I like to chain link the lines leaving a gap and then starting again below the cascade so that all the sew points are there togather. Move on to the next group. You can count and inspect them all togather right there. Remember, if you do a non cascaded line set for now you can do all the lines sepperatly and then larks head or sheet shank the lines onto the canopy rather then sew them with the whole pile of canopy in your lap. Your going to be fuicking with this so you don't need a lot of complexity slowing down the evelutionary process. And when you're pre planning you're trim changes that you're going to make in the field when testing. Remember It's easier to make lines shorter then longer. Pre mark all your trim changes with diffrent color sharpies. Buy a box with a whole rainbow.

Basically I'm saying that I'd build my self a set of non cascaded "test lines" pre marked at various trims. Left unsewed at eather the top or bottom. Mark them with various colors of sharpies and just chang them with a little wire fid. I'd take this out and tye it down at the risers or a little longer. One straight peace of webbing or line at the base will let you make a dirrect measurement of glide angle. I'd measure glide and play with stability at a viriety of trims and then go back and feed that back into my model. So at that point doing the math you've got a spread of glide angles at various AoA for the canopy. As go back to computer you can incororate that into you're next plane form to optimise you're next panel set. Then the cycle repeats till you've got some thing that a nice smooth wing with good lift across the canopy, about the right trim you want, and some idea of it's stability. Play with you're break as well. For each of those trims measure three or four break setting down to half breaks. As you play more with it out of the airplane You'll be able to start equateing that data to how it pitches and setts up. Withen two possable three generations you should have something that you're willing to at least test jump if not yet ready to land. Don't go and do some thing silly like comit your self to landing a new canopy till you think you're happy with how it pitches and it's stability.

Lee


nitrochute  (D License)

Jul 31, 2012, 3:49 PM
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the late Freeman Frame from FWF Industries( they used to make the original braided dacron line for para flite) always said the rule of thumb was 20 times the diameter for trapping. the ONLY thing stitching does is keep the trapped portion of line from creeping back out when there is no load.the stitching does not add any structural strength.


theonlyski  (D License)

Jul 31, 2012, 4:27 PM
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In reply to:
the late Freeman Frame from FWF Industries( they used to make the original braided dacron line for para flite) always said the rule of thumb was 20 times the diameter for trapping. the ONLY thing stitching does is keep the trapped portion of line from creeping back out when there is no load.the stitching does not add any structural strength.

A guy I worked with quite possibly inspired the testing to find that 'rule of thumb'. For most lines it's fine, but there are some out there that will slide right out with that short of a finger trap. Mostly a non-issue on the sport side of things (with the lines we use) but it CAN vary.


masterrigger1  (D 14167)

Aug 1, 2012, 4:44 AM
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<shakes head at some of the utter bull crap posted in this thread>

Lee,
You gave the OP a flaming because he did not wear a helmet and then you turn around and give out bullshit info!

WTF!!!

Quote:
You could almost get by jumping the canopy with out sewing any thing.

This is a good example.

We do not need someone out there to read this and actually go try it because the finger trap can work loose during packing and deployment if not sewn.





In reply to:
Best way to sew it is to make a "Line Jig" Take two peaces of webbing, weight depends on line say type eight for 825 spectra,
Quote:

825 Spectra only exsists in PD's world. It is a number they used to identify coated 725 line verus the un-coated 725 line.

In other words, there is no such animal.....
Just look at the identification label on the spool.
Glide path did some thing like this for years on dacron line.
Quote:
They did it on Spectra also.
Flight Concepts ( New Name) still uses that method.
It is done with a bartack machine BTW....
Basically I'm saying that I'd build my self a set of non cascaded "test lines" pre marked at various trims. Left unsewed at eather the top or bottom. ....
Quote:

This is the final clue that you do not have one!

There are major differences in a casscaded line set and a non-casscaded one.

Casscaded line set uses line length AND the intersects of the B and D lines to set up the CG of the canopy.
Non-casscaded line sets use just total line length to achieve the same.
Therefore, the dimensions should be different for each.


Playing with this stuff is dangerous and should be treated as such.

The last thing we need is someone to go in because of mis-information and there is a ton of it in this thread.


MEL


Quagmirian  (A 110392)

Aug 1, 2012, 8:54 AM
Post #58 of 243 (4144 views)
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That's why I posted a while back about line trims on the Optimum reserve. I ended up ringing PD, and the reason they don't give out line cascade points is to stop people like me from manufacturing duplicate line sets. Line trim charts are to check your canopy is in trim only. The way I have created my line lengths is to copy the total lengths from a known canopy, and then put cascades halfway up the longer line. I then cut these out of cheap, strong, nylon cord and tie them in knots as a temporary line set.


RiggerLee

Aug 1, 2012, 11:35 AM
Post #59 of 243 (4113 views)
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Mother fucker. This stupid computer just erased my entire long ramoaling post.

Man, I don't feel like typeing all that again. I'll be brief.

Sewing finger traps at line attachments. I told the whole story before but I don't have the patintce to re type it. I'll just say that I've got hundreds of jumps on canopies like this as we test jumped them. It works fine. If you are refering to cascades, yes you note that I mentioned that they were dependent on the main line tension to hold them.

825, Yes that's correct. I do tend to use the terms interchangable depending on who I'm talking to. PD has almost become a standard in the industry to the point that there nominclature has become almost a standard. It's the easyest way to comunicate some times. I also ask for a klenex when I need to blow my nose not a faceal tissue. Sue me. I don't think this guy has descovered CSR yet. If he had I'd have called it 9512-725. You know what that means but he wont.

Red has a very nice bartacker... now. That wasn't allways the case. Or at least furries old one must have been defective because it changed length randomly from line to line on a line set. In fact I beleve I remember when they baught it. I remember they were kind of excited. We all have nice toys now, the industry has come a long way. but asking the boy to buy a $5000 pattern tacker is probable a bit much. I stand by the process I described. If the boy wont's to sew line sets on his mothers home maching that's his best bet.

Cascades. I'm very aware of the diffrences between a cascaded and and uncascaded line set. Based on your commit I think I have a better grasp of the math then you. That is in fact why I recomended that he beguin by playing with a non cascaded line set. It's actually much simpiler.

What you are trying to say is... half right. It's not about the CG of the canopy. What it's actually about is the pressure distrobution across the airfoil. If you look at the coeficent of pressure across the airfoil you can basicly look at the lift distrobution along the cord line. This can be set of in a statics model if you were so inclined but mostly people do it by rule of thumb. The bitch of it is that the Cp changes across the airfoil as you change angle of attack. This can change the load on the cascade and bend and destort the airfoil. Cascades are actually a bad thing. We really shouldn't have them in our canopies but it's a compermise betweed drag and a lot of spigetti and the stability of the wing. That's what we're really talking about. As you go from a non cascaded line set to one with cascades yes, the lengths do change. As an example when you cascade a line set the B line is almost the same but the A actually gets a bit longer. The B actually has a bit more load on it in flight and pulls the cascade to the rear. The down side of this is that when the canopy comes to a higher angle of attack, eg. durring flare, the pressure distrobution changes and the load on the A line increases and it actually tips the nose up by distorting the airfoil as the cascade shifts. The CG does not chang relitive to the 1/4 cord point of the canopy the airfoil just bends in a bit of a z. It's suttle but there. It's enough that you can actually improve the performance of a canopy at higher angles of attack by removing the cascades on the A/B lines. Yes, this means tweeking the trim in the revers of what I described before. A lines get shorter. But some times it can be worth it to do this at least on say the center part of the canopy. Again it's a compromise.

Is that a bit clearer? Would you like me to send you a presure diagram? I was trying to avoid confusing the poor guy. So Like I said. Maybe he should just start out with a nice non cascaded line set. Nice and simple. Easy to adjust. Easy to play with.

If I've been unclear I'l be happy to explane further. If you want a debate of design I'm down for it. But if you want to get it on you better bring the math cause I was busting the curve in partial courses as a freshman. By the end of the semester it was down to to the grad students and me, and I think one senior was still hanging in there. Can't spell for shit but I could always do the math.

Lee


masterrigger1  (D 14167)

Aug 1, 2012, 12:56 PM
Post #60 of 243 (4092 views)
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Quote:
Sewing finger traps at line attachments. I told the whole story before but I don't have the patintce to re type it. I'll just say that I've got hundreds of jumps on canopies like this as we test jumped them. It works fine. If you are refering to cascades, yes you note that I mentioned that they were dependent on the main line tension to hold them.

My whole point is that you do not give out bad advice regarding not sewing fingertraps..period.

It is straight up,bad advice and dangerous.

If someone is too lazy to spend 20-30 seconds to rip out a simple bartack or other sewn method, then he/or she needs to do something else in this world IMHO!

Quote:
825, Yes that's correct. I do tend to use the terms interchangable depending on who I'm talking to. PD has almost become a standard in the industry to the point that there nominclature has become almost a standard.

They are not the majority.
The other few dozen manufacturers and the hundreds of riggers out in the field are the majority.
Most tend to use the tensile strength name that the braiders use.
This eliminates confusion amongst the majority BTW.


Quote:
Red has a very nice bartacker... now. That wasn't allways the case. Or at least furries old one must have been defective because it changed length randomly from line to line on a line set. In fact I beleve I remember when they baught it. I remember they were kind of excited. We all have nice toys now, the industry has come a long way. but asking the boy to buy a $5000 pattern tacker is probable a bit much. I stand by the process I described. If the boy wont's to sew line sets on his mothers home maching that's his best bet.

Actually in earlier years, they just used a Singer 20U....

Then progressed to bartackers, and finally to programable bartackers.
Cascades. I'm very aware of the diffrences between a cascaded and and uncascaded line set. Based on your commit I think I have a better grasp of the math then you. That is in fact why I recomended that he beguin by playing with a non cascaded line set. It's actually much simpiler.

Quote:


Why would you venture to think that you have a better grasp on this?

I have built literally thousands of line sets over the years and also for virtually every canopy out there in use today.

What's your resume or experience in line manufacturing and canopy design?

I also doubt very seriously that you have a higher concept of math, but it could be possible.

And remember, I have Excel and CAD programs here too!
What you are trying to say is... half right. It's not about the CG of the canopy. What it's actually about is the pressure distrobution across the airfoil. If you look at the coeficent of pressure across the airfoil you can basicly look at the lift distrobution along the cord line. This can be set of in a statics model if you were so inclined but mostly people do it by rule of thumb. The bitch of it is that the Cp changes across the airfoil as you change angle of attack. This can change the load on the cascade and bend and destort the airfoil. Cascades are actually a bad thing. We really shouldn't have them in our canopies but it's a compermise betweed drag and a lot of spigetti and the stability of the wing. That's what we're really talking about. As you go from a non cascaded line set to one with cascades yes, the lengths do change. As an example when you cascade a line set the B line is almost the same but the A actually gets a bit longer. The B actually has a bit more load on it in flight and pulls the cascade to the rear. The down side of this is that when the canopy comes to a higher angle of attack, eg. durring flare, the pressure distrobution changes and the load on the A line increases and it actually tips the nose up by distorting the airfoil as the cascade shifts. The CG does not chang relitive to the 1/4 cord point of the canopy the airfoil just bends in a bit of a z. It's suttle but there. It's enough that you can actually improve the performance of a canopy at higher angles of attack by removing the cascades on the A/B lines. Yes, this means tweeking the trim in the revers of what I described before. A lines get shorter. But some times it can be worth it to do this at least on say the center part of the canopy. Again it's a compromise.
Quote:

No, it was all right!

The CG can be altered by the line dimensions (casscaded or non-casscaded). That is fact.

Yes, changing the CG changes the pressurization of the canopy, so it still boils down to where that weight is hanging under the wing...
Is that a bit clearer? Would you like me to send you a presure diagram? I was trying to avoid confusing the poor guy. So Like I said. Maybe he should just start out with a nice non cascaded line set. Nice and simple. Easy to adjust. Easy to play with.
Quote:

Lee,
I am already ahead of you in that game. Like I said, I have been dealing with lines, canopy trim and trim specs for years.
I think I am past a primer in canopy design.

I also think the OP is past that as he is already flying his canopy.

If I've been unclear I'l be happy to explane further. If you want a debate of design I'm down for it. But if you want to get it on you better bring the math cause I was busting the curve in partial courses as a freshman. By the end of the semester it was down to to the grad students and me, and I think one senior was still hanging in there. Can't spell for shit but I could always do the math.


... I too excelled in math at a very early age.
...and also, actually went to school believe it or not!


I think you are tooting your own horn just a little too much IMHO!


MEL


RiggerLee

Aug 1, 2012, 2:21 PM
Post #61 of 243 (4081 views)
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The CG is going to hang underneath the canopy at a point dependent on it's AC and moment. Glide and AoA chase each other to stabillity. Yes we control where that settles through the line set. None of that is under debate. Maybe my first attempt at the post would have been clearer but the machine ate it.

The question was how cascades effect the canopy. And that is not through a grose change in the CG but through the abbility of the cascade to float forwards or back dependent on it's loading. That is where the trim change, change in the line set, it's really to maintain the same trim, comes from between the two types of line sets. Unforenently it can only be optimised for one mode of flight and will lead to distortion in others. As to how big a problem this is depends on the angle of the cascade and how critical the wing is. He has mentioned stabillity in deep breaks and it is noticable even in conservitive canopies on deep break approaches. In fact it was one of the things people would tweek on older acceracy canopies.

This has degenerated into a little bit of a debate between us. Part of it I think is symantics. Writeing is not my best means of comunication and I'm not sure you're always understanding me. This is to some degree my failing.

I think that although the things you say are not wholley wrong I beleave you are missing some of the suttaller issues as to how and why these things work. This is a good example. You're statement that the trim changes between a cascaded and non cascaded line set is corect but I take issue whith your statement as to why this is.

I'm not trying to give you lessens although I will debate points with you. I was a little verbose not so much because I felt that it was nessasary for you but in hopes that the guy in question would more clearly follow what we were arguing over.

But right now I need to get back to sewing. I'm behind.

Lee


Quagmirian  (A 110392)

Aug 1, 2012, 7:35 PM
Post #62 of 243 (4054 views)
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I've been practicing a little bit on my finger traps.
Attachments: fingertrap_maillon.jpg (218 KB)


RiggerLee

Aug 1, 2012, 9:08 PM
Post #63 of 243 (4040 views)
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Loops a little long. Other then that they look fine.

As to how long the loop... good question. I think there are a couple of issues. One argument says that the lines should not be able to slip over each other. If it sets on top of another line the bump of the lower line can be a sharp enough radious to cut the lin on top of it under load. Note that this is some thing you see in really heavy test drops, cargo weights. On the other hand if the loop is to tight around the shaft of the link it can pull apart hard enough at the Y to tear the mouth of the opening causing the line to fail at the junction rather then at the end of the finger trap which is the normal failure point. I've seen that too when you start to get above about 1,500 lb. I've also hear it said that the loop should not allow the line to slip over the barrel of the rapid link assuming you are useing one and size it based on that. You'll probable wind up with a 1/2 to 3/4 inch loop depending on line and link. and of course cut the line off at as shalow of an angle as the weave will permit. Heavier lines you actually cut yarns at intervals along the line to smothly form a taper. Like the heavier line/"rope" of a sail boat. You can actually do this with braided core line by finger traping the core and the sheath into each other and the that junction actoally winds up inside the line above the loop. That's cool but I don't think I can explane it over e-mail. I only learned to do that a few years ago when I started sailing. I'd always wondered how they did that. I was jumping up and down with excitement when I finally learned how it worked. Other then that it looks fine. Sewing looks good. Don't feel you have to sew right up to the junction.

Is that you're nylon line? How's it's stabillity? Streachy?

Lee


Quagmirian  (A 110392)

Aug 1, 2012, 9:53 PM
Post #64 of 243 (4035 views)
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It's some cuttings of 400lb dacron I'll hopefully be using for my canopy.


Quagmirian  (A 110392)

Aug 14, 2012, 3:01 AM
Post #65 of 243 (3913 views)
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I took on a bit of Riggerlee's advice and thought about the shape of the inflated canopy. What I have done for my kites in the past is a rectangle for the bottom skin, and a rectangle for the top skin. This works well enough, but it is not the ideal solution. I didn't really understand what RiggerLee was on about, and I couldn't use the excel tables because I'm using a proprietary airfoil, so I came up with my own. Basically, the bottom skin is still rectangular, but the top skin has additional width which is proportional to its height obove the bottom skin. This meant I had the take my smooth rib design and make it into a series of points. The good news is that should make matching up the parts for sewing later easier.

I'm thinking about fabricating a 110 sqft model to see how well this works.
Attachments: pattern.gif (10.0 KB)


RiggerLee

Aug 14, 2012, 6:06 AM
Post #66 of 243 (3888 views)
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That's pritty much it. It look just about right. The question of whether the bottom skin is rectangular or not is a question of what line in space you rotate the rib around to create the pannel. In this case and in the example I sent you that line happened to be paralel to the bottom skin of the canopy. That does not nessasarily have to be the case. If you rotate the airfoil you can rotate it around to create a constant angle of attack around the line of rotation. Damn I'm not saying that very well. As you have it there if the canopy flies along the direction of the line you are rotating the canopy around it will be at "zero" angle of attack all across the span. Not to say that it's not makeing lift, keep in mind where your zero lift line, seperit angle, is. So if you want it to fly at a greater or lesser angle then the bottom skin will not nessasarily be a rectangle. I am so not explaining this well. Dork around with it a bit changing the angle of attack. It's ment to rotate the airfoil around a stream line to create the panel shapes. Now what it doesn't do is to tell you any thing about it's performance at that angle of attack and where it will want to fly. The line lengths it gives out are just an after thought based purely on an "assumed glide angle that you enter. It's ment as nothing but a starting point. From which to do a first cut. Once you play with a number of trims and phisically measure the glide that it wants to fly at and from there the AoA of the airfoil you can then feed those numbers back into the program to improve you're panel shape for where you are really flying.

Does that make any sence at all? In any case what you have there is exactly what you have created. If you feed your corordonents into the basic airfoil shape at the very begining it should proliferate through out the document. It will actually let you smush the airfoil around moveing the leading edge points for the top and bottom skin to change the nose cut. You can move the thirty percent point on the airfoil forwards and back to control the location of the greatest thickness/camber of the airfoil. and you can change the total thickness. The other nice thing is it will do patern shapes for an eliptic canopy. I just put in a simple rule to allow you to easily change the taper but you could easily set the rib lengths manualy to what ever you want. It rotates the 25% cord point so there will be more taper on the trailing edge then the leading. It basically unrolls the panel off of the wing as a section of cone. It's broken into a bunch of triangler panels to spread it out flat into the pattern it gives you. All in all it's a good bit for a couple of nights fucking off.

I'd almost have to walk you through it. You might have to give me a call. I don't supose you have skype on your computer?

Lee


riggerrob  (D 14840)

Aug 14, 2012, 7:58 AM
Post #67 of 243 (3867 views)
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Nice finger-traps!

Like the other poster said, you might want to make them a bit smaller. How much smaller is a question of whether to make them slightly bigger than the threads on Maillon Rapide links (redundant, I know), or slightly bigger than the hexagonal barrel.
The goal is to make the loops just big enough that you can slide them onto links without scratching them across threads.
For quality control, find a pencil, or pen of rod that is slightly bigger than your threads. Pull the loops tight around your rod and sew. Then you will have consistent loop sizes.

While we are on the subject of quality control ... try making your bar-tacks slightly narrower, so that all the stitches catch the inner line.


ChrisD  (No License)

Nov 11, 2012, 4:16 PM
Post #68 of 243 (3693 views)
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Wink

That is an awsome warning label!!


Clouddancer22  (D 11672)

Nov 19, 2012, 6:00 PM
Post #69 of 243 (3487 views)
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Wonder how it came out and why we haven't heard anymore????


potatoman  (Student)

Nov 19, 2012, 10:33 PM
Post #70 of 243 (3429 views)
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didn't read the full post, I am not a rigger either.

As for getting pulled up into the air, check out hangliding scooter tow launches on the web.

Basically they mount the scooter, and put line on the back wheel drum. I have seen one do about 1mile of rope/line out, giving at least 800-1000ft climb on the hg.

Be carefull though.


Quagmirian  (A 110392)

Nov 20, 2012, 6:38 AM
Post #71 of 243 (3330 views)
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In reply to:
Wonder how it came out and why we haven't heard anymore????

HAW HAW HAW IT'S FUNNY COS I'M DEAD LOL.


Clouddancer22  (D 11672)

Nov 25, 2012, 7:30 PM
Post #72 of 243 (3090 views)
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Hunh? I was enjoying your thread. I've participated in several tso projects and military trials . . . Don't be wierd on me now! Smile


Quagmirian  (A 110392)

Nov 25, 2012, 8:04 PM
Post #73 of 243 (3082 views)
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Oh, ok. As of right now I am looking for some decent pattern paper so I can cut out my parts and make a model. I'm also trying to find out more about slider stops.


RiggerLee

Nov 25, 2012, 8:39 PM
Post #74 of 243 (3069 views)
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I actually had to go to a paper manufactorer. There was one there in Dallas. I went in and explaned what I wanted. I had to finger fuck a few samples but they had exactly what I needed right there in the ware house. It wasn't even that exspencive. honestly the hardest part of the whole thing was putting the roll in the car. It out wieghed me by a good margin. Paper is HEAVY. But I've got a life time supply of patern paper.

You're looking for some thing about the weight of poster board. Mine is manilla in color. Sorry Wish I could tell you more but that was years ago. Tryed to get what I wanted else where in smaller quantities but no joy. Poor me I had to buy a whole roll for half the total cost of buying a smaller quantity.

As for the stops, Get some large finder washers. There's actually a good bit of force on them. Don't skimp perticuarly on how you sew them to the lines. The stabalizers tend to get tears around the stops. Or at least that's where they start. I'm not sure it's extreame stress so much as the fact that the fabric is always at a weird bias there. You get weird little tears. So don't be afraid to put some tape there running along diffrent angles to help protect it from weird loads. See how PD runs a tape across the top of the stops or a vertical tape.

Lee


Quagmirian  (A 110392)

Dec 4, 2012, 1:04 AM
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I had a very productive conversation with J Wragg; he answered a lot of my questions and make me think about a few things that hadn't crossed my mind. I may have hit a snag as far as testing goes, see the BPA ops manual:

"Parachutes may only be used if they are manufactured for Sport Parachutists or Military Parachutists, by recognised parachute equipment manufacturers or riggers with the necessary qualifications."

However:

"BPA A Licence parachutists and above may perform cutaways (at a club PLA/DZ) with a cutaway `rig designed for the purpose, provided they have CCI permission and have been thoroughly drilled in the cutaway procedures."


So technically I could do a cutaway jump on my A licence, but I'd have to leave the test jumping for someone else for now.


mr2mk1g  (C 103449)

Dec 4, 2012, 5:14 AM
Post #76 of 243 (3994 views)
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You could apply for a waiver from STC, esp if your CCI/DZO/rigger were behind you. Not sure of your chances of it being granted mind.


RiggerLee

Dec 4, 2012, 11:01 AM
Post #77 of 243 (3941 views)
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For now you can learn a great deal about it's stability and dynamic caricteristics by playing with it up high and then chopping it. If you hook a small weight to one of the toggles, little sand bag, just before you cut away it will streamer straight down very nicely. That's really where you should beguin with this in any case. You really don't want to feel comited to landing some thing that you know little about only to find that it has stabillity problems or does not pitch well dynamicly.

You might look around for a master rigger that would be interested in your project and enjoy working with you on it. Even just an endorsment or sign off on aplications would go a long way towards makeing you look legitament. There has to be a process here. Where do new manufactorers come from any way? And I think you'll find that a lot of the older... board members, or what ever, that you're dealing with may remember the days when the "manufactorers" were working out of their garage. As long as they think you are serious and responcable they may be willing to help you. Try to have a plan when you talk to them. Start documenting and building files. Develop paper work to record your testing and gather real data. Graphs in a computer always impres people. I think you'll find that if they have faith in you they will bend over to help you.

What times of the day are you around? I've been trying to keep an eye on skype but you always seem to be off line.

Lee


(This post was edited by RiggerLee on Dec 4, 2012, 11:10 AM)


JerryBaumchen  (D 1543)

Dec 4, 2012, 11:49 AM
Post #78 of 243 (3926 views)
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Hi Quagmirian,

Quote:
by recognised parachute equipment manufacturers

Typical bureaucratic horse-puckey IMO.

1. Who would be doing the recognizing?
2. What are the criteria to be a parachute equipment manufacturer?

If you sewed it then ( IMO ) you are the parachute equipment mfr.

What a way to stifle progress.

Crazy

JerryBaumchen


HUPRA  (D 5203)

Dec 7, 2012, 1:44 AM
Post #79 of 243 (3795 views)
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In reply to:
I had a very productive conversation with J Wragg; he answered a lot of my questions and make me think about a few things that hadn't crossed my mind. I may have hit a snag as far as testing goes, see the BPA ops manual:

"Parachutes may only be used if they are manufactured for Sport Parachutists or Military Parachutists, by recognised parachute equipment manufacturers or riggers with the necessary qualifications."

However:

"BPA A Licence parachutists and above may perform cutaways (at a club PLA/DZ) with a cutaway `rig designed for the purpose, provided they have CCI permission and have been thoroughly drilled in the cutaway procedures."


So technically I could do a cutaway jump on my A licence, but I'd have to leave the test jumping for someone else for now.

Is the offer of 100 quid to anyone at the DZ that jumped your canopy still standing?

I might jump it, damned if I'll try and land it though......Smile


Quagmirian  (A 110392)

Dec 7, 2012, 2:39 AM
Post #80 of 243 (3787 views)
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Yes, the offer of 100 quid's worth of free drinks still stands, although you must land the canopy too.Wink


Clouddancer22  (D 11672)

Dec 7, 2012, 8:14 AM
Post #81 of 243 (3754 views)
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And video too please!!! Smile I have really enjoyed this thread, standing on edge to see the outcome. I have manufactured experimental canopies from the Navy and gotten to video their openings. Cool stuff!


Quagmirian  (A 110392)

Dec 11, 2012, 2:34 PM
Post #82 of 243 (3649 views)
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Does anybody know what 400 lb dacron looks like? I nicked the stuff I have off an old swift reserve, R3 1660, Nov 1982, but it looks to be completely different stuff to what I'm seeing elsewhere. Help?


indyz  (D 28525)

Dec 11, 2012, 3:21 PM
Post #83 of 243 (3634 views)
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There are two kinds of dacron that you are likely to see, flat braided and round braided. Flat dacron looks, well, flat, like a shoe lace. Flat dacron isn't commonly used on newer sport parachutes, but it was used on Swifts and many other canopies in the 80s and early 90s. 600 lb and stronger round dacron is pretty common on sport canopies but I've only seen 400 lb used on low-volume BASE canopies like the Flik Lite and the Feather.


RiggerLee

Dec 11, 2012, 3:39 PM
Post #84 of 243 (3627 views)
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This is a base canopy thing but keep in mind that they did pop a couple of 400 lb center cascaded a/b lines on a base jump, see the fatality report. So it's getting a bit minimal for that location.

Lee


Quagmirian  (A 110392)

Dec 12, 2012, 5:49 AM
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Poynter's manual does say that 400 lb is the minimum for any sport canopy, and centre lines should be stronger than that. The only reason I'm using it for the suspension lines is because it's what I've got, it makes sense to use what I have. This model probably will never see the sky anyway, and if it does, it won't be going to terminal. I will strengthen the centre lines anyway though, as good practice.

Anyway, I have been experimenting with the bottom loaded rib seams. I am going to be putting a piece of 3/8" type III along the whole length of the seam, and that, coupled with the leading edge tapes and line attachments will make my traditional rolled seam unacceptably thick. I am considering a spanwise lower skin to simplify and thin out this seam. Here are some pictures. Apologies for the crappy quality, these were taken with my button camera.
Attachments: AK000015.JPG (146 KB)
  AK000017.jpg (121 KB)


voilsb  (D 30581)

Dec 12, 2012, 6:10 AM
Post #86 of 243 (3556 views)
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I've got my canopy lined with 350 dacron, 400 dacron on the brakes. I can take some pictures of the lines next time I have it open if you'd like.


Quagmirian  (A 110392)

Dec 14, 2012, 1:16 PM
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Please do take some pictures. I thought I had my head round what kind of lines there are, and now I have no idea. Here is a picture of what I have. The 400 lb Dacron I bought is on the left, with the narrower, thicker stuff on the right. Any ideas?
Attachments: AK0000181.jpg (172 KB)


indyz  (D 28525)

Dec 16, 2012, 10:57 PM
Post #88 of 243 (3338 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

The stuff on the left looks like flat dacron, similar to ParaGear part number W9754F. The stuff on the right could be a lot of things. Where did you get it from?


Quagmirian  (A 110392)

Dec 17, 2012, 6:47 AM
Post #89 of 243 (3305 views)
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Re: [indyz] My little project [In reply to] Can't Post

As I said, I got it off an old swift reserve, R3 1660, Nov 1982. It's almost the same size as 725 spectra if that's any help.


Quagmirian  (A 110392)

Dec 22, 2012, 2:27 PM
Post #90 of 243 (3169 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

No ideas on what the line is then? I've sent it back to the shop, they'll probably know anyway.

The good news is I've had some luck with my bottom seams. I've switched to some lighter reinforcement tape (no idea what it is either), and I managed to make the difficult bit at the leading edge, line attachment included. I think I'm going to go for spanwise construction on the bottom skin to minimise bulk in this area.

Attached is some pictures of this and my proposed seams. I'm running a piece of reinforcement tape completely along the loaded bottom seams.

Input appreciated
Attachments: AK000025.JPG (160 KB)
  AK000026.JPG (164 KB)
  AK000027.JPG (161 KB)
  seven cell seams new.png (13.3 KB)


RiggerLee

Dec 22, 2012, 9:09 PM
Post #91 of 243 (3128 views)
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I'm guessing you've picked up some kind of roll attachment. Just for the record you can probable go simpler. Loaded rib top seam, you can probable get by just sewing the stack togather as long as you have a bit of excess on the out side. Loaded rib bottom seam, I think you could use one less roll, so just an up fold. You might try baisting the tape on the rib to make it easy. Un loaded ribs, again I think you could just sew it down as long as there is a bit of excess beyond the seam. Stabalizer, Again I think one fold is enough. this all assumes you are hot cutting every thing. In the past we did put in extra folds, try to hide edges, and all that. Now that we're hot cutting every thing we're getting lazy and for the most part finding that it's strong enough. There have been a few time we've gone to far. As an example, Germain tryed something fucked up for a while. Eventually the ribs just came loose. It was just an over lap of the top skins and the ribs. He might have gotten away with it if he's had more seam allowance but it just pulled out at the two edges. Knew a guy with an old Jonithen like that. But honestly you're makeing it a bit hader then necasary.

Lee


Quagmirian  (A 110392)

Jan 6, 2013, 2:06 PM
Post #92 of 243 (2945 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

Ok, after lots of swearing at my sewing machine, I may have decided on my bottom seams (picture attached). Even though I am hot cutting all my pieces, I really don't like the idea of raw edges, as the poorly cut material my saw into the rest of the fabric. I've come to a compromise of sorts. The bottom skin will be spanwise constructed, the top skin chordwise. This should maximise what little strength I have as well as keep the loaded bottom seam thin. It's not folded, but because it's a spanwise panel there are no raw edges either. I am going to put a piece of 3/8" type 3 for the full length of all the loaded bottom seams, and I may lightly reinforce spanwise too.

I've just finished making a modification to my crappy white thing, I was replacing the stabiliser to test the design. Turns out I need to take line attachment and seam height into account. Blush I don't have any pictures yet, but when I do I'm sure you'll all be impressed and you can send my master rigger's rating in the post.Wink
Attachments: seven cell seams new2.png (13.1 KB)


unkulunkulu  (C License)

Jan 6, 2013, 3:54 PM
Post #93 of 243 (2902 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Sorry if someone already asked this, but I've read this thread and I'm very curious, what is your background/education? How do you know things not only about aerodynamics, but about this sewing stuff, you know :) Wish you success in your passion :)


Quagmirian  (A 110392)

Jan 6, 2013, 5:01 PM
Post #94 of 243 (2879 views)
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I don't know anything about aerodynamics or sewing.


ChrisD  (No License)

Jan 6, 2013, 5:21 PM
Post #95 of 243 (2867 views)
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In reply to:
I don't know anything about aerodynamics or sewing.

Dude you obviously know which way the pointy end faces! And you know how to get the sewing machine started, dosen't look like hand stitching to me! You rock!

It's just that no one wants to see you end up like: Piltre de Rozier and Pierre Romain. And I suspect more than a few, including me...wish we were as determined/ or as adventerous as you...
C


Quagmirian  (A 110392)

Jan 14, 2013, 10:11 AM
Post #96 of 243 (2738 views)
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Re: [ChrisD] My little project [In reply to] Can't Post

Here's some pictures of the modification I made. Not much to see, but now when it's folded up it goes inside a bag.
Attachments: mod10.jpg (217 KB)
  mod20.jpg (241 KB)


Quagmirian  (A 110392)

Jan 24, 2013, 4:47 AM
Post #97 of 243 (2594 views)
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Ok, here we go again. I've decided that I really liked my last model, nd I'm going to bring back the airfoil, with a few improvements. It's still got a thickness of 16% and the basic shape is still there, but I've smoothed it out a bit in an attempt to improve performance. I've also steepened the leading edge inlet by about five degrees.

As for the seams, they're about as simple as you can get, and according to RiggerLee, I should be able to get away with them, for a few jumps a least. They'll also be super easy to mark and sew.

I've drawn up a stabiliser, based on the predicted line lengths, this time taking into account the length of the bottom seam, tape and lark's head knot. The line trim will probably change, but now I know that I can replace the stabilisers on the finished model if I need to.

I haven't drawn any patterns yet, and I'm interested to hear what people think about this.
Attachments: smallest rib redesign.gif (4.85 KB)
  seven cell seams new3.png (7.55 KB)
  rib and stab.gif (4.46 KB)


RiggerLee

Jan 24, 2013, 2:27 PM
Post #98 of 243 (2523 views)
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Keep in mind that they leave a bit of edge beyond the last row of stitching on the unloaded and top skin. On the bottom I might sew the tape a bit higher with the top seam and then tuck the three edges on the bottom under and sew the last line. That's one of the heavier load points. You could use a wider tape there if you needed to. You might want to have you're B line slider stop at least as low as the A line Or make sure to put a stop on the outer A. A's like to shrink and pull through the grommets. You can get functions that way depending on how you build the attachments.

Lee


Quagmirian  (A 110392)

Mar 2, 2013, 5:29 PM
Post #99 of 243 (2320 views)
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In reply to:
Car-towing a ramair canopy is a pretty stupid idea. Don't do that.
Can someone give me an outline of why this is a bad idea and what can go wrong?

Anyway with over half my parts cut out and and a bit of sewing done, it's about time I show off my design.



This canopy will probably never fly, but if anything this project has at least opened my eyes to how much stuff there is to know about parachute design.
Attachments: parts.gif (7.23 KB)


sundevil777  (D License)

Mar 2, 2013, 5:47 PM
Post #100 of 243 (2302 views)
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In reply to:
In reply to:
Car-towing a ramair canopy is a pretty stupid idea. Don't do that.
Can someone give me an outline of why this is a bad idea and what can go wrong?

The danger is from what is called "lockout"

From this website:

http://home.clara.net/...wiz/towfaq_frame.htm

Quote:
Q. What is lockout?

When going up the line, it is imperative that you do the "noddy dog routine". As you get higher there is a distinct possibility that the wind direction will change slightly or that you will be pulled through a thermal. As this happens the wing will turn away from the winch. If you don't watch what the wing is doing, this turning will eventually result in a lockout as a direct result of being pulled through the air. The wing will be so far off the 90 degree angle to the winch you won't be able to get it back on course. Think of a kite when it turns over in the air and heads for the ground in a strong wind. The only way the pilot can get out of a lockout is to get off the tow line. But since he/she would be struggling with the brakes and worrying about how hard they are going to hit the deck, there won't be much time to find the release. A good winch driver will save the day by cutting the line and allowing the pilot to recover the wing and then release the tow line. An even better winch driver will see the pilot flying off course and will reduce the power. When the wing comes back on course he will apply the power again.


(This post was edited by sundevil777 on Mar 2, 2013, 5:55 PM)


riggerrob  (D 14840)

Mar 3, 2013, 3:41 PM
Post #101 of 243 (4134 views)
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Re: [sundevil777] My little project [In reply to] Can't Post

Definitely install a 3-Ring release at the top end of the tow-line. Then install the 3-Ring release handle some place it is really easy to grab (e.g. chest level) on the harness.


riggerrob  (D 14840)

Mar 6, 2013, 5:58 PM
Post #102 of 243 (3980 views)
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In reply to:
Definitely install a 3-Ring release at the top end of the tow-line. Then install the 3-Ring release handle some place it is really easy to grab (e.g. chest level) on the harness.

........................................................................

"Towing Aloft" by Dennis Pagen and Bill Bryden
1998
ISBN 0-936310-13-8

or contact your local chapter of the British Hang-gliding Association or the British Para-Gliding Association or the British Parascending Association.


Quagmirian  (A 110392)

Mar 22, 2013, 3:38 PM
Post #103 of 243 (3833 views)
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Got my first topskin and NLB cut out so I did the I beam work on the centre cell, and well as the bridle attachment and reinforcements. Not much to see from the shitty pictures but I have a feeling this is going to be a good kite.

Also note the hilarious comedy warning label.



Attachments: AK000031.JPG (34.0 KB)
  AK000035.JPG (42.4 KB)


chuteshack

Mar 23, 2013, 9:58 AM
Post #104 of 243 (3757 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

the dacron you got from your swift reserve was a custom braid made by FWF Industries . FWF is no longer in business as the founder , freeman w frame died several years ago.


Quagmirian  (A 110392)

Mar 24, 2013, 8:38 AM
Post #105 of 243 (3667 views)
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In reply to:
the dacron you got from your swift reserve was a custom braid made by FWF Industries . FWF is no longer in business as the founder , freeman w frame died several years ago.
Thanks for the info. I assume that any quantity will be a rarity nowadays then.


Quagmirian  (A 110392)

Apr 16, 2013, 4:30 PM
Post #106 of 243 (3487 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Five and a half cells sewn together and side stacked (you'll just have to believe me I'm afraid, the picture isn't very clear).


Attachments: AK000010.JPG (47.1 KB)


Quagmirian  (A 110392)

Apr 21, 2013, 9:07 AM
Post #107 of 243 (3305 views)
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Entire canopy finished, apart from some real dacron lines it's good to go. The trim is awfully steep, with all the pressure on the front risers. Very easy to ground handle though.Smile







Attachments: DSC_0159_small.jpg (108 KB)
  DSC_0160_small.jpg (97.7 KB)
  DSC_0161_small.jpg (105 KB)
  DSC_0162_small.jpg (96.5 KB)
  DSC_0163_small.jpg (96.6 KB)
  DSC_0166_small.jpg (174 KB)


RiggerLee

Apr 21, 2013, 1:39 PM
Post #108 of 243 (3276 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Are your b-line slider stops lower on your line set then your a-line attachments? If not you may find your a-line tapes being sucked into your grommets. You might have to add a stop on the A-line. pic 2 makes it look like you might still be just a little narrow on the panels towards the front of your canopy. It's hard to tell with the risers crossed and control input on the rears. You say it's steep? Relitive to what? and why go that way? By the way I think your better off a little steep then a little flat, assuming with in reason. Flat canopies can be short on flare authority with out front riser or extra speed.

Got a rig set up yet to jump it? Have you been thinking about the testing you want to do before you eventually commit to landing? By the way, even a small sand bag weight clipped to a toggle will go a long way to bringing the thing down with minimal drift.

Lee


HUPRA  (D 5203)

Apr 22, 2013, 6:46 AM
Post #109 of 243 (3205 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Nice work! I say stick a tandem dummy on the bottom of it and throw it out the aircraft with someone holding the D-bag, and get a vid of it....


JerryBaumchen  (D 1543)

Apr 22, 2013, 1:01 PM
Post #110 of 243 (3152 views)
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Hi Quag,

Quote:
Entire canopy finished


From someone who built his own canopy, I applaud your accomplishment.

Particularly, when you are someone with 83 jumps & one year in the sport.

It sure looks like you just might know what you are doing.

Cool

JerryBaumchen


Quagmirian  (A 110392)

Apr 22, 2013, 3:07 PM
Post #111 of 243 (3123 views)
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Re: [JerryBaumchen] My little project [In reply to] Can't Post

Thanks Jerry, although I think if you saw the canopy up close you wouldn't want to jump it. I still have much to work on before I will have something airworthy.

Here are a few pictures without the risers crossed.



Attachments: DSC_0164.JPG (670 KB)
  DSC_0165.JPG (663 KB)


JerryBaumchen  (D 1543)

Apr 22, 2013, 3:14 PM
Post #112 of 243 (3118 views)
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Hi Quag,

And here is another home-built one:

http://vimeo.com/64373524

Is there a home-built fad going around that I am not aware of?

Tongue

JerryBaumchen


Maksimsf  (B 37743)

Apr 22, 2013, 3:58 PM
Post #113 of 243 (3107 views)
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Re: [JerryBaumchen] My little project [In reply to] Can't Post

In reply to:
Hi Quag,

And here is another home-built one:

http://vimeo.com/64373524

Is there a home-built fad going around that I am not aware of?

Tongue

JerryBaumchen

If the prices of mains will keep climbing up - we will see more and more DIY Cool


Premier NWFlyer  (D 29960)

Apr 22, 2013, 4:09 PM
Post #114 of 243 (3099 views)
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Re: [Maksimsf] My little project [In reply to] Can't Post

In reply to:
In reply to:
Hi Quag,

And here is another home-built one:

http://vimeo.com/64373524

Is there a home-built fad going around that I am not aware of?

Tongue

JerryBaumchen

If the prices of mains will keep climbing up - we will see more and more DIY Cool

Probably not... most skydivers are far too lazy for that!

Me, personally, I value my time too highly to even consider a DIY project - of course, I'm just not interested enough to geek out on it like some folks do. I give Quagmarian lots of credit for spending the time to do this, and it sounds like he's enjoyed the process as much as anything - but I'd be willing to bet that if he added raw material cost and total time spent to get it safely airworthy (which it sounds like it might not be yet) that buying almost any canopy from any manufacturer, even brand new, will turn out to be a better deal. LaughLaugh


shibu  (B 37474)

Apr 23, 2013, 9:26 AM
Post #115 of 243 (3036 views)
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Re: [NWFlyer] My little project [In reply to] Can't Post

In reply to:
In reply to:
In reply to:
Hi Quag,

And here is another home-built one:

http://vimeo.com/64373524

Is there a home-built fad going around that I am not aware of?

Tongue

JerryBaumchen

If the prices of mains will keep climbing up - we will see more and more DIY Cool

Probably not... most skydivers are far too lazy for that!

Me, personally, I value my time too highly to even consider a DIY project - of course, I'm just not interested enough to geek out on it like some folks do. I give Quagmarian lots of credit for spending the time to do this, and it sounds like he's enjoyed the process as much as anything - but I'd be willing to bet that if he added raw material cost and total time spent to get it safely airworthy (which it sounds like it might not be yet) that buying almost any canopy from any manufacturer, even brand new, will turn out to be a better deal. LaughLaugh

Right. You really have to love doing something like this to do it. It will feel great to fly something you built with your own two hands.

It would be great to see jumpers who are also aerospace engineers do projects like this. It's possible they could come up with some design improvements.


shibu  (B 37474)

Apr 23, 2013, 9:30 AM
Post #116 of 243 (3031 views)
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Re: [JerryBaumchen] My little project [In reply to] Can't Post

In reply to:
....And here is another home-built one:
http://vimeo.com/64373524
....

It must really suck to chop after you put all that effort into making it.


JerryBaumchen  (D 1543)

Apr 23, 2013, 12:08 PM
Post #117 of 243 (3004 views)
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Hi shibu,

In reply to:
In reply to:
....And here is another home-built one:
http://vimeo.com/64373524
....

It must really suck to chop after you put all that effort into making it.

Not to be negative towards you, but if that is your thinking then I would suggest that you never work in Research & Development; it comes with the territory.

JerryBaumchen
Someone who blew two harnesses completely apart during TSO testing


JerryBaumchen  (D 1543)

Apr 23, 2013, 12:12 PM
Post #118 of 243 (2999 views)
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Hi Kris,

Re: I value my time too highly to even consider a DIY project

And here I thought you had somone in your life who is buying sewing machines right & left.

Tongue

JerryBaumchen


Squeak  (E 1313)

Apr 27, 2013, 7:33 AM
Post #119 of 243 (2933 views)
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Re: [JerryBaumchen] My little project [In reply to] Can't Post

In reply to:
Hi Quag,

And here is another home-built one:

http://vimeo.com/64373524

Is there a home-built fad going around that I am not aware of?

Tongue

JerryBaumchen

that's Nik Burden he makes base containers too, it's a little more than standard DIY with Nik.WinkWink


JerryBaumchen  (D 1543)

Apr 27, 2013, 2:23 PM
Post #120 of 243 (2900 views)
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Hi Squeak,

Quote:
that's Nik Burden

Nik and I have been sharing info for a couple of years now; even met his mother last year.

JerryBaumchen


Quagmirian  (A 110392)

May 6, 2013, 2:52 PM
Post #121 of 243 (2787 views)
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I took the brown thing for its first flight today, a ground launch. No pictures I'm afraid.Frown I sorted out the stability problem I was having by flattening the trim by a few inches. The flight performance was amazing; I must have had a glide ratio of at least 1.5 to 1.Smile The landings were less than perfect, but the flare had a lot of power and heavy toggle pressure, just the way I like it. If this ever ever gets jumped, it's shaping up to one hell of a good wing.


potatoman  (Student)

May 8, 2013, 3:30 AM
Post #122 of 243 (2715 views)
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Brown Thing....Maybe that could be the name of a nice new canopy.......150BT.

Go jump the darn thing.....Better yet, build a hot air balloon, and then go jump out of that with your BT.

(Make sure you gots a TSO'd reserve....)

Well Done!!!


Quagmirian  (A 110392)

May 11, 2013, 3:48 PM
Post #123 of 243 (2602 views)
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So I said there weren't any pictures from Monday, well, that's not quite true.



I don't know if it's coming off in these posts, but all the study and work is worth it for moments like this. You'll notice I wore a helmet and gloves this time.Wink
Attachments: 5th_pic.jpg (440 KB)


Quagmirian  (A 110392)

May 14, 2013, 3:53 PM
Post #124 of 243 (2472 views)
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Here's a photo highlighting the topskin. I think it looks nice and smooth.


Attachments: topskin.jpg (505 KB)


Quagmirian  (A 110392)

May 21, 2013, 8:17 AM
Post #125 of 243 (2267 views)
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...but maybe not smooth enough. Here's an idea for a new rib and stabiliser, similar to the brown thing but with a few changes. The airfoil's a bit thinner, the nose opening's a bit smaller and steeper and the line trims are based on the brown thing after re trimming. I've also moved some of the V-tapes in an attempt to make the top skin perfectly smooth.


Attachments: 2732_rib_stab_small.gif (13.6 KB)


ChrisD  (No License)

May 21, 2013, 8:40 AM
Post #126 of 243 (4370 views)
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Smile

You would think that there is some kind of computor program that would enable you to understand the effects of subtle changes in canopy configurations?

There isn't.

Therefore, keeping safety foremost in mind, everyone's comments early on in your postings, the good, the bad, the rude,...all apply.

You might just stumble upon something new and for that:

once again I applaud your efforts!Wink


JerryBaumchen  (D 1543)

May 21, 2013, 12:29 PM
Post #127 of 243 (4325 views)
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Hi Quag,

Something that occured to me: Why not spread the rib/support tapes where they top out on the rib? This might spread the load(s) somewhat for a smoother topskin. As they are, they are point loading where they intersect.

Just something to consider,

JerryBaumchen


Quagmirian  (A 110392)

May 21, 2013, 1:11 PM
Post #128 of 243 (4302 views)
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JerryBaumchen wrote:
Why not spread the rib/support tapes where they top out on the rib? This might spread the load(s) somewhat for a smoother topskin.
From what I can gather, it seems to be a bit of a trade off. If I spread the tapes out too much, I think I will end with something like this:



Taking it to the extreme, if the tapes were infintely close together, ie one tape going straight up, it would look like this:



I have moved just the c1 and d1 v tapes back a few inches, so I should end up with something like this:



From my not very extensive studies, I have decided that I am more afraid of tapes being too far away from each other than too close. I'm sure you'll agree that all this isn't going to make too much of a performance change anyway, since I am working on relatively large, conservative 7 cells. Feel free to overrule me on this if you feel I've missed something.
Attachments: pd_reserve_small.jpg (30.7 KB)
  300652_small.jpg (27.1 KB)
  trango_small.jpg (29.6 KB)


JerryBaumchen  (D 1543)

May 21, 2013, 3:02 PM
Post #129 of 243 (4281 views)
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Hi Quag,

Quote:
Feel free to overrule me on this if you feel I've missed something.

Nope, it was just a suggestion. Heck, I didn't even charge you for it. Cool

"Overrule you." Never, it is after all your project.

JerryBaumchen


Quagmirian  (A 110392)

May 21, 2013, 5:36 PM
Post #130 of 243 (4244 views)
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JerryBaumchen wrote:
Quote:
Feel free to overrule me on this if you feel I've missed something.
"Overrule you." Never, it is after all your project.
That may be, but I'd rather you say something before I make any shitty design choices.


Quagmirian  (A 110392)

May 24, 2013, 6:44 PM
Post #131 of 243 (4093 views)
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I thought I'd share this little gem from Poynter's.


Attachments: slope_soaring.gif (167 KB)


Quagmirian  (A 110392)

Jun 10, 2013, 2:28 PM
Post #132 of 243 (3991 views)
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Here's something I forgot to post a while back. While it is beyond the scope of this project to manufacture live risers, I have been making some for ground handling and launching. Here's my latest effort (it's actually quite old) compared to a bought, and I suspect rigger made, riser. My thoughts so far? Accurate three ring riser construction is difficult and best left to manufacturers. I will not be jumping home made risers, as I consider them part of the H/C system.



Recently, I have been doing a lot of 'thinking'. While I am very happy with the performance of the brown thing, I think I can do better, particularly in the flare department. I have redesigned my ribs with smaller nose inlets and smoother profiles, in an effort for better glide and flare power.

One other thing, from now on I will be building canopies with fixed aspect ratios and at recognised sizes. While in the past I have made wings with areas of 'about 160-170 square feet', I will now stick as accurately as possible to known sizes, as in 135, 150, 170, 190 etc.

Here are the redesigned ribs, both seven and nine cell versions, in this case for a 150 square foot canopy.






(This post was edited by Quagmirian on Jun 10, 2013, 2:40 PM)
Attachments: 150-2571_small.gif (12.5 KB)
  139-2362_small.gif (11.5 KB)
  3_rings.JPG (61.7 KB)


bofh  (D 13995)

Jun 13, 2013, 5:04 AM
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Quagmirian wrote:
Recently, I have been doing a lot of 'thinking'. While I am very happy with the performance of the brown thing, I think I can do better, particularly in the flare department. I have redesigned my ribs with smaller nose inlets and smoother profiles, in an effort for better glide and flare power.

Have you seen Ozone's patent for SharkNose? It would be interesting to see how that concept would work on a parachute:
http://downloads.flyozone.com/...ne_shark_nose_en.pdf


Quagmirian  (A 110392)

Jul 11, 2013, 2:04 PM
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bofh wrote:
Have you seen Ozone's patent for SharkNose? It would be interesting to see how that concept would work on a parachute:
http://downloads.flyozone.com/...ne_shark_nose_en.pdf
Thanks for that. I think that sort of thing is out of my skill level at the moment. Maybe when I'm building a high end swooping canopy, I'll come back to it.

I have been doing some more thinking, and I have decided that I want to put a single fold on the loaded bottom seams, not because it's any stronger, but because it looks a bit more professional. I've also changed my trim, rib and stabilser panels again.





I decided to use my scraps of old dacron to replace and extend my upper steering lines. It wasn't too difficult and they're all the same length +/- 0.25 inches. Good practice and now I have nice looking control lines. Smile








(This post was edited by Quagmirian on Jul 11, 2013, 4:13 PM)
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  AK2.JPG (71.3 KB)
  AK3.JPG (80.1 KB)
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  2742_rib_flat_small.png (29.1 KB)


Quagmirian  (A 110392)

Jul 25, 2013, 1:35 PM
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No more production updates for the moment, as I am living in the countryside for my own health. I have found a few good ground launching spots though.




Attachments: DSCF1007_small.jpg (313 KB)
  DSCF1008_small.jpg (546 KB)


Quagmirian  (A 110392)

Aug 10, 2013, 8:30 AM
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I have done quite a few flights on this thing now, including a glide down a 500 ft high slope, which was great fun. I have come to some general conclusions about the canopy in its current configuration.

Glide ratio is nice and flat, around 2.5:1.
Front riser pressure is very high.
Rear riser pressure is low, with a small control range before the stall (about 4 inches).
Flare power on the toggles is very good for a canopy of this size and type.
Control range on the brakes seems to be decent, although I haven't stalled it on the toggles yet.


Quagmirian  (A 110392)

Aug 20, 2013, 2:41 PM
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I've been doing a lot more ground launching. I went flying yesterday and it was very windy on the hill, so I got a decent bit of air time riding the rising air. I even got so bold as to try and stall the canopy. It didn't fold back on me, but it didn't look very happy either.

I took the canopy flying today with a couple of cameras. Here are some frames from the foot mounted camera.







This frame was captured just before landing, with the canopy in deep brakes.


Moving on the the future, here's a comparison of the rib sections and planforms of my old design, current canopy, and new design.





Comments and criticism are always welcome.
Attachments: frame1.png (230 KB)
  frame2.png (196 KB)
  frame3.png (183 KB)
  frame4.png (184 KB)
  planforms_small.png (8.05 KB)
  ribs_compare_small.png (28.1 KB)


Quagmirian  (A 110392)

Sep 2, 2013, 5:41 PM
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I've been going backwards and forwards on a few little things, but I think I finally have a design to replace the brown thing. The main design difference is the rib section, which is slightly thinner and smoother, with a smaller nose cut. There are construction differences too, addressing structural and quality issues.

General canopy info
Cells: 7
Aspect ratio: 2.10
Area: 170 sq ft
Chord: 2.740 m (8.99 ft)
Span: 5.754m (18.88 ft)
Colour: Not yet known, orange perhaps
Lines: 600 lb Dacron

Rib section
Max thickness: 15.0%
Position of max thickness: 19.4% (same as brown thing)
Nose cut size: 8.54%
Nose cut angle: 142

Slider, standard
Chord: 0.44m (17.3 inches)
Span: 0.78m (30.7 inches)
Grommets: Brass, type 8

Line trims (mm)
A line 3108
A-B 66
A-C 216
A-D 458
UST 1200
LST 2716 Roughly
BK-TOG Don't know yet

Panel shapes (less seam allowance) and slider diagram


Attachments: parts.png (22.6 KB)


RiggerLee

Sep 2, 2013, 6:20 PM
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The "Orange Thing"? I'm sencing a trend here. Your doing well on your design and Ok on your construction, but you need to work on your marketing. Take my word for it. Cool names and half necked woman, you can sell any thing that way.

Lee


mr2mk1g  (C 103449)

Sep 3, 2013, 3:06 AM
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Just so you know, whilst you might not be getting many replies recently, we are still reading and interested in your projects. It's great to read of someone 'mucking about' like this.


DHemer  (B License)

Sep 3, 2013, 4:06 AM
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Keep it up
Enjoy reading the updates


shropshire  (C License)

Sep 3, 2013, 5:05 AM
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mr2mk1g wrote:
Just so you know, whilst you might not be getting many replies recently, we are still reading and interested in your projects. It's great to read of someone 'mucking about' like this.

Very true..... Keep going OP


skyturtle

Sep 3, 2013, 12:38 PM
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Just out of interest, how did you work out the dimensions for your slider or is it just a temporary design?


Quagmirian  (A 110392)

Sep 3, 2013, 2:39 PM
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skyturtle wrote:
Just out of interest, how did you work out the dimensions for your slider or is it just a temporary design?
The measurements are based on the slider from a PD 7 Cell. When I get round to jumping this thing we can work out if the dimensions need to be changed. It's just a starting point.


Quagmirian  (A 110392)

Sep 6, 2013, 7:10 PM
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I'm happy with all the seams on the brown thing, except the loaded bottom seams. Even if I hot cut everything, stuff still sticks out and I don't like the look of the raw edges. Also, the flat seam looks a bit thin in places. I would fold or roll the seam but all the bulk at the leading edge makes it very hard for my puny machine to sew properly, so I've come up with a solution. When I apply the leading edge tapes to the bottom skin and rib, I pre-fold the edges so that the tape only has one layer of thickness. It's difficult to explain so I hope this diagram helps.



I've made an image of what the new canopy should look like based on the brown thing in flight.


I've also decided on a warning label design and stabilser logo panel.




Attachments: seams.png (10.4 KB)
  new_7_cell.png (20.2 KB)
  warning_label1_small.png (92.9 KB)
  canopy_logo_9a_small.png (23.0 KB)


pwilliams  (A 64668)

Sep 11, 2013, 12:55 PM
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Love this thread, please continue to keep us updated Wink


Quagmirian  (A 110392)

Sep 12, 2013, 1:11 PM
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There are a few things I don't like about the brown thing. Firstly, the control range is a bit short on the toggles (it's a flat trimmed canopy), and secondly, the turns are a bit snappy after about half brakes. There's plenty of flare power and toggle pressure though, so I thought I'd try and solve these problems by moving the most inboard control line half a cell outboard, like this:



Any thoughts?
Attachments: new_ust_config.png (14.0 KB)


Quagmirian  (A 110392)

Oct 8, 2013, 4:57 AM
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I had a go at making a slider for my new project.


Attachments: AK000003.JPG (44.7 KB)


theonlyski  (D License)

Oct 8, 2013, 8:05 AM
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Quagmirian wrote:
There are a few things I don't like about the brown thing. Firstly, the control range is a bit short on the toggles (it's a flat trimmed canopy), and secondly, the turns are a bit snappy after about half brakes. There's plenty of flare power and toggle pressure though, so I thought I'd try and solve these problems by moving the most inboard control line half a cell outboard, like this:



Any thoughts?

If I recall correctly, that's the exact opposite of the Triathalon mod (it goes from the "After" to the "Before" IIRC)


Quagmirian  (A 110392)

Oct 19, 2013, 5:21 AM
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That sounds about right.

I downloaded Javafoil and put my airfoil in it and I have no idea what I am supposed to be looking for.


Attachments: javafoil.png (94.2 KB)


darkwing  (D 4164)

Oct 19, 2013, 4:13 PM
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Stall tests [In reply to] Can't Post

Close to the ground is a very risky place to do stall tests on experimental canopies.


Quagmirian  (A 110392)

Oct 20, 2013, 5:00 AM
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darkwing wrote:
Close to the ground is a very risky place to do stall tests on experimental canopies.
Yes, well, I do lots of stuff I shouldn't really do. At least now I know the stall point I can fly more confidently and work to make improvements.

Someone just happened to be walking by when I was launching the other day and took these interesting but not necessarily useful pictures.








Attachments: small1.jpg (116 KB)
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  small2.jpg (96.5 KB)


RiggerLee

Oct 20, 2013, 11:02 AM
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I lost my reply so I'll try again.

I'll toss out a few thoughts of what you might learn from a peace of soft ware like that.

The first is a warning to try and keep in mind exactly what it is and to try and anticipate it's limitations. All models have a point at which they fail. They are all bullshit straight out of some bodies ass. At best you can hope that they have a passing resemblance to reality over some small range.

As an example, the nose cut. I'm guessing that it's seeing it as a flat plate with no flow across the surface. Well that's not true. Even if it were I'd still be a little suspicious of the sharp corners. That's not to say that it's not interesting. It shows very well a preasure gradient across the nose opening. A fairly significant one. You can see how air will flow in through the bottom half of the nose and out through the top. That in it self would fundamentally change the flow around the model so you know there are errors there. But it does give you an idea of how you might be able to change the nose cut or add a lip to the canopy. Ideally the opening would be right at that purple spot near the bottom.

But that is just one AOA. If you look at how that changes as the AOA changes you can get an idea of how much lip you could get away with on a canopy. At a shallower angle you don't want the higher pressure to shift too far above the lip or onto the edge of the top skin. That's where you start to get a dimple and in the most extreme cases a leading edge collapse. Remember that the model is breaking down there and that this feeds back into it self. I'm not saying that it can't tell you things just that you have to keep in mind that it's at best a rough cut.

The tail is another place that I'd expect some error. Remember it wants to inflate and become rounded over most of the span. If I was to take a guess I'd expect a higher drag from this then you see in the model. Same thing at the nose. It will be draggier then this model.

Having said all that I would expect the lift and CP to be about on. Drag should be at least workably close. What it give you is something you could maybe use as a starting point for a finite wing. What you have there is two dimensional. It's actually no where close to the performance of the canopies wing. With the AR as low as it is the drag of the canopy will be dominated by the induced drag of the wing. Our glide angles suck and it's mostly because of the aspect ratio being under three. To really get any idea of the performance or behavior of the canopy you'll have to look at it as a finite wing. Bad news is that the problem is an order of magnitude harder then that little 2D app. I don't know if you can find any free software out there that can really do it. There might be some hope. There are a few old school approximations out there that might give you something. You could try looking at it with some form of "lifting line theory". Basically it looks at the wing as a sheet of vortexes shed by each section of the span of the wing. It's a way of looking at how each of the sections affects the local AOA of all the other sections. You wind up with this big pile of interlocking equations that go into a big matrix... it's not real pretty. But at least under certain circumstances a computer can muddle it's way through it. I want to say that we did program for... I think it was a tapered twisted wing. It's a standard assignment for undergrads but it's been many a year. You might be able to find some thing out there for free that would give you some thing you could work with. Some thing like a vortex lattice would give you an idea of the induced drag but I'm not sure about the aspect ratio. Normally people look at longer wings then this. It's more reasonable to model some thing like that as a line through the ac. A model like that might tend to break down with such a low aspect ratio wing. If you're going to run in to any problem with something like this it would probable be there.

Another issue is the anhedal angle of the wing. If your lines are long enough you might just be able to ignore it. Let's say that at your trim angle at your normal glide that the angle of attack to the free stream is constant along the span of the wing. I think you could dismiss the curvature for an analysis like this and then look at it separately in terms of the loss of lift due to the curve. In other words bend the wing after you analyze it. At this point you should be able to do a stedy state for that AOA. For that AOA it would give you a lift, drag, L/D and CP. That should let you do a very good guess at a trim for a line set that would give you that AOA and glide.

Once you work that out as your steady state trim angle I think you could look at pitching the canopy from that by looking at the local AOA at each section of the wing as the curved wing pitches. You could then treat it as a twisted wing for the analysis at that perturbed angle of attack. In that way I think you could start looking at things like the pitch stiffness of the canopy and maybe some of it's dynamic characteristic's.

What I'm describing is awfully rough and crude and at times a slight missuse of some of these models but I think you could get away with it and that it would at least yield something interesting. It might give you a starting place for the trim of a new canopy. Just keep in mind that it would be a rough first cut.

And what does that logo panel say on the side of your canopy? I can't read it. We need to see that.

Lee


(This post was edited by RiggerLee on Oct 20, 2013, 11:09 AM)


zoobrothertom  (D 9397)

Oct 23, 2013, 2:28 PM
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"What could possibly go wrong?"

I love your company motto! Keep it up! Cool


Quagmirian  (A 110392)

Oct 24, 2013, 2:44 PM
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Thanks for the replies.

RiggerLee wrote:
And what does that logo panel say on the side of your canopy? I can't read it. We need to see that.
Nothing particularly exciting.


Attachments: canopy_logo4.png (42.2 KB)


Quagmirian  (A 110392)

Nov 3, 2013, 3:19 PM
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A little update here.

I've changed my design again. I'm going for a 210 sq ft nine cell, made from the same lovely coloured fabric I used for the brown thing.



I got some brass grommets set in my slider, but due to a misunderstanding the inner diameters are only 3/4 of an inch. Is this big enough for a canopy lined with Dacron or will I have to go with Spectra?

Also, here's a diagram which doesn't really show much but will probably convince some people that I know what I'm doing.


Attachments: 2794_194_139_small.png (27.4 KB)
  parts.png (24.5 KB)


RiggerLee

Nov 3, 2013, 7:36 PM
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That's going to take a little more explanation.

Where exactly are you getting that drawing from?

Where are you getting the glide angle from? Measurement on the last canopy?

Trim the same as the last canopy?

Are you assuming the suspention point from your java foil and what aoa are you assuming?

And then what? you're going to the aoa of the wing as a whole at center point?

I'm just not sure I understand your design path.

And what aoa are you predicting? It looks pretty high from that drawing. Looks rather flat trimmed.

If that is the aoa that you are expecting relative to the center cell of the wing I'd incurage you to try doing a rotation around a line parallel to your glide slope through the y of the riser. If you think you've got a grasp of the aoa and glide of the canopy then that's what the spread sheet I sent you should give you. Right now looking at your panels It looks like you are rotating it parallel to your bottom skin and I think you'll find that that is equivalent to putting a twist in the wing. It wants to twist the corners nose down and you might see some end cell closure or roll under of the top skin from that.

Lee


Quagmirian  (A 110392)

Nov 4, 2013, 2:09 AM
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Quote:
That's going to take a little more explanation.

Where exactly are you getting that drawing from?
I drew it myself in PS. I used my new trim and I have also wrongly assumed that each line will be evenly tensioned. Is there any way I can improve this?

Quote:
Where are you getting the glide angle from? Measurement on the last canopy?
The glide angle really is just a guess based on my current brown thing. I'm assuming in increase of glide from 2.5 to 3.5, based on a thinner airfoil, higher a/r etc.

Quote:
Trim the same as the last canopy?
The trim is also just a guess from the last canopy. That was based on the Pd 7 cell and then flattened. This trim is based on a flattened PD 9 cell.

Quote:
Are you assuming the suspention point from your java foil and what aoa are you assuming?
I'm assuming that the suspension point will be at the 25% chord point.

Quote:
And then what? you're going to the aoa of the wing as a whole at center point?

I'm just not sure I understand your design path.

And what aoa are you predicting? It looks pretty high from that drawing. Looks rather flat trimmed.
The aoa in full flight looks to be about 11 degrees, which makes it pretty flat trimmed. I do prefer flat canopies though.

Quote:
If that is the aoa that you are expecting relative to the center cell of the wing I'd incurage you to try doing a rotation around a line parallel to your glide slope through the y of the riser. If you think you've got a grasp of the aoa and glide of the canopy then that's what the spread sheet I sent you should give you. Right now looking at your panels It looks like you are rotating it parallel to your bottom skin and I think you'll find that that is equivalent to putting a twist in the wing. It wants to twist the corners nose down and you might see some end cell closure or roll under of the top skin from that.
So this will just generally improve performance in all areas then? It sounds like a good idea and I can see where you are coming from.


RiggerLee

Nov 4, 2013, 3:46 AM
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The lines are certainly not evenly tensioned. The lines are supporting the load on the canopy. The load cord wise on the canopy is dependent on the air flow. The java foil program is a classic two dimensional model where they break it down into a bunch of little panels along the surface with 0 flow across that boundary. You can look at a lot of things with this but what is most relivent here is that it can give you a pressure disrtobution in the flow around the wing at the surface. And it should be fairly accerat in that regard. So the the summation of this pressure around the top and bottom of the wing gives you lift, drag, and moment numbers for the airfoil but remember these are numbers for two dimentional flow around the airfoil. Lift should be pretty good, drag will probable be a bit lower then reality, and the moment or location of the center of pressure should be about right.

So for that local AoA the canopy will try to center it self so that you hang beneath the center of pressure. With a positive camber I'll take a guess that it will probable be some where around .3 cord or a bit higher. Often they will talk about forces around the AC or the .25 cord point. But this also includes a moment function around the AC in relation to the angle of attack. This is a way of looking at the movement of the CP as the AOA changes. You might find it easier to just plot the CP relative to AOA.

As to the tension on each line. If you were really interested you could intergrate the pressure along each section of the wing top and bottom and look at the forces on each line. In theory it will affect the movement of the cascades as the AoA changes. but it's probable not worth worrying about at this point. I'd just think of it as being geometricly riged and fixed and look at the pitching as a whole and not worry about what are basically aeroelastic issues. There are actually a lot of interesting questions there about how each section would like to try to shift to it's own AoA and how the inflation of the wing would like to bow the plane form but I would ignore all of that now.

Any increase in AR will improve your performance. I'm not sure where you are getting a change of 2.5 to 3.5 from. There are some basic rule of thumbs for the fudge factor used in the inducided drag equations. a rectangular untwisted wing is a standard example that they will give numbers for if only to show it's inefficentcy. They may even show graphs and data all the way down into the AR you are at. But most people don't build things that low and you may find that it's not that accerate and is just an extension of the graph to give students an idea of why you should never build a wing that short. The next step up would be to look at some form of lifting line theory. You might be able to find some code for a program that will do that for you. As I recall the restaned case of a tapered twisted wing was not too bad. But at these low AR's I wouldn't put too much trust into it till I kited it or flew it.

There is a long tradition of steeling other peoples designs as a starting point. A PD 9 cell is a good place to start. It wasn't all that steep of a trim so I wouldn't flatten it too much right off the bat. I also like flat trimmed canopies.

The suspention point will probable be farther back. I would guess .3 or more depending on the local AOA. Remember positive camber. Java should give you a good guess at the location of the CP at various AoA.

11 deg? Relitive to the zero lift line predicted by java foil? That seems a bit high to me but ok. If that's the case, given that AOA I'd use that in the rotation to create the panel set to try to set the canopy up for a constant angle of attack spanwise relative to the free stream. This means it will be a bit more like a section of a cone. The bottom skin panels will be a trapezoid, wider at the front. The top will have even more shape. I think this will let your canopy inflate more fully. If you're at that high of an AOA right now then your canopy is actually distorted slightly. It might be why you are seeing issues at diffent break settings at your end cells.

A constant AOA on a rectangular wing is not the most efficient thing in the world. The lift distribution span wise is far from a elliptical. But I would incurage you to try to keep a positive AOA all the way out to the end cells. When the canopy pitches you don't want the out side to lose lift. As I see it incorrect panel shape distorts the plane form. It kind of bends the canopy as it tryes to form it self to the surface/angle it wants to fly at. The airflow is hitting the end cell at an angle wanting to colaps it and roll the top skin under. The most extreame example would be your old "White Thing" with all rectangular panels. Remember how it just wouldn't let the top skin of the canopy open up and catch air at the end cells?

When I go back and read this these things always seem really confusing but I just don't know how to explane it any better. Or maybe I'm just full of it. Go sew some thing an see if it fucking flys. Honestly I think that's what every one else did although they will never admit to it.

Spellings going to suck on this one. If I hit preview post before I try to use their spell checker the little red underlines disappear. Ever notice that?

Lee


Quagmirian  (A 110392)

Nov 6, 2013, 8:53 AM
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Re: [RiggerLee] My little project [In reply to] Can't Post

I think, at last, I'm beginning to understand what you're talking about. Generating panel shapes is not just about making the top skins wider due to the anhedral, it's actually about trying to compensate for the reduced angle of attack towards the wingtips, if I understand correctly.

I had to consider a donut shaped ram air canopy to understand this. Unless you put some twisting in the wing, it will not have an equal angle of attack over the whole wing. A normal canopy is only about a quarter of this donut but I think the same rules apply. If I have it correct, I can now see why rotating the rib about the angle of glide produces a better canopy.

As you say, this will make the bottom skins trapezoids which are wider towards the leading edge, right?



In other news I have managed to get my local library to find some copies of Poynter's manuals. It'll cost me a bit to get them out but I'll no doubt have a lot of questions answered.
Attachments: rib_rotated_small2.png (39.0 KB)


RiggerLee

Nov 6, 2013, 10:34 AM
Post #161 of 243 (2385 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

You've basically got it. The donut is a good analogy but I'm not doing a very good job of explaining what happens at the corners.

With the "donut" you can see that all the ribs are parallel to the free stream. By that I mean that the free stream is hitting them head on at their angle of attack.

If the bottom panels are rectangular then the outer ribs are not parallel to the free stream. They are actually being hit by it at an angle. A cross wind. It's actually trying to push in on and collapse the end cell. Take it to the extreme. Imagine that the bottom skin is a trapezoid with the FRONT narrower then the back by quite a bit. See how the ribs would be at an angle and the wind would be hitting the out side of the end cell.

I think you want each cell to be facing head on into the wind. You want your canopy to be a section of that "donut".

Now that's the angle relative to the free stream. The actual truth is that the local AOA at each point on the wing is different from that. That's what induced drag is. The local AOA tilting the lift vector backwards creating induced drag. That's where the lifting line/vortex lattice stuff comes in. But don't worry about that. That's just a question of the efficiency. If you want to make it fly better change the plane form to some thing more elliptical. Don't try to twist the wing. Every thing I've been talking about here is for a steady state. When you then look at how the canopy behaves when it pitches forward or back you'll find that the AOA at the center of the canopy changes more then the end cells. That's why I say that you could look at a... perturbed angle of attack as a twisted wing. As you examine that over a range of AOA you could then start to look at things like pitch stiffness of the canopy and some of the dynamics. I've never sat down and tried to do a model like that but it might be fun to try. But honestly the real answer is just to build something and jump the son of a bitch.

The spread sheet should start to make more since now. It's been a while but as I recall you can set the AOA and line length just like in your last drawing and that creates the panel shapes for you. You can enter an expected glide but that's really just about trying to generate numbers for a line set. Or best of my memory. It's kind of screwy but If you think you know your AOA that's all it really needs to draw the pattern. And when you're ready it will do this for an elliptical plane form. It kind of unrolls all the little triangles of the panel of the wing out on to a flat pattern. It's sort of a fractal integration.

Lee


Quagmirian  (A 110392)

Nov 7, 2013, 5:31 AM
Post #162 of 243 (2301 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

I think I have it. Here's what my panels look like without seam allowance. So is this twisting thing a good idea or not? Obviously it's only going to be perfect for one angle of attack, but it's better than having no twist at all, right?


Attachments: parts3a.png (23.7 KB)


RiggerLee

Nov 7, 2013, 6:27 AM
Post #163 of 243 (2283 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

A design can only be optimized for one condition. Full flight along it's glide seems to me to be as good a choice as any.

We keep using the word twist. I'm not sure that's the right term. The line set and trim is consistent across the canopy. It's more about keeping the whole span of the wing head on into the free stream wind. You might think of it as avoiding a side slip of the end cells into the relative wind. That's an awkward way of saying it. Basically I'm advocating building the plane form so that you have a consistent angle of incidence of the wing with the local section of the wing facing head on into the local free stream flow.

Don't confuse that with the local AOA at each section which you might be able to determine with a little analysis. And when I talk about examining the wing at other angles of attack it would involve looking at the local angle of incidence when the canopy pitches. That change will not be constant along the span. When I say you might be able to treat it as a twisted wing in that case I'm saying that you might be able to use a constant spanwise twist in a wing model to approximate the change in AOI along the wing. This is not exactly correct but I'm saying that because it's a relatively solvable design that an open source peace of code could deal with. If I could find my old flight dynamics book I'd look up the one we did in class.

At this point I'd start drawing patterns and cutting fabric.

As a next step you might start looking at the aero elastic issues. For example the distortion in the wing from the inflation of the half cells. In theory if the pressure all around it were consistent the distortion in the top and bottom panels would be a function of the width and the height of the cell. Taller the cell the less arc in the skins. As you move towards the back of the canopy the rib becomes thinner, the ratio changes and the angle of the arc of the top and bottom skins increases. You could start to include this in your patterns. Note that this will trend opposite to the changes you are making right now. On the other hand ignoring this may create a certain amount of tension across the tail of the canopy and actually help to flatten the back of the cell. You might also have to look very closely at the flow around the end cell to really get an idea of the span wise pressure and tension in the canopy to give you a good idea of the distortion. That would actually be a very difficult problem to look at in detail. And I'm not sure it would give you a better canopy. Again with the just build it theory of design.

Lee


Quagmirian  (A 110392)

Nov 10, 2013, 5:32 AM
Post #164 of 243 (2169 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

Just when I think I understand what's going on, I'm reminded that I know nothing in the grand scheme of things. Oh well, at least I'm making an effort.

How about this then. A 'twisted' topskin with more width towards the nose, allowing the end cells to open up properly, and a rectangular bottom skin, to counter the effects of ovalisation towards the tail.


Attachments: parts4.png (23.6 KB)


RiggerLee

Nov 10, 2013, 10:37 AM
Post #165 of 243 (2137 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

I think what you're describing would be... odd. I may be just confusing the hell out of you with shit which although theoretically interesting to me is of no practical interest to you. But I'll take a shot at it. What you're basically saying there is that the change in span of the half cell, or more specifically the increase in that span for the arc of the inflation, is directly proportional to the thickness of the rib. Which is not true. In fact the rib is not a perfect wedge although the tail is close to that. The real answer would be tougher. Let's say that the out wards tension in the skin is equal to the height of the rib. What this basically says is that the pressure on the out side of the rib at the end cell is equal to the pressure on the top skin at that point. See the problem already? But bear with me. So what I'm going to say is that the angle of the top skin where it meets the rib is no longer 90 deg but "theta". I'm going to say that the ribs are still at there same places in space but stretch the top skin half cell "s" to make an arc "a" that will meet the rib at angle theta. I'm going to say that theta is a product of the forces pushing out on the top skin and out on the rib so a ratio of the half span of the cell and half span of the rib thickness. Remember there is the bottom skin doing the same on the bottom half of the rib. I'll ignore the fairly significant fact that there is less pressure differential on the bottom side for now but this really should be included. I suppose you could look at it as a ratio of the top and bottom skin pressure coefficients. Setting that aside I just want to show you how the math might work.

theta=pi/2-atan(t/2s)

"r" the radius of the arc

r=s/2sin(theta)

a=2r*theta

In truth the cell should be made from two peace's of fabric seamed together at the unloaded rib but here we are pushing all of this change to the out side edge of the cell. Then what about the trailing edge? in truth you should narrow it back down substantially to the original width. Maybe looking at the sagitta of the arc decreasing it down at the rate of a curve down to zero at the tail. Are you getting the idea that it's not a straight triangle that you're subtracting to balance the very real trapezoidal shape of the bottom skin panel? And this really isn't a fair assessment. I'm fudging hard on some of those assumptions. In truth I think you would have to look at the actual flow around the end cell, remember that there is a big ass tip vortex there, and look at the Cp along the cord top and bottom at that point. And even that is different for each cell do to the local AoA which varies from induced drag. You might also look at the way the different cells want to surge in front or lag behind as the each try to reach for there natural glide angle based on there trim to compensate for the local AOA created by the induced drag. That in it self wants to... bend the wing for or back just like the inflation wants to bend it back. Let me think... I think you'll find that it actually wants to bow the outer ends of the canopy forwards. I say that based on what I recall of the span wise lift of an untwisted rectangular wing which is far from an elliptical. So there you have something fighting the "inflation".

Is that confusing enough? That's what you get for asking me questions and making me think about shit. Personally I'd disregard all of this. As you probable should do with most of what I say. Here is my recommendation which is worth exactly as much as I'm charging you for it. IGNORE AERO ELASTIC ISSUES IN THIS ITTERATION OF YOUR DESIGN. I would build it as a rotation around the free stream line as we discussed which will give you a trapezoidal bottom skin panel and fuller top. What I think you should do on this canopy is establish you're construction techniques. What I mean by that is freeze your seams design. Go and find a real double needle sewing machine. Get a folders for your seams. How ever you're going to do them. Learn to sew and build it right. If you set this up properly it will cut the construction time down to a fraction of what it took you to build the last canopy.

You're on a good track. There is nothing wrong with you're designs. They are very conservative. They are flying fine. I would not expect major issues. I think it's time to get serious about the other half of the equation and work on being able to actually build them.

And for gods sake when I start wondering off on a tangent like these distortion issues just ignore me and go sew some thing. It's all straight out of my ass any way.

Lee


Quagmirian  (A 110392)

Nov 14, 2013, 11:00 AM
Post #166 of 243 (2009 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

I can't quite build an entire canopy at the moment due to a lack of that money stuff. However, I have managed to get a couple of copies of Poynter's manuals from the library, which I am certainly not scanning into my computer for later reference. I haven't read them from cover to cover yet, but there are a few things that have caught my eye.

Volume_2_page_325 wrote:
"In flight, the span of the ram air canopy is often shorter at the leading edge than at the trailing edge due to cell inflation"
Have I got this wrong, or is this the reverse of what you were saying about aeroelastic issues, RiggerLee?


RiggerLee

Nov 14, 2013, 11:16 AM
Post #167 of 243 (1997 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

That seem backwards to me. At least in terms of inflation. What you may be seeing is that the unloaded ribs will shift upwards. This also narrows the canopy. As the canopy slows if flare for example this will exaggerate. I'd say the distortion is a balance between inflation pressure and lift at that point of the cord which would cause more of this type of distortion at front and perticurly at low air speeds. Also if you pull down on the tail you squeeze the air out of the tail of the canopy which means the tail is able to fully expand span wise. This explains why the canopy looks so pinched, narrow at the front when you flare and land. You're out of airspeed and inflation. So At the point when you need all of the area it's actually at it's worst.

Lee


Mac  (C 101464)

Nov 17, 2013, 9:30 AM
Post #168 of 243 (1862 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

This thread is outstanding...this is extremely impressive... (From an effort, focus, and passion point of view)...

Sorry for the added noise, just had to doth my cap to you.


Quagmirian  (A 110392)

Nov 30, 2013, 10:36 AM
Post #169 of 243 (1642 views)
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Re: [Mac] My little project [In reply to] Can't Post

Thank you. If you like, you can jump the canopy when it is made.

Here's a technical looking image which should hopefully make it look like I know what I'm doing, even though I have no idea.



I think I've also decided on a name for this range of canopies, based on a similar looking older canopy. I don't think there'll be any confusion.



In terms of where I go from here, I'm still faffing with some design details and what sort of seams I will use, but as soon as I can find somewhere to work I will begin production.
Attachments: 2740_194_150_stab_new_tilted_small.png (54.1 KB)
  logo_idea2.png (36.4 KB)


JerryBaumchen  (D 1543)

Nov 30, 2013, 3:33 PM
Post #170 of 243 (1606 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Hi Quag,

Quote:
I have no idea.

Welcome to the club. Tongue

Are you going to have the outer lines attach to the stabilizer?

That is how it looks to me.

If so, that would put the inner A-lines farther forward that the outer A-lines during packing & in-flight.

JerryBaumchen


mark  (D 6108)

Nov 30, 2013, 5:20 PM
Post #171 of 243 (1583 views)
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Re: [JerryBaumchen] My little project [In reply to] Can't Post

JerryBaumchen wrote:
Are you going to have the outer lines attach to the stabilizer?

That is how it looks to me.

If so, that would put the inner A-lines farther forward that the outer A-lines during packing & in-flight.

I think you may be mistaking the chord line for the seam between rib and stabilizer.

Mark


JerryBaumchen  (D 1543)

Nov 30, 2013, 10:25 PM
Post #172 of 243 (1563 views)
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Re: [mark] My little project [In reply to] Can't Post

Hi Mark,

And I think you are correct.

Unsure

JerryBaumchen


Quagmirian  (A 110392)

Dec 8, 2013, 8:40 AM
Post #173 of 243 (1381 views)
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Re: [JerryBaumchen] My little project [In reply to] Can't Post

Yeah, as I said, it's supposed to look technical and confusing without really showing anything. Wink

On the subject of panel shape, I can't help but notice that accuracy canopies often have a trapezoidal looking planform. Is this intentional or some unwanted side effect?

Image taken from PD's facebook page.



Also, I finally found out what the 'STAB SLK' dimensions are on PD trim charts, and I have modified my stabiliser drawing appropriately.


Attachments: pd_cropped_sized.jpg (51.8 KB)
  stab_slack.png (29.9 KB)


RiggerLee

Dec 8, 2013, 9:30 AM
Post #174 of 243 (1369 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

That canopy is not trapezoidal. What you're seeing is the distortion caused mainly by the unloaded ribs floating upwards when you are at very low air speed with low dynamic pressure trying to inflate the canopy. The tail is spread wide because by pulling down on it you squeeze all the air out of it, flattening it to it's actual width. Also there is more lift at the front of the canopy trying to distort it fighting against the limited inflation of the canopy trying to spread it. So span wise shrinkage is at it's worst.

Lee


Quagmirian  (A 110392)

Jan 14, 2014, 1:53 AM
Post #175 of 243 (1034 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

I have a new rib design... again. This one's for a 7 cell. I have turned to the dark side and introduced a nose lip.



Here's where I am with the project right now. I'm saving up a bit of money so that I can buy proper materials, but one thing I don't have is anywhere to build my new canopy. Sure, I can do the sewing on my home machine in my bedroom, but I don't have anywhere to cut out the pieces. I could really do with a rigging loft of something similar.

Also, does anyone know what crossports are actually for?
Attachments: new_rib_small.png (14.2 KB)


Blis  (Student)

Jan 14, 2014, 4:47 AM
Post #176 of 243 (2567 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

I would imagine that they're there to make sure that canopy inflates evenly...


RiggerLee

Jan 14, 2014, 10:08 AM
Post #177 of 243 (2475 views)
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Re: [Blis] My little project [In reply to] Can't Post

What are they for really? I think I can tell you the general philosophy but the truth is that perfectly good canopies have been built both with and with out them. And although most people have felt that they are a good idea they have at times caused problems.

So it goes like this. The classic thought is that you need them to help equalize the pressure between cells. It helps to fill the cells on opening inflating the whole canopy smoother helping to avoid things like end cell closure and off heading openings. Let's say on a good opening that the center cell opens first and starts to surge forwards and basically runs over the end cells leaving them behind un inflated. The front of the end cell is basically tucked under and not catching air. This is not uncommon. In theory the cross flow during opening would help to avoid this and would help to pop open the end cells after opening. It can be harder to get into deep enough breaks to get it to pop out and open with out them.

That was the conventional thinking. The truth is that there have been canopies built with out cross ports. For instance, Charter wound up buying this odd nine cell zp canopy in his first rig. It was an odd thing, I think it came out of south Africa. Damn, I'm brain locking, can't remember the name. It was the only one I'd ever seen. He got it cheep because no one had ever heard of it and Dallas is kind of snobbish about it's PD and Icarus canopies. It was kind of saber/stilettoish. It turned out to be a really nice canopy for him. He jumped the shit out of it. No cross ports. I seem to recall that the Strong Set 400's did not have cross ports. Maybe some one can confirm that? My memory is going. There are probable others but those are two that come to mind. It seems to be some thing that was tried when people were switching from F-111 to zp. It might have been an attempt to control the openings by slowing the inflation of the canopies by reducing the filling through the cross ports. I don't know that's just a guess. But the canopies seem to open and fly fine with out them. Or at least well enough. For example the I've seen the set roll tips under and it's not really prone to popping out on it's own with out help.

Problems. I told you about what was believed to be a cross flow issue on the early FX canopies. The angle of attack and pressure is not the same across the nose of the canopy especially in a turn. So there can be cross flow through the canopy. The flow on one side is no longer stagnant. You can create a dimple and start to cave in one side of the nose on a large lip or baffle that closes off the majority of the nose. Or At least that was the thinking when he was having problems at the time. So in a since the cross ports were actually making the canopy less stable. I always wondered if you could put a flapper valve over the cross ports on a couple of the ribs and get the best of both worlds. Say if you separated the canopy into groups of three cells with air lock valves so that the air could only flow outwards.

Personally I like cross ports. I've even enlarged them on some of my canopies for base. I think they would be a good thing in your design. You're a long way from a design where you might see any kind of problem. The vast majority of canopies have at least two cross ports of some type. For example some use mutable narrow vertical slits to better support the rib. Personally I think they were just having fun with their laser cutter. Look what we can do!

Lee


RiggerLee

Jan 14, 2014, 10:27 AM
Post #178 of 243 (2464 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

And if you want to put a nose lip on there I think you could come down 25% of the nose cut with no problem. It would probable help capture the airflow escaping the top of the nose at high angles of attack like on flare.

The real question you should be looking at is how you want to sew things. For example how are you going to sew the lip at the leading edge of the rib? Have you done a test yet. It might be a bit awkward on the non load bearing ribs. Don't buy your self problems you don't have to have. It's time to focus on construction. A rounder edge, basically curving the top skin down rather then a sharp turn might be easier to sew then a sharp turn. Just a thought.

Have you talked to the sewing machine shop yet? You're at a point where construction may start to dictate design. And there's nothing wrong with that. One is not more important then the other.

Lee


pchapman  (D 1014)

Jan 14, 2014, 10:40 AM
Post #179 of 243 (2445 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

And there were the Atair Cobalts which either did not have crossports in the 3rd and 6th ribs in from the ends, dividing the 9 cell in thirds. (Although that is what they advertised, some apparently had very small crossports in those ribs). They were trying to promote having the center fill first, without opening up the outer wings, thus staging the opening. Opinions were rather mixed whether they achieved that or not!

Yet cross ports were enthusiastically adopted by early squares, after beginning without them. It must have helped to fill those end cells, particularly on opening.

Some canopies (which? how many?) don't bother with crossports in the center rib.

I suppose if a canopy (a) opens well enough anyway for whatever reason, (b) doesn't have a tendency for the end cells to tuck (because of good design regarding angle of attack and twist in the wing), then crossports won't be really needed unless one gets into the rare situation of actually having a tip fold in. So my gut reaction about that odd South African ZP thing that RiggerLee mentioned, is that it would be perfectly fine normally ... but I'd still be more wary of it in turbulence.

Quote:
mutable narrow vertical slits
"Multiple" is what Lee meant. Yes, that does look like playing with the laser cutter input data.


indyz  (D 28525)

Jan 14, 2014, 10:43 AM
Post #180 of 243 (2439 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Quagmirian wrote:
Here's where I am with the project right now. I'm saving up a bit of money so that I can buy proper materials, but one thing I don't have is anywhere to build my new canopy. Sure, I can do the sewing on my home machine in my bedroom, but I don't have anywhere to cut out the pieces. I could really do with a rigging loft of something similar.
You can use sheets of masonite as a cutting surface. It's not ideal, and will wear out pretty quickly, but sheets are so cheap it doesn't really matter. Masonite is also nice for making patterns.


RiggerLee

Jan 14, 2014, 10:49 AM
Post #181 of 243 (2447 views)
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Re: [pchapman] My little project [In reply to] Can't Post

Actually I think the lack of cross ports in the center rib is probable more of a structural issue. There is a lot of airflow captured by the center cell of the nose on opening. I can see it stressing the rib and stating a tear there and then between the b and c you probable have the bridle attachment with all the tapes transferring the load down the rib to the bottom seam and out to the loaded ribs.

Lee


RiggerLee

Jan 14, 2014, 11:00 AM
Post #182 of 243 (2434 views)
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Re: [indyz] My little project [In reply to] Can't Post

Even just 1/8 or 1/4 inch hard board works fine. Move all the furniture out of the way and lay it out on the floor. It's hard on your back but that's what I do now that I don't have room for a proper cutting table. But make your self a little rack for your roll of fabric. Just two t shaped end peaces made from 2*6 with a notch to hold a peace of conduit for the roll to turn on. It's worth it. And even when I had a full size cutting table I often climbed all over it as I cut so I might as well have been on the floor any ways.

Here's a thought. If you could get your patterns into a real drafting program you could ask some one to cut it for you. It would also bypass the issue of finding good fabric. Call Red at flight concepts. He might do it for you. Wouldn't it be nice to just get a box in the mail with all your peace's laser cut for you?

Lee
Lee


Hellis

Jan 14, 2014, 11:47 AM
Post #183 of 243 (2407 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

I agree a canopy does not need to have crossports, but they make the opening easier.

I have a BT Pro and as long as the end cell closure is even, it's not a big issue.
But if I only get end cell closure on one side the canopy dives very steeply.

But isn't the crossport patented or something?
I have a slight memory of I heard old canopies was made without crossports but with markings where to cut because of 'some reason'.
Maybe I remember wrong or heard false stories.


Quagmirian  (A 110392)

Jan 17, 2014, 9:03 PM
Post #184 of 243 (2251 views)
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Re: [Hellis] My little project [In reply to] Can't Post

I did some more slope soaring on the moors and this time got it on camera.

http://www.youtube.com/watch?v=9Dof6XwXq5g

Also I now have a decent headset if anybody wants to talk about canopies on Skype.


Quagmirian  (A 110392)

Jan 28, 2014, 6:27 AM
Post #185 of 243 (2052 views)
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I got my huge roll of fabric delivered today, so I suppose that means I can actually start construction.







Parts less seam allowance

Attachments: stab_tech_small.png (37.1 KB)
  bottom_tech_small.png (22.2 KB)
  210_pd9_cell_slider_small.png (11.5 KB)
  parts_small.png (21.0 KB)


Quagmirian  (A 110392)

Jan 31, 2014, 4:38 PM
Post #186 of 243 (1891 views)
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RiggerLee was right, sewing nose lips is hard. Frown I'm glad I decided to get some practice first. Sorry for the terrible quality, but you just might be able to make out a non loaded top seam here.


Attachments: 1.jpg (34.3 KB)


Quagmirian  (A 110392)

Feb 6, 2014, 12:46 PM
Post #187 of 243 (1731 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Slightly better quality pictures:

http://i.imgur.com/97PQsz6.jpg

http://i.imgur.com/Eb1A91u.jpg

I popped a few drops of oil in my shitty sewing machine, played with the tension a bit and managed to get it to sew through 2 layers of type 7, 2 layers of type 8, and three layers of type 4 webbing.




(This post was edited by Quagmirian on Feb 6, 2014, 3:08 PM)
Attachments: HPIM4301small.jpg (118 KB)


Zlew  (D 21616)

Feb 6, 2014, 5:25 PM
Post #188 of 243 (1684 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

I've loved following this thread. So cool to watch your project evolve.

I'm not a rigger, and hope someone who knows better will chime in if need be...but harness sewing like that is something you don't want to fuck up. I know riggers spend big bucks on machines that can safely stitch heavy/harness webbing.

Keep posting pics.

Dont die.

:)

Z


(This post was edited by Zlew on Feb 6, 2014, 8:41 PM)


Quagmirian  (A 110392)

Feb 7, 2014, 11:02 PM
Post #189 of 243 (1590 views)
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Re: [Zlew] My little project [In reply to] Can't Post

Oh yeah, of course I'm not sewing real harnesses, I just wanted to play about with my machine.

@RiggerLee, what I have done in the past for the three centre cell ribs is to have just two crossports like this:


Should I have no crossports at all in the centre cell or will that be fine?
Attachments: centre_ribs.png (5.20 KB)


RiggerLee

Feb 7, 2014, 11:31 PM
Post #190 of 243 (1566 views)
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Give it a try. It's the section between the B and C that you'll have to sew all the tape onto to carry the load of the bridle. The front cross port is the only other question. The center cell will be wide open catching a lot of high speed air. You'll just have to see how much load you get on that fabric. Worst case you'll get a tear starting at the cross port.

It's time to build it, jump it, and see.

Have you found a sewing machine yet?

Lee


ineed2fly  (A 57696)

Feb 10, 2014, 9:00 PM
Post #191 of 243 (1410 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

I only put attachment reinforcement load tapes on the center cell, and center top and bottom skins in an I shape. I just leave out the center cross port for that section. You shouldn't need to do this for the center 3 ribs, only the very center non load bearing rib.

And for what its worth, I build all of my harnesses on my base rigs with tightly zig zagged E thread out of type 8 webbing.

Riggerlee had even mentioned something about the flexon originally being TSO'd with bar tacks instead of 5 chord. IMO zig zagged E thread is fine for harness work in lighter duty webbings like type 8, or type 7 in the case of my speedflying harnesses. If you start working with type 7, or more than 4 layers, it stops being viable. It also takes a little longer to sew than a walking foot with 5 chord likely would.


RiggerLee

Feb 10, 2014, 9:53 PM
Post #192 of 243 (1402 views)
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Flexon TSO'd with zigzag? News to me. I tend to think that it could be done if it was designed properly so that ALL loads were in shear but with most typical harness designs at least some of the loads like those on the reserve risers tend to peal the upper junction. Climbing harnesses are mostly done with zigzag but they are also prone to abrasion of that stitching and are semi disposable with limited life spans.

Lee


Quagmirian  (A 110392)

Feb 11, 2014, 2:06 AM
Post #193 of 243 (1377 views)
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@ineed2fly I thought there might be some force at the end of the reinforcing tape for the bridle on the topskin. I changed the v tapes on the loaded ribs to meet there so the force can go down the lines. Is this completely unnecessary?

@RiggerLee What do we think of this non loaded bottom seam?

http://imgur.com/a/813Tm


RiggerLee

Feb 11, 2014, 8:03 AM
Post #194 of 243 (1331 views)
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I'd try to center the tape a little more to get a better bight with that bartac. I'm not sure you need to fold it back under like that. It's esthetically attractive but I don't think it's structurally necessary. Some manufactures have stopped doing it. If you think about it the only way to sew a seam like that will be with a down turn folder actually on the foot it self. That can probable be done but it would have to be custom. So why buy your self that pain in the ass.

It's not uncommon to have the v tapes meet that top skin tape some times they even reinforce the top skin panels on ether side. They do that on some base canopies where use large pilot chutes with out bags. But the top skin is actually a bit looser then the bottom most of the load should go down the rib to the bottom skin then out to the load bearing seam.

Lee


Quagmirian  (A 110392)

Feb 12, 2014, 3:15 AM
Post #195 of 243 (1281 views)
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Here's the corner seam where the stabiliser meets the tail.

http://imgur.com/a/5tYT4

On the subject of bottom seams, I am really tempted to do what I did last time and make them flat and simple.


RiggerLee

Feb 12, 2014, 5:27 AM
Post #196 of 243 (1260 views)
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You're sewing's looking pretty good. I can't see exactly how you're doing your bottom seam. I see you're running you're stabilizer all the way to the tail. I'm honestly not sure how much you gain by that. I'm not sure how much you gain in flight and when you flare the tail will bend down quite a bit loosening it. Some people bring the stabilizer up a little sharper so the edge meets the bottom seam a little farther forwards on the cord. That way when the tail pulls down the back edge tape on the stabilizer is still relatively taunt. On the other hand the larger stabilizer kind of blooms out wards giving you a bit more surface. I guess the only way to look at it would be in a wind tunnel or maybe by kiting. I wonder if it would be noticeable in how the lift and drag change at those higher angles of attack across the control stroke. I wonder if it would even be noticeable. But this is just me rambling. It's time for you to ignore all of us and just go build a canopy.

Sewing machine. It's time for a sewing machine. Start hunting for a 112-w-116 singer or some equivalent. Worst case a 212-w-140 Singer It's actually a fine machine lighter then the 112 but it doesn't have a puller. neither of these have a reverse. If you really want something nice get like a Juki with a reverse. It's an oiler but you're going to run the hell out of it so that's a good thing.

Lee


Quagmirian  (A 110392)

Feb 12, 2014, 6:28 AM
Post #197 of 243 (1247 views)
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riggerrob wrote:
Yeah!
Whatever Riggerlee said, plus you might want to extend the stabilizers all the way to the trailing edge. Longer stabilizers will help (structurally) stabilize the rear corners (ala. Triathlon and Diablo).
RiggerLee wrote:
I see you're running you're stabilizer all the way to the tail. I'm honestly not sure how much you gain by that. I'm not sure how much you gain in flight and when you flare the tail will bend down quite a bit loosening it. Some people bring the stabilizer up a little sharper so the edge meets the bottom seam a little farther forwards on the cord. That way when the tail pulls down the back edge tape on the stabilizer is still relatively taunt. On the other hand the larger stabilizer kind of blooms out wards giving you a bit more surface. I guess the only way to look at it would be in a wind tunnel or maybe by kiting. I wonder if it would be noticeable in how the lift and drag change at those higher angles of attack across the control stroke. I wonder if it would even be noticeable.
Hmm. And yes I am looking for a new machine. Well actually, I looking to use someone's loft, that way I have all their equipment and expertise on hand.


ineed2fly  (A 57696)

Feb 13, 2014, 3:44 AM
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My bad, it was someone else, over at BJ.com

Circa 1990, Sandy Reid certified the Flexon harness sewn mostly with bar-tacks. Most of those bar-tacks were 3 inches long!
Only the Flexon shoulder joints (directly below the 3-Rings) were sewn with 5-cord.
Flexon was the first American harness with hip and chest rings and it survived all the heavy-weight and high-speed drop-tests required by FAA TSO C-23C.

The only problem was that bar-tack machines were not durable enough for sewing harnesses year-in-and-year-out. .. which is why Rigging Innovations had switched to sewing most of their harnesses with 5-cord by the time I started working there in 1994.


ineed2fly  (A 57696)

Feb 13, 2014, 3:49 AM
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Also, as far as folding the bottom of the seam like that, I do the same thing on my canopies, but only for the bottom non load bearing seam. Only reasoning being, that I have a 1cm seam allowance on the top of the ribs regardless of it being a load bearing or non load bearing seam. But the bottom load bearing seam requires a 2cm seam allowance, the bottom non load bearing seam requires a 1cm seam allowance. So I have found it easier to just fold the non load bearing bottoms over to make up for the extra length, as opposed to making a completely separate pattern for the non load bearing rib that is just 1cm shorter on the bottom.


RiggerLee

Feb 13, 2014, 4:26 AM
Post #200 of 243 (1150 views)
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This guys at the point where he needs to make those kinds of seam decisions. He's getting ready to buy his first sewing machines soon and he needs to have his construction sorted out so that he can start looking at folders for the various seams. I've given him my two cents, for what little it's worth. How do you build you're seams? What kind of folders do you use? Where did you get them? Where any of them off the shelf or are they all custom jobs. Could he perhaps reference your orders to help get them set up right. My experience is that custom folders are expensive and some times take more then one try to get them right. He's kind of hitting a wall. He's not a sewing machine guy and it's intimidating for him. He could really use a bit of help here to get him over this next hump. A double needle is a pretty big commitment for him. He needs to get it set up right so that it will really work for him.

I'd give the guy a hand but he's on the wrong side of the ocean. I don't suppose there is any one local that could hold his hand through this? Come on you remember what it was like trying to buy your first industrial machine.

Lee


Quagmirian  (A 110392)

Feb 13, 2014, 10:45 AM
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As it happens, I have found someone relatively local who will let me use their facilities. I know in the long term I will need my own machines etc, but for now I just need someone to show me the ropes and fill me in with some rigging knowledge and experience.


ineed2fly  (A 57696)

Feb 13, 2014, 9:41 PM
Post #202 of 243 (2145 views)
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I build my canopies without folders. I just pin the fabric together at the reference marks on the top skins. And for the bottom seam I just pin the A B C and D, and fold by hand as I go. I really don't think I would be all that much more efficient with a folder, especially switching from one folder to the other etc. I have no plans to buy folders in the foreseeable future.

Last time I was in the badseed loft, his technicians were all building canopies without folders as well.


RiggerLee

Feb 13, 2014, 11:15 PM
Post #203 of 243 (2124 views)
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Hmmm. I guess I think a little differently. How many employs have you had? There are a couple of things that can really get you into the mind set of automation. The first is building big batches of things by your self. It really teaches you to break production down into stages where all the task are done together at one station or one configuration. The second is employees. It teaches you how to make things stupid. Stupid as in unskilled, thoughtless, automated. Folders are a part of that. If you can train them to use the folder, that's a big if, it's your best bet to get the consistence you need from an employ. And even doing it your self it can speed your own work once you become proficient with their use. As an example I love my lap seamer. And it's not a big deal to set some of these up. As an example the lap seamer is just on a front plate. The plane one slides out and the folder slides in, done. A tape foot in not in the way most of the time and I often just leave it on the 1/4 gauge. Same thing with the roll holder, doesn't bug me. The puller on the 116 is a bit of an annoyance some times but I can still do 90% of the things I would do with that machine. If it's annoying then I'll drop a straight head into one of the other tables.

What I'm basically saying is that they are tools. You can do a job with out the right tool but it's so much easier if you're set up right. If you're doing enough of one thing, and main seaming a canopy falls in that category, then I think a good folder can be worth it's weight in gold. And they cost about that much.

Lee


ineed2fly  (A 57696)

Feb 14, 2014, 6:26 AM
Post #204 of 243 (2072 views)
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Well, I don't fold my top seams over on my non load bearing ribs, I just do a 1cm raw finish seam. For the bottom non load bearing seam and I just fold it in half, but its all along the block of the fabric so its easy sewing once you get it started. For the top non load bearing seams, I do a 1cm raw finish seam, and i just make 2 passes on a single needle. And for the bottom load bearing seam, I just hold like 20" away from the foot, and fold it as I go. The only seam that I think would really be any faster would be the top load bearing seam.


RiggerLee

Feb 14, 2014, 6:50 AM
Post #205 of 243 (2058 views)
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Two passes with a single needle? Dude you got to get a double. Not just because it's a singe pass but sewing it twice like that will tend to increase your shrinkage. Not to mention the esthetic issue of spacing. Do you have any pullers? That would also cut down on your shrinkage. It would make your sewing more consistent. And it frees up your hands to focas on the fabric in front of the machine. You'll sew better and much faster.

What about your loaded bottom seam? Are you doing it like a PD seam. I honestly don't know exactly how they do it in shop but I would set up a double up turn and single down turn folder. And what about all the little prep steps. Got to have a tape foot with a puller. If your doing that by hand you'll go insane. Use a tape foot once and you'll never, ever go back. How about a upturn on the bottom plate for all the edge tapes you're going to do. Just run it through along with your tape foot and puller and you'll have all your prep done in less then 1/4 of the time it would take you by hand. Tail, how you building it? A full roll for the tail could make that a whole lot easier to sew. And a bar tack goes with out saying. Automatic machines are a god send.

Lee


Quagmirian  (A 110392)

Feb 14, 2014, 7:49 AM
Post #206 of 243 (2047 views)
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I think when you have automatic bar tackers and a machine for every task you stop being a home builder and start becoming a factory. About the loft I'm planning to use, there aren't any puller or folders but there are double needles which is a step up from what I'm used to. This also means I can go with neater seams as well. I'm thinking something like Nick's construction method should work well. And yes, I am going to modify my design slightly so that the rib lines up a bit better with the bottom skin.


RiggerLee

Feb 14, 2014, 8:00 AM
Post #207 of 243 (2043 views)
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Yah!! factory. Now that's what I'm talking about. And actually all the things I just listed to that guy could be done on one double needle sewing machine. Then go and barrow time on some bodies bar tack to finish up. But once you use a bar tack it will be your next perches.

Lee


Quagmirian  (A 110392)

Feb 16, 2014, 9:33 AM
Post #208 of 243 (1967 views)
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Not really related, but my old container may have been attacked with a stitch ripper. Maybe it's losing weight and turning into a ground launching harness, maybe it's turning into a future rigging project, who knows.


Attachments: HPIM43382.jpg (817 KB)


monkycndo  (D License)

Feb 16, 2014, 9:36 PM
Post #209 of 243 (1905 views)
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Be careful, them seam rippers are dangerous.Shocked


Quagmirian  (A 110392)

Feb 20, 2014, 8:29 AM
Post #210 of 243 (1763 views)
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Yeah, I've stabbed myself once already. If anybody wants to know, I managed to separate out the harness, backpad, main and reserve containers without destroying anything. I now have lighter ground launching harness I suppose.

Good news is that I managed to source some slider tape, so I made my new slider. Bad news is that the thread tension is really fShockedShockedd up and I may just take it apart and try again on a proper machine.





Also got some 800 lb Dacron for the brake lines, so I had a little practice and measured shrinkage for the first time.


Attachments: HPIM4342small.jpg (576 KB)
  HPIM4347small.jpg (594 KB)
  HPIM4340small.jpg (712 KB)


RiggerLee

Feb 20, 2014, 9:12 AM
Post #211 of 243 (1740 views)
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It's hard to see the stitching on the slider. It may not be pretty but I'm sure it's fine. Worst case, you might break the thread on one side when it tries to stretch. Remember you may wind up changing the size any way. Odds are this wont be the final slider that you wind up with. So just go jump it and see where you are at before you rebuild it. On a separate note it looks like the tape is a little short. Like it doesn't go all the way to edge where it over laps at the corner. Personally I leave it long and fold it under a good ways at the end so that the grommet is going through at least 4 layers of that tape. Furthermore you'll often see a peace of type four webbing included at the corner. It's really just to give the grommet some thing good and solid to bight into. Then sew all that shit together to give you a good solid corner for the grommet. There's a decent bit of load there but the main thing is the grommet needs something that it can really grab to transfer that load into. It's not that the tape isn't strong enough you just need to transfer the load into it. And yes I have seen those corners tear out but it was like a brutally hard line dump. Or at least that's my theory. It could have been a brutal opening caused by the failure but I favor the former.

Lines look good. 800 is a bit heavy for most of the suspension lines but if it was cheep then go with what you got.

Lee


Quagmirian  (A 110392)

Feb 20, 2014, 3:10 PM
Post #212 of 243 (1697 views)
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The stitching on the slider is really shit in some places. As in the thread loops under the material. Upper thread tension too low? I think my tensioner's broken, lol. I know sliders are relatively easy to modify/cut holes in/replace entirely etc so I won't lose sleep over it. To clarify, the tape does go all the way to edge and folds over but in some places there's fabric on top so it looks like it's too short. I've had my inklings about extra reinforcement at the corners but I didn't know for sure. On the subject of grommets, are plain grommets and washers acceptable at all for sliders? The 800 lb line was relatively cheap at 0.70/metre and I've used it to make the lower steering lines. The main suspension and upper steering lines will be 600 lb Dacron.

You mentioned earlier something about seams not lining up correctly, where should they line up? As in where does the rib meet the panel? On the load bearing stitch row (what I've been doing), on the second stitch row etc?

Diagram may help or just confuse more.



(This post was edited by Quagmirian on Feb 20, 2014, 3:11 PM)
Attachments: bottom_seam_non_loaded.png (9.55 KB)


indyz  (D 28525)

Feb 20, 2014, 3:37 PM
Post #213 of 243 (1686 views)
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Could be low top thread tension, could be high bottom thread tension. Have you tried a fresh bobbin and re-threading the top thread?


RiggerLee

Feb 20, 2014, 4:08 PM
Post #214 of 243 (1679 views)
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You really want a good roll rim spur tooth grommet. A good grommet will have a washer with two rows of aggressive teeth on both the inner and outer edge that lock into the fabric. It's not just a ring in the hole of fabric. You are not pulling on the out side of the hole. You are pulling on the inside of the hole. The grommet should be one with the fabric, locked in all the way around. What you're setting it in needs to be heavy enough to permit this and to transfer the load to the structure. So you need some sewing around it. Enough to insure that all of the layers that the grommet is set in then distribute that load outwards to the tape of the slider. I know that's kind of long winded but it can be important. I've seen a lot of grommets miss used because people don't seem to understand this.

The proper way for the seams to meet is how ever you choose to sew them together. If it was me I would split the difference on the load bearing stitch line. In other words I would center the panel tape in the middle of the wider diagonal tape on the rib. You're bar tack is going to be as wide as the panel tape. You might as well arrange it so that that is centered on the tape from the rib. And it gives you as much leeway as possible in case you're sewing is... imperfect. Wait until you get a slave working for you. You'll need a little leeway in your construction.

Speaking of which, once you get a good sewing machine or two you need to start thinking about where you can acquire slaves. I don't know much about the cultural issues in England. Manufacturers here have gone in a number of ways. Asians are always a good bet. But they have to be old school, preferable immigrants. If they are too... integrated? into the country then they aren't really Asians any more. If they are fluid in you're English then you probable don't want them. You need some one fresher. Another possibility is LOL's. It stands for Little Old Ladies. Oddly enough they are some of the best sewers and workers. They do have their own issues. Bathroom facilities can be an issue. Let's just say they have different standards. In any case I recommend that you look around for groups or individuals that you can exploit. The real key that you should be looking for is desperation. Older is always better then younger. Single mothers with limited job prospects are usually a good bet. You may not be there yet. And you never ever hire some one until you absolutely have to. And only if they will make you money. But you should start to keep your eye out.

Lee


RiggerLee

Feb 20, 2014, 4:11 PM
Post #215 of 243 (1678 views)
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And the thread thing. Make sure you haven't just popped out of your tension plate. If it keeps popping out check how you are running the thread through the guides before the plate. It needs a bit of tension there to keep it from popping out of the plate. May be loop around then through the hole rather then going in a zigzag through the three holes as an example.

Lee


Quagmirian  (A 110392)

Feb 20, 2014, 4:41 PM
Post #216 of 243 (1662 views)
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Yeah, I had a quick look and it may be more trivial than that. I may have been just not routing the upper thread through the tensioner at all...


riggerrob  (D 14840)

Feb 20, 2014, 5:26 PM
Post #217 of 243 (1636 views)
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Some manufacturers deliberately make the stabilizers too short, so that there is less bulk in the corner seam. That make sit easier to sew.


mkael

Feb 21, 2014, 12:46 AM
Post #218 of 243 (1567 views)
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Interesting project. Cheers mate. My respect.

I noticed on your older towing pictures you looked like the brakes were out of your hands? I find that a very bad approach. Think directional control to counter lock out situations . Also imagine the towing line breaks the canopy might shoot forward. Looks like too much tension that low. You can of course use the rear risers to get some degree of control. Also the towing car line could be a lot longer and most importantly a tension gauge should be on board. Idk if you plan to do any towing anymore but I would recommend you check out some towing manuals of the pg community and get some help. You can do towing much much safer and stress free that way imho.

Also you seem to do some ground launching off that hill. It looks like a demanding place to launch . I would recommend you use a pg harness with a back protector. If you fall out of the sky nothing is good enough but they do work most of the time. That can save you tons of grief and issues from bad starts or crappy landings one is most likely to encounter.

You could get a lower hanging point to the carabiners and get a whole new feel for the wing and tons more weight shift. (there is stuff online about old carabiners breaking after heavy use or misuse. I would get new carabiners , they are relatively affordable) . Or just wear your skydiving harness underneath

Maybe you do know these sites already.
http://www.laboratoridenvol.com/index.html
A good page about hobby pg wings and stuff
Check out paraglidingforum.com too , Very good stuff there too
You can learn tons and tons groundhanding , but the summary of pg en a certification testing is also a nice read. http://www.hgfa.asn.au/...0CEN%20PG%20Test.pdf Much stuff to think about.

I do understand pg is not something you would be primarily interested about and the wings are not parachutes. But stuff like this is very much part of it. A good place to learn tons about flying , wings, lines and the sky . Would recommend that sport


riggerrob  (D 14840)

Feb 22, 2014, 3:36 PM
Post #219 of 243 (1431 views)
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RiggerLee wrote:
... I seem to recall that the Strong Set 400's did not have cross ports. Maybe some one can confirm that? ... It might have been an attempt to control the openings by slowing the inflation of the canopies by reducing the filling through the cross ports. I don't know that's just a guess. ... For example the I've seen the SET roll tips under and it's not really prone to popping out on it's own with out help. ...

....................................................................................

Correct!
Strong builds their SET 400 and SET 366 tandem mains without cross ports. SETs open fine without cross-ports. They open slowly, sequentially (center cell first and end cells later) and comfortably without cross-ports.

Most of the problems with tips folding-under only occur after suspension lines are allowed to shrink beyond factory trim. Those Spectra (polyethelene) suspension lines shrink out of trim in as few as 400 jumps. When the outboard A lines have shrink 3 inches more than the center A lines, the end cells take forever to inflate ... often only opening after the TI has pulled the steering toggles to hip level for 8 seconds.

In the worst case scenario - when outboard A lines are allowed to shrink 5 inches more than center A lines - a fist-full of end cell fabric gets trapped in a front slider grommet. The slider tries to drag the end cell down the suspension lines. Sometimes, the slide releases the end cell when it is halfway down the lines, but sometimes the TI has to pump the brakes to release the slider.
In a worst-case deployment the slider refuses to release the slider ...

Bottom line, you can your rigger now (to replace tired lines) or you can pay him/her later (to repack the reserve with a new free-bag, handles, etc, then reline the canopy with a new drogue, risers, etc.) ....


RiggerLee

Feb 22, 2014, 4:25 PM
Post #220 of 243 (1423 views)
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Just to clarify. The A line attachments were built with the tape spread out and sewn like a wedge to distribute the load. It acted like a tapered wedge and if pulled through the grommet of the slider would lock in place. So the malls occurred when the outer A shrank more then the outer B. The lines were long enough and the cascade low enough that you could actually get differential shrinkage between the outer A line and the outer B that had the slider stop on it. If the stabilizer had ben deeper or if the A line had had a slider stop on it to prevent it from pulling through the grommet we would have had a lot less malls. The shade tree rigger solution for those working at drop zones too fucking cheap to pay for the line sets to reline their canopies was to take a old RW2 ring and whip stitch it to the out side A line. In a since It became the new slider stop now that the A line had shrunk below the B line slider stop. This falls under the heading of techniques generally referred to as "nigger rigging". Note, this is not a racial epithet but a slightly derogatory term for a field expedient repair. Although it should not be a replacement for proper maintenance it will eliminate that particular failure mode.

Lee


riggerrob  (D 14840)

Feb 22, 2014, 4:56 PM
Post #221 of 243 (1419 views)
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I prefer the term "African Engineering."
Hah!
Hah!

Seriously, sewing an extra slider stop - onto the outboard A line - is a temporary solution.
The long-term solution is to replace the entire line kit when the difference across the A lines exceeds the factory spec (3 inches).
My old boss used to grumble about all the time and money I wasted re-lining SET-400s when the (Spectra) lines still looked structurally sound. My fascist rigging standards kept the malfunction rate down to 1/1500.

After I quit, my old boss allowed lines to remain in service despite being 5 inches out of trim, then he wondered why certain rigs went un-jumped all summer?????


Quagmirian  (A 110392)

Feb 24, 2014, 5:35 PM
Post #222 of 243 (1274 views)
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I got my grommets set in my slider but they're not spurred and not size 8 like I asked for. Ho hum. But apparently "they won't fall out", so that's alright. Luckily they weren't expensive either. I think I may just take them out and get a rigger to put some proper ones in.

I still have a few more thoughts about seams at the leading edge. When I sew the topskin down onto the non loaded rib, the leading edge of the rib wants to sit perpendicular to the rest of the rib, right? This means that when I join it to the bottom skin, the leading edge of the rib is sort of twisted. Is this a problem.

Also the extra reinforcement at the leading edge. I'm worried that a bartack may not be enough, especially with how I'm lining up the pieces. How about a Para flite style tab which wraps around the entire seam and then is sewn with a dense stitch pattern?


RiggerLee

Feb 24, 2014, 5:52 PM
Post #223 of 243 (1259 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Twist, no problem.

I know what you mean by a little wrap around tab. All I can say is that we've gotten along happily with out them for the last twenty years. Don't buy you're self headaches you don't have to have. Build it. Jump it. If it breaks look for the EASIEST way to fix it. Do not design some thing that is any more difficult to build then necessary. Don't worry your little head about problems that don't exist. Has it blown up yet? Then you don't need tabs.

Lee


Quagmirian  (A 110392)

Mar 10, 2014, 4:04 AM
Post #224 of 243 (1031 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

Not much to update on but I did go to my local DZ yesterday and got the chance to look at the details on a few PD canopies. I might go back with a tape measure and a camera. And can anybody tell me whether smooth clean concrete is a suitable cutting surface for canopy fabric? Since I have nothing better to do, I got a sample of zero p fabric from the local mill and it's interesting stuff. Definitely coated fabric (nice and crackly sounding) but it's not slippery at all. I'll see if I have get some specs.


RiggerLee

Mar 10, 2014, 4:47 AM
Post #225 of 243 (1026 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

It's probable a spinnaker cloth. Para gliders and some of the old para flight canopies used fabric like that. It's very stable dimensionally but the tear strength isn't as good and it's a little touchier in terms of how you sew it. It has more of a tendency to perforate.

Lee


ChrisD  (No License)

Mar 10, 2014, 7:12 AM
Post #226 of 243 (2115 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Just my opinion but I don't think cutting on concrete is a great way to cut cloth anything. It can really dull the knife blade very quickly. Do you have a sewing shop nearby, there not very large, about 3 feet by 3 feet but they have some cutting boards with a slightly resilient surface that makes a nice surface. Any spare Masonite or plywood boards?


Also canopies get retired quite often, you might consider sending out some posts to various riggers, or here and offer to pay the post for some de-commissioned canopies to take them apart if that is something your interested in?? But be advised many people like to disable their old canopies so that they don't end up being used ever again,...like cut in half,...but I think you still could get some knowledge from them anyways??

Anyways good luck, and stay safe!!! Smile

C


highspeeddirt

Mar 10, 2014, 7:30 AM
Post #227 of 243 (2114 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

Para Flite used a proprietary fabric called SS2. it was f111 with a melamine coating


Premier rwieder  (C 32349)

Mar 12, 2014, 2:49 PM
Post #228 of 243 (1969 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

It looks like your "project" is coming along nicely! Well done, it looks great!

Best-
Richard


riggerrob  (D 14840)

Mar 13, 2014, 3:41 PM
Post #229 of 243 (1896 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

Wrapping confluence tapes around those joints will dramatically increase bulk, but add little to strength. The added strength will only help during hard openings. Openings so brutally hard that wish you were not awake. The biggest problem with confluence tapes is that they might increase the thickness of the seam that your sewing machine might break needles. Then you dodge fast-moving pieces of sharp steel!

Keep your prototypes simple.


Quagmirian  (A 110392)

Mar 19, 2014, 11:43 AM
Post #230 of 243 (1759 views)
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Re: [riggerrob] My little project [In reply to] Can't Post

Yes RiggerLee, at this stage of the game I am thinking about simplicity.

I tried to make my shitty slider collapsible but it didn't go very well. Oh well, at least they're nice and cheap to replace.






Attachments: HPIM4350_small.jpg (705 KB)
  HPIM4351_small.jpg (710 KB)
  HPIM4352_small.jpg (642 KB)


riggerrob  (D 14840)

Mar 19, 2014, 4:21 PM
Post #231 of 243 (1724 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Quagmirian wrote:
Yes RiggerLee, at this stage of the game I am thinking about simplicity.

I tried to make my shitty slider collapsible but it didn't go very well. Oh well, at least they're nice and cheap to replace.

..............................................................................

???
Not quite sure why you are apologising????
The sewing looks great.
The only limitation looks like tiny grommets, which will probably still work with the thinnest of HMA suspension lines.
The major point is that you learned most of the sewing techniques used in building sliders.


Quagmirian  (A 110392)

Mar 26, 2014, 11:45 PM
Post #232 of 243 (1599 views)
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Re: [riggerrob] My little project [In reply to] Can't Post

I don't have anything exciting to report on at the moment. I bought a 'military elliptical parachute', probably a Bluetrac, from a surplus store and that should help with my studies. I've been in contact with my local mill and they're quoting 6.55/meter ($10/yard) for first quality Zero P fabric, is that about right? On the subject of fabric quality, what are the problems and dangers associated with using seconds quality goods for canopies like I am? Assuming the strength is good and it's not too bowed, porosity seems good etc, what can go wrong?


RiggerLee

Mar 27, 2014, 12:51 AM
Post #233 of 243 (1580 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Last time I bought f-111 it was about $4.00 per yard. It's been a while since I ordered any ZP so I'm not sure what it's going for.

As to seconds. I think you just listed all of the main issues that might affect you. There can also be a lot of variation in the coating. There are all kinds of imperfections that can occur in the weave of fabric. Seconds are basically goods that had too many to pass muster. Most of these things, other then esthetics, would not affect you at all. Or you could cut around them. Bowing is probable the real problem. That's the sort of thing that could make whole sections of a roll unusable. For something like this I would go with first quality goods, but even more the that I'd sit down with your rep and talk about how much bow or skew you can really tolerate. Be ready to inspect all goods that come in to the factory and make it clear to him that you will be returning all rolls that do not pass your QC program.

Lee


Quagmirian  (A 110392)

Apr 7, 2014, 11:47 AM
Post #234 of 243 (1431 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

Not much to report on at the moment. The Bluetrac is built like a tank with heavy spanwise reinforcement, rolled seams and type 4 line attachments. The fabric also seems quite heavy as well.

I also found this interesting explanation in big air sportz's manual.


Attachments: germain.png (125 KB)


Quagmirian  (A 110392)

Apr 27, 2014, 12:07 PM
Post #235 of 243 (1297 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Still nothing exciting to report on, but I have a few things I'd like to share. I still haven't found anywhere suitable to cut out my pieces, so as something to do I've been taking apart the BT-80. I have discovered some interesting things.

  • Needle gauge is 3/16" rather than 1/4"
  • No chordwise reinforcement in the bottom seams or anywhere else
  • All inner ribs are f111 type material. What are the pros/cons of this?
  • Line attachments are type 4 tape and are partially sandwiched into the bottom seam
  • V tapes on the loaded ribs are made from 1" type 3 tape. A lot of other tandem canopies are like this too Why is this?
  • No ribs have any crossports, but we've already covered this one.
  • There was also some blue 700lb Dacron in the bag too. Who makes this?


I finally got on the blower to the industrial sewing machine guy and he immediately tried to turn me off old Singers. Instead, he's trying to flog some new Diamond double needles with electronic control (no clutch) for $2000 new or $1350 used. Is that about right? They do come complete and ready to sew.


freekflyguy  (D 11658)

Apr 27, 2014, 2:17 PM
Post #236 of 243 (1257 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Phil,

I have a Singer 660 that I could be persuaded to part with, much cheaper than what he is trying to sell you.


riggerrob  (D 14840)

Apr 28, 2014, 5:11 PM
Post #237 of 243 (1147 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

...
  • All inner ribs are f111 type material. What are the pros/cons of this?
...

......................................................................................

F-111 has the same strength as ZP fabric. Porosity is un-important in inner ribs. Remember that most other manufacturers increase geometric porosity by cutting cross-ports through inner ribs.
Higher porosity ribs (and bottom skin) make it easier to squeeze air out of canopies when you pack.


Quagmirian  (A 110392)

May 1, 2014, 11:47 AM
Post #238 of 243 (1044 views)
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Re: [RiggerLee] My little project [In reply to] Can't Post

RiggerLee wrote:
On a separate note it looks like the tape is a little short. Like it doesn't go all the way to edge where it over laps at the corner. Personally I leave it long and fold it under a good ways at the end so that the grommet is going through at least 4 layers of that tape.
...
Lee
Which by the looks of it, is exactly what PD does.



I know thus isn't exactly compelling stuff, but I am learning all the time.
Attachments: pd_slider_detail_2.png (173 KB)


mr2mk1g  (C 103449)

May 2, 2014, 5:24 AM
Post #239 of 243 (959 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

So is everyone who keeps dropping in on this thread. Wink


Quagmirian  (A 110392)

May 21, 2014, 8:15 AM
Post #240 of 243 (763 views)
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Re: [mr2mk1g] My little project [In reply to] Can't Post

It's good to know I'm not wasting DZ.com server space then.Laugh

I can't really make anything at the moment, but I should be getting in some more old gear to have a look at soon, and maybe even going to a dropzone to get current again.

What I'd like to know more about is different canopy fabrics. The samples I got from William Reed Fabrics are supposed to be the equivalent of F111 and ZP, but they just don't look or feel quite right. For example, the low po fabric loses its shine and gets all creased from handling very quickly, and the ZP isn't slick and slippery at all. Also, it is very easy to make the fibres slip in both fabrics by pulling apart with the fingers. This isn't something I can do even on older canopies I've looked at. Both fabrics also feel 'lighter' and more 'frail' than what I am used to.

Am I looking at a completely different spec here or is all this normal?


Quagmirian  (A 110392)

Jun 17, 2014, 12:18 PM
Post #241 of 243 (516 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

I bought a load of old equipment for reference, including a
Super Raven and 3 Furies. I've been having a look at them and the and I've noted a few things.

  • Very little if any tail reinforcement. I'm guessing this is a more modern thing? The Fury has a single piece on each inboard steering line, and none at all on the Raven.

  • The non-loaded seams are sort of semi rolled, I've no idea how it could have been done on a double needle.

  • The rib sections generally look more like the one below, with less curve at the nose than what I am designing. What's the reason for this?

Additionally, I just want to check a few things for my planned seams.
My plan for the bottom loaded seam is to fold up the edges manually, mainly to look nice but also for a bit of strength. Which one of these will work better?

On the top loaded seam, does the seam need to be attached to the rib itself or is it alright to be left 'loose' like this?


Thanks to everyone who's been following this, with a bit of luck I should be moved out soon and I'll be able to get a proper machine and get making something at last.Laugh
Attachments: bottom_seams.png (7.38 KB)
  ribs_compare_3.png (17.9 KB)
  top_seam.png (3.97 KB)


pchapman  (D 1014)

Jun 17, 2014, 1:01 PM
Post #242 of 243 (481 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

Quagmirian wrote:
  • The rib sections generally look more like the one below, with less curve at the nose than what I am designing. What's the reason for this?

I'm guessing designers were just conservative. Canopies were what we might call "open nosed". A big open nose worked. Canopies were big, slow, more porous, and so a large open area made sure the canopy stayed pressurized at all normal angles of attack.

Only later did "closed nose" canopies start appearing. An early example of the tendency would be the PD Sabre. The top skin was brought down a couple inches along the "diagonal" that forms the normal nose inlet, without actually changing the nose profile.

Only later did we get inlets that got smaller and more integrated into a fully rounded canopy nose -- more like those on crossbraced Icarus canopies. You still don't see noses like that on intermediate level canopies, and there's talk of how canopies with such small nose openings are poor in turbulence at low wing loadings and thus low airspeeds. (The Icarus 'diamond' nose opening may be small but in the center of the diamond has enough vertical distance that it handles whatever shift there may be of the stagnation point as angle of attack changes.)

The consensus would be that fairly large nose openings are still important for good flight characteristics.

Have a look at paragliding canopies though - they have done more with keeping nose inlets small, for a whole range of canopies and not just for the very high end market. They don't have the opening problem, but do have to deal with low wing loadings and turbulence.


(Slightly earlier than the PD Sabre with its zero-p material was the short lived PD Excalibur in F-111. There was also the Paraflite Evolution, although with a lip extending up from the bottom of the inlet, not down from the top. Paraflite even mentions a patent they licensed for it, US 4406433, but what they had on the Evolution was not the fancy curved nose system seen in the patent.)


riggerrob  (D 14840)

Jun 18, 2014, 1:34 PM
Post #243 of 243 (361 views)
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Re: [Quagmirian] My little project [In reply to] Can't Post

"... Very little if any tail reinforcement. I'm guessing this is a more modern thing? The Fury has a single piece on each inboard steering line, and none at all on the Raven. ..."

..................................................................................

The amount of tail reinforcing is a compromise between low pack volume and strength. No reinforcing tapes weight the least, but as wing-loadings and deployment speeds increase, you risk tearing the control lines off, so need to add more reinforcing tapes.
The first step is to fold 6 inches of tape into the tail seam near the control line attachment, but most manufacturers find it less labour-intensive to just run one piece of tape all the way across the tail.
The second step involves adding wider (3 or 4 inch wide) tapes near each control line (tandems).
The next step involves sewing diagonal tapes (Smart reserve).
The next step is to add short tapes running forward along the ribs.



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