Jul 11, 2012, 12:17 PM
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My little project
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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)
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'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
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)
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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. 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.
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.
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
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.
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.
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?
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.
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.
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.
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.
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.
<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!!!
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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,
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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.
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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. ....
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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.
Aug 1, 2012, 8:54 AM
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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.
Aug 1, 2012, 11:35 AM
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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.
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!
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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.
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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.
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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.
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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!
Aug 1, 2012, 2:21 PM
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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.
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?
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.
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?
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.
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.
Nov 25, 2012, 8:04 PM
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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.
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.
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.
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)
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......
And video too please!!! 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!
Dec 11, 2012, 2:34 PM
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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?
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.
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.
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.
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?
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?
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.
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.
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. 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.
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 :)
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: Pilâtre 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
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.
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.
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.
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)
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.
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.
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.
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.
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.
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.
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.
Apr 22, 2013, 3:07 PM
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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.
Is there a home-built fad going around that I am not aware of?
JerryBaumchen
If the prices of mains will keep climbing up - we will see more and more DIY
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.
Is there a home-built fad going around that I am not aware of?
JerryBaumchen
If the prices of mains will keep climbing up - we will see more and more DIY
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.
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.
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
May 6, 2013, 2:52 PM
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I took the brown thing for its first flight today, a ground launch. No pictures I'm afraid. 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. 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.
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.
...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.
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:
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.
May 21, 2013, 1:11 PM
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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.
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)
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.
parts2.jpg
canopyb.xlsx
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.
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.