0
Quagmirian

My little project

Recommended Posts

Don't know what happened their. It's like it posted a blank post when I tried to reply. Oh well.

Damn, I want to get my hands on that thing. It's hard to see what you're referring to. It's one of those things where you would have to be under it to feel it. It would be helpful if you could articulate it a bit more. I'm guessing that you're not getting more out of him then, "It feels kind of funny." Not supper helpful. Now I really want to jump that thing.

I'm just going to take some random guesses and as usual it's right out of my ass.

Break input, pitch, yaw, and roll are all tied to gather. I can see a lot of variables in how they would interact with each other and how the canopy would respond and "feel".

Pitch. When you pull on the toggles, whether it's one or two, the first thing that will happen is the canopy will pitch back. It's a weird dynamic motion and I can see a number of variables in how it pitches and how it recovers which is a dynamic oscillation. Interesting note. The Icarus guy was playing with modeling this. Small perturbation and larger dynamic movements. I think it would be hard to predict exactly how these factors will change it but some things that come to mind are line length, trim, air foil, aspect ratio, break line location. Basically every part of the canopy. how long the line are, how far your CG is below the cord affect how the canopy pitches as the body dynamically swings out in front as you break. The trim and airfoil figure into the returning force. Aspect ratio affect how the drag increases as it pitches back again feeding in to the force pulling back and pitching the canopy. Where the lines are on the tail affect how much drag you make to begin with. And that's just the obvious shit off the top of my head. What follows is guesses. Don't put much credence in it. I'm making it up.

Line length. The longer it is the bigger the motion to change pitch. Long lines will slow things down but you can also store a lot of energy in that long pendulum motion. Para gliders for example store huge amounts of energy in the swing of body under the canopy. Part of learning how to fly them is learning to control that energy. The mass of the canopy and the mass of the air inside the canopy also feed into the ability to pitch the canopy. So what does it actually do? canopies with short lines feel... like a short coupled air craft. very responsive. turns are quicker, snappier. The body returns back under the canopy more quickly. You stay more under the canopy, you don't swing out as much and it snaps back over your head faster. Don't confuse that with response. It's radical, almost like a small pits. Long lines move and respond slower and you return under the canopy slower. You store more energy in a long lined canopy. Again don't confuse that with response. A short lined canopy may snap a barrel roll but that doesn't mean that that energy is stored in the canopy. If you've done big wing overs with a para glider then you know what energy storage is. Too short and it can stall really hard, but that's also trim. Too long and the pitch can be too slow. Ex. student flares high, lets up, canopy surges, flares deep but nothing happens. It dives into the ground before the canopy can pitch back over his head to make lift.

Trim. Flat canopies pitch more. They move more easily backwards and forwards. But that's my impression. Most of the flatter canopies I've jumped have been longer lined so I may have the wrong impression. But I think steeper trimmed canopies are more locked in with a greater pitch stiffness. A lot of small high performance canopies are very steep. They are fast and radical but I don't think they actually pitch that easily. And I think people that would dispute this are confusing their responsiveness with the ability to pitch. It's probable for the best. I think they could get into a lot of trouble if they could pitch more easily. I think airfoil really fits here into the pitch stiffness of the canopy in terms of how the CP changes and the return force to the normal trim angle.

Aspect ratio. I think it feeds in to exaggerate the drag of the toggles wanting to increase the pitching of the canopy as the body swings forwards and the drag increases. I'm not sure I can say how much it's in their, all of our canopies are really low to begin with and the ones where it's higher have much longer lines so I think it's lost in every thing else. Where I think it shows up much more is with single break input and the coupling of the roll and yaw.

Break line location. Ahh here is some thing interesting. Not just because it has a big affect but because YOU CAN CHANGE IT. Of all of these things the break lines are the easiest to change. Trim/line length is the next thing you can alter but any thing else basically means building a whole new canopy. This is probable how you are going to "fix" how it feels. So what can you do with break lines? Well you can move them in and out. you can control how much of the canopy you are distorting. How much drag you are making. Where that drag is, which plays into turning the canopy. With one break input, how much of it is pitch and how much is yaw. If you move your toggle out a rib you may find that you get more turn in your turn and less pitch when you pull down on one toggle. It may be that he's feeling that he's being lifted up and back when he tries to turn. Like it's flaring and stopping when he tries to turn. And when he lets up the canopy surges and dives, rather then stopping turning and planing out. It's a subtle thing. Hard to describe. Really want to jump the damn thing. It affect other things. Like your flair and stall. If you move the toggles out it may be more prone to bow tie for example when you stall it. The out side of the canopy will fall backwards but the center will still be trying to lean forwards. This isn't a bad thing, a lot of canopies are like that. Your AR isn't real high and your airfoil is pretty thick, you may not even see that.

I'm going to guess that your fairly happy with the rest of how your canopy flies. Put tabs on the rest of your outer ribs. Start playing with moving the lines around. Try going out one rib. I think you'll find that it turns more responsively and smoother but might require a bit more control stroke. Play with your flair and stall as well. Remember your backing up so you have to re look some of those things. You don't want surprises when you go to flair for landing.

I think you're close. I think you have 90% of a good canopy their. But it's going to take some jumping and testing to iron that last 10% out. I was actually disappointed when you hadn't found any thing interesting in your first few jumps. Now I wish I could play with it.

Are you keeping records? You need to keep a written record/report on every jump. Every change. You should have a three ring binder or hard drive with a write up of every jump and the film from every jump in a file for it. And the out put of a Data recorder. Like the one at PIA I sent you the like for. No data, no testing. With out records, it's just jerking off.

Lee
Lee
[email protected]
www.velocitysportswear.com

Share this post


Link to post
Share on other sites
One of the things you'll learn is to take the jumpers feed back but don't depend on it. Most of the feedback we got during prototype testing had to be taken with a grain salt. Everyone is looking for something different in the way the canopy behaves. I didn't really see anything bad happening during any of the turns. the airfoil will have quite a bit of an influence on how a canopy turns. Are they saying it is staying in the turn a little after they let the toggle up and that is what feels weird?

Share this post


Link to post
Share on other sites
Can I say thanks for the posts Lee. I do read them, but often go away with a lot on my mind and more questions than answers. It takes time for it all to sink in. Also thanks for the pictures of your setup. It's helpful to have something to look at.

On the subject of airfoils, mine is a lot more curved at the nose than the PD foil. I wonder if this could be having effects?

Share this post


Link to post
Share on other sites
I've just bought a roll of grade 1 quality ZP (beer), and I want to share the test results that came with it. See attached.

Interestingly it doesn't start out as actually zero porosity. That explains why it feels slightly different. It doesn't have glossy, slick feeling. 0.05 cfm should be nice to pack but I'll wait and see with that. It also will be interesting to see how the permeability degrades over time.

Rather worryingly there is no spec for bias/bow or quite a few other things. I will be following this up to make sure I have a complete spec sheet, but I thought this would be worth posting.

Lovely florescent yellow colour:
[inline DSCF1341_small.jpg]

Share this post


Link to post
Share on other sites

Sorry for the lack of updates for those following.

The good news is that the grey prototype 5 canopy has been cleared for me to jump, when a certain person is happy with it. Unfortunately, this is unlikely to happen any time soon, due to the season winding down and difficulty co-ordinating with the DZ staff. I've still yet to get any jumps at all on the new orange 7 cell, due to similar problems, and arguments about whether it needs a cutaway rig (deja vu anyone?).

Forgive me for sounding frustrated, but I feel like I've hit another roadblock just as I thought things were getting somewhere.

You can read the decision at the end of page 8 of this doc:
http://www.bpa.org.uk/assets/Minutes/STC-2015-09-24-pdf.pdf

I've ordered in all my materials for the next canopy, a ZP 9 cell. Obviously I'm not going to build anything until I have plenty of jumps on the two canopies I have at the moment, because that would be silly. I've also picked up a few reference books, an introduction to paragliding and an aerodynamics manual.

Anyone feel like buying me tickets to California so I can get around all this? :)

Share this post


Link to post
Share on other sites

I thought of you the other day...

I went to a dz in Italy and took all my docs with me for registration. Within those i had a german airwortiness card for my main, which is like a reserve packing card showing periodic inspections of the main by a rigger. When i asked him (the CCI) if they needed that in Italy his reply was a snigger and "we don't do that here. You can even make yourself your own canopy and jump it if you want".

It could be of interest to you :P

Share this post


Link to post
Share on other sites
I thought my collapsible slider looked a bit silly on its own, so I made a canopy to go on it. I've ground launched it and it flies a lot like a Sabre.

[inline DSCF1444small.jpg]

[inline DSCF1445small.jpg]

I now have a nice range of canopies to try out. I'll be going to Lake Elsinore again in April if anybody wants a go on one.

[inline DSCF1447small.jpg]

Share this post


Link to post
Share on other sites
Don't leave us hanging. Tell us about this Yellow thing. Trying to read the label, ZP 210? Is it all ZP? What kind of fabric is it? Is it a silicone slippery as shit like PD? How did the seaming go? Any changes to seam design? Is it the same design or is it a new airfoil and trim? You said that it flew like a saber? One or Two? Dose this mean that you've gone with a steeper trim? I was under the impression that up to now most of your canopies were more or less based on the PD nine cell which was rather flat in comparison.

Glad to here that you're going to get to do some more testing. It's actually kind of silly to ground launch them rather then to jump them from a plane. Even with out a cutaway rig you're still better off from a plane. At least you have some kind of option and altitude to use it. Choices which don't exist off a low hill. You might point that out to some of these ass hats that you're dealing with.

Lee
Lee
[email protected]
www.velocitysportswear.com

Share this post


Link to post
Share on other sites
RiggerLee

Don't leave us hanging

Oh shit sorry.

It's like my nine cell but with ZP fabric. It's loosely based on the Sabre 1. It has narrower 3/4" line attachments, spanwise reinforcement, 725 Spectra lines, a slightly flatter trim, a nose lip and a collapsible slider, and a few other minor modifications. The seams are all the same and were a bit easier since there's less bias stretch. The fabric is difficult enough to pack but doesn't seem quite as slippery as PD's stuff. I'd guess it's about halfway between Soarcoat and Gelvenor.

I know that ground launching is dangerous but it's all I can bloody do at the moment. It raises the philosophical question, am I a parachute manufacturer if my products don't get jumped?

Share this post


Link to post
Share on other sites
When I got back into jumping, after 35years off, 2 years ago, I was disappointed to see that the rigs were still very similar to the first small piggybacks we designed and built in the mid 70's. I set out to put together an experimental rig that would probably have 98% of it discarded. If I come up with one item that becomes the norm, mission accomplished. I don't mean better colors and graphics. Sounds similar to what you are doing. Don't be contaminated by the ideas of others, but listen to them so you are not on a dead end, already traveled. The people responding to you seem to know what they are talking about. That can save you alot of time. Stay on it, it will take you longer than you think, and you will make progress in a direction that you are not even thinking about now. Good luck Jim T D-3411

Share this post


Link to post
Share on other sites
Quagmirian

I thought my collapsible slider looked a bit silly on its own, so I made a canopy to go on it. I've ground launched it and it flies a lot like a Sabre.





I now have a nice range of canopies to try out. I'll be going to Lake Elsinore again in April if anybody wants a go on one.


When in April?
You are not now, nor will you ever be, good enough to not die in this sport (Sparky)
My Life ROCKS!
How's yours doing?

Share this post


Link to post
Share on other sites
Quagmirian

From the 7th for 4 weeks. Will you be there?

haha I fly out on the 8th, so liekly not :) Probably be in LA for the last 2 days:)
You are not now, nor will you ever be, good enough to not die in this sport (Sparky)
My Life ROCKS!
How's yours doing?

Share this post


Link to post
Share on other sites
Bad news from the BPA. I really was expecting that when I started I would be taken for an idiot, and then things would improve from there. It seems the reverse has happened. Just over a year ago I got the blessing from the chair the rigger's committee to go and jump the grey thing. Oh how things have changed.

The good news is that we now have a more solid definition of 'recognised manufacturer' from the BPA. The bad news is that it doesn't include me. To cut a long story short it now looks as though I am expected to become a BPA rigger and go away and do a degree in engineering, for insurance purposes. So that if anything ever happened, the BPA could defend themselves in court. That's basically the gist of it. It will be years before I can become a BPA rigger, and I really dislike the prospect and cost of going back to university. This may well be the end of 'My Little Project' in this country.

I am disappointed but not exactly surprised.

Share this post


Link to post
Share on other sites
Quagmirian

Bad news from the BPA. I really was expecting that when I started I would be taken for an idiot, and then things would improve from there. It seems the reverse has happened. Just over a year ago I got the blessing from the chair the rigger's committee to go and jump the grey thing. Oh how things have changed.

The good news is that we now have a more solid definition of 'recognised manufacturer' from the BPA. The bad news is that it doesn't include me. To cut a long story short it now looks as though I am expected to become a BPA rigger and go away and do a degree in engineering, for insurance purposes. So that if anything ever happened, the BPA could defend themselves in court. That's basically the gist of it. It will be years before I can become a BPA rigger, and I really dislike the prospect and cost of going back to university. This may well be the end of 'My Little Project' in this country.

I am disappointed but not exactly surprised.



So, how did they actually define a "recognized manufacture" ?

Also, engineering degree for insurance purposes? Heck, closest I can imagine you could get is aerospace degree but even that hardly discusses anything related to parachutes (besides aerofoils and stuff)...

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

0