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TLDR: how would you trace the outermost rib of a canopy?

I laid the canopy out on the floor and got a crude tracing of a Flik, Mojo, and OSP. There were very noticeable differences in the airfoil (comparing the Flik and OSP was very interesting) and so, now, I'm looking for a way to more accurately trace them out. On saturday I'm doing this for a Flik, Fox, Mojo, Troll, OSP, Outlaw, Blackjack, and Dagger (and any other canopies I might have access to).

In a perfect world I'd have 2 11'x3' sheets of plexiglass to sandwich it between and a light underneath. My current plan is to stretch out some sheets/fabric and pin the top of the outermost rib to the tensioned fabric, then lightly tension the rib and pin the bottom of it. My backup plan is to just do it the way I did my first tracings...but more carefully I guess lol.

I thought about getting the rib perfectly laid out and then taking a picture of them from above and using that picture and photoshop/autocad to trace the outline...however I'm worried about possible distortion / inaccurate representation of the airfoil that way (using a camera).

After tracing them out, I am going to scan them into my computer (and probably autocad) and make a table of the airfoil shape, canopy trim, and community consensus regarding opening / flight characteristics. I also want to use the results to decide on a rib shape so I can make a canopy.

Has anyone done such a survey before?

Thoughts? Suggestions?

P.S. Already contacted manufacturers; however, none would send any rib shape (which I understand I guess but not really??)

You're right. All manufactures should turn over their patterns so you can more easily reverse engineer their canopies. Please ignore the years of testing, sweat, and money that they put into the products we all use.

Get Dan Poynter´s vol 2.
http://www.parapublishing.com/sites/parachute/information/parachutes.cfm learn what makes an airfoil then one will understand how to measure it.
To what the the other poster said. I agree, There is not much difference between a survey of profiles and giving away industry secrets.
Take care,
space

I totally understand that argument. I wouldn't expect them to turn over their patterns and don't mind at all...it's business... however, the years of testing, sweat, and money provide them with reasons and motivations to make the airfoil a certain shape. Just by having the rib shape, I don't have access to the "why", which is pretty damn important. And the rib shape is easy enough to get with the canopy in hand.

I have that book and have read it more than once. It's an amazing book.

Another fantastically informative post by space.

Agree with both you guys. Dan Poynter just actually passed away recently. I reference this manual often.

having the airfoil section and the trim, youre still missing out on about 70% of what makes that canopy fly as it does.
the more extreme the aspect ratio of a wing is towards the low end, the less it is represented by the airfoil section alone (which works fine if you have an infinite span). so on low end of aspect ratios the 3d effects (like air beeing distorted by tip vortices, air not moving nicely along the cord, etc) become dominant.

the tricky thing with the base canopies that i found is, that without maybe some ueber duper software you practically cannot model them nicely on a computer. especially if you want to design something that behaves well in deep brakes / close to stall / stall, its going to be so messy, its not gonna work.
there are some really interesting things going on with you canopy if you fly it in different brake settings or flare it, be it that the planform changes, that due to ballooning , also the airfoil section changes where its not fixed by a rib, etc...

if you want to reproduce what manufacturers do, youll also need the top and bottom skin. especially the top skin, since a LOT of thought and experiment goes into that one to get it behave just as it does...

anyways, for tracing a rib... i did this once with a parafoil. so i suppose the most accurate way is to remove the seams all the way, get the rib out of the canopy, pin or tape it down on the floor, then trace it...

It surprises me the manufacturers won't work with you to get you what you need. At a minimum you should be able to purchase the part like a part for your car.
I understand the reverse engineering, blood sweat and tears element but it takes way more than a few measurements to reproduce a complex structure like a parachute or a water pump.
I could see the manufacturer verifying your qualifications to properly perform a repair but to say you HAVE to use THEM for a repair facility for their product seems excessive.
As for tracing out from a used part off the canopy I wouldn't expect the level of accuracy you would require to replace a part after distortion from stitching, repeated loading from openings and flight etc..
I was going to try this on a stabilizer replacement I did to a BASE canopy and man that thing was ugly once I got it off the canopy. I was able to get my hands on the measurements (CAD drawings) from the manufacturer and went to Apex with those measurements and they cut the part for me.

i suppose if the manufacturer knows you well enough and knows that your qualified, and really only want to do a repair and not a copy, youve got a chance to get parts or patterns of what you need.

besides that, theres more than just proper qualification and the right mearsurements that go into some major repair.

at atair i was told that every canopy is made on a single sewing machine, to prevent any deviations in shrinkage in the seams that could arise from using different machines. if a canopy comes in for repair, they dig up the documentation to see on which sewing machine it was done, and the canopy will be repaired on this very machine.

also they charge surprisingly little for repairs, even big repairs or alterations (like adding zp noze and vents), and are really fast with it, i really dont see any reason to complain, and for anything bigger than a patch i send my canopies to the factory...

There are independent repair facilities all over the place that don't use the same equipment used for production that are used on the repairs. It takes some know how but it is done all the time with very acceptable results.
For me it can be the challenge of doing the work and the journey more than the time or money savings. It is good experience. I have done major repairs and built complete line sets for my BASE canopies where I could have saved a lot of time and money by sending it out and having someone else do it.
The challenge is recognizing when it SHOULD be sent out for repair and knowing your limitations and the limitations of the equipment you have to perform the repairs with.

There's a liability for them there. They approve someone to do a repair, the canopy later fails (related or not), and now there's a rubber stamp from the manufacturer approving the now failed repair work. America.

i know, been there, done that.

i was just trying to point out that manufacturers are not only doing this to keep their patterns secret, but also because they can do some repairs the most accurate way.

but you seem to try to build a library of patterns of different canopies, which is something different...

anyways, as i already stated:


so im sure that theres quite a lot of independent repair facilities as you call them that have very good connections to one or the other manufacturer for which they do also major repairs.

To all on this thread.
I can unstitch a damaged rib/ nose/ stabi tape it back together and use a glue board and mark on the edges But it doesnt work on the darker colors so I must go to plan b which is a transparent usage. I have a lot of experience repairing paragliders.
Take care,
space

i just want to link this here:

http://www.dropzone.com/...h=25;guest=201219961

one of the greatest threads over there, a LOT of information about building canopies.

Wow!!!! Best thread ever. Thanks so much ☺️! I got nothing done at work today since I couldn't stop reading that thread.

Heh heh. Feel free to message me if you have any specific questions, I know a few people who may be able to help.