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Re: Leading Edge materials 11 Dec 2013 00:52 #623

Hi Phil,


I did make my leading edges out of 2 layers of carbon, but I'm not sure how much it took. I'll have to go back through my receipts to see how much I bought and how much I have left to see if I can figure it out that way. I used the 284 twill fabric that is 5.7 oz. I didn't use anything between the layers, but I did add an extra foam rib between the plywood ribs in the first 5 bays for extra support. I'm mostly just duplicating what Steve Arndt did on his Magic Dragon, as his has been flying problem free for many years now. I added the extra ribs because his sagged a little between the ribs, but he had done a static load test, to 5Gs I believe it was, without them and had no problems.


I had a long discussion with a friend that builds his own design rigid hang glider, and he uses Kevlar on the leading edges because of the better impact resistance. That might be prudent on a hang glider that occasionally hits the leading edge on a hard landing, but with a sailplane, do you really think it would be necessary? What would would be the situation where you be striking the leading edge that hard? On a hang glider you could drop the glider when landing, but on this glider you would be rolling in on the wheel. The carbon could handle any kind of normal banging that would happen transporting and assembling it. Kevlar doesn't have very good compression qualities and and can be a pain to work with because it is so hard to cut and drill. Carbon is stronger, stiffer, and not that much more expensive it think.


Cheers


Rick



From: Phil <This email address is being protected from spambots. You need JavaScript enabled to view it.>
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Sent: Monday, November 7, 2011 6:59 AM
Subject: Leading Edge materials

Hi Rick,

Just a quick question - I believe you fabricated your leading edges out of composites rather than use the original 0.8mm plywood in the plans. I'm trying to calculate the quantities of material that will go into my carbon dragon and was wondering how many layers of carbon cloth (and what weight cloth) you used.

Are your leading edges made just out of CF or did you use any foam or other materials between the laminates to add dhickness/stiffness?

I am considering using Kevlar cloth over carbon for my leading edges to improve its impact resistance but don't know if this will be stiff enough on its own.

Thanks,

Phil Lardner

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