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Saving weight 13 Dec 2013 00:53 #797

If you want to keep it light, then build it by the plans. I really don't think you can make it any lighter and still have a safe glider. Where they start gaining weight is when people start making "improvements" I'm guilty of that myself. I've made a few minor changes to make it look nicer, but I'm trying to exercise some restraint. I've built a light sport plane and I know how easy it is to say this little piece doesn't weigh anything, and neither does this one, but by the time you're done somehow you picked up 10-20 pounds. I'm putting the finishing touches on my wings and I used carbon for the leading edges. Most likely I added some weight rather than save by switching from the plywood. But I have seen some CDs with wood leading edges and they buckle with humidity changes. At the low speeds this glider flies it probably would not make much difference but I like the appearance of the carbon, plus I'm sure it is a bit stronger. When I build my next one ;), I'll probably build my mid span ribs with foam and spruce cap strips. In the files section here you can find some test results comparing to all spruce. That would save a lot of time and be as strong (maybe a little stronger) for the same weight. Steve's Magic Dragon is a work of art, but it is significantly heavier than the prototype.

If you have done any research on this glider you will have found recommendations to replace the carbon tows in the spar with extruded carbon rods. The spars were designed with the assumption that the tows were good for about 90,000 psi but are actually in the 60-70k range. The rods are good for 350,000 psi. I built my spar with carbon rod caps and fiberglass web. I'll let you know how it works when I load test it :)

I have the video Steve Arndt made going over his completed Dragon ripped and have been trying to upload it. My DSL speeds aren't that great and the file is 1.7GB and has failed the first couple attempts. It's really worth seeing. and I'll post here when I'm finally successful.

I hope you build one. We need more of these in the air.

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: Wed, April 27, 2011 4:30:35 AM
Subject: [Carbondragonbuildersandpilots] Saving weight


Hi Folks,

I am studying the CD plans at the moment with a mind to start building later this year and am wondering if anyone can offer any words of wisdom for saving weight.

Is there any significant weight saving to be made by entirely replacing the wooden parts with carbon fibre or will the various structures loose too much dimensional stability and become too flexabe? Can the main wing spars and ribs for instance be fabricated out of carbon?

Also, can anyone point me towards details of any essential modifications or departures from the original plans that should be made to improve the strength and/or handling of the CD? I have come across various snippets of information and suggestions, but little detail. Any advice or experience would be appreciated.

Thanks,

Phil.

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