Welcome, Guest
Username: Password: Remember me
  • Page:
  • 1

TOPIC:

Re: Saving weight 13 Dec 2013 00:50 #796

Thanks Rick - those are useful insights and tips. It's always nice to learn what others would do differently the second time around ;)

I plan to make a number of comparison test pieces (ply/spruce, carbon & carbon/foam) and test them to destruction to see how they stack up against each other weight and strength-wise, and also to test my own ability to fabricate reliable carbon pieces. I'll check out the files in the files section.

I would like to eliminate as much of the wood as possible to avoid the humidity / deformation problems that I'm pretty sure our soggy Irish weather will create over time! I'll certainly be replacing the carbon tows with rods following from what I have read so ar.

I'm very much looking forward to seeing the second part of Steve Arndt's Magic Dragon video - the first clip was very useful to see and I have watched it several times to study it. Many thanks for posting it up.

All the best,

Phil.

--- In This email address is being protected from spambots. You need JavaScript enabled to view it., Rick Mullins wrote:
>
> 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 <philiplardner@...>
> 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.

Please Log in to join the conversation.

  • Page:
  • 1