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(unknown) 12 Dec 2013 00:56 #726

Um... no!

Steve Arndt substituted moulded carbon for the original ply when making the D-skins for his Magic Dragon, which he covered with 1.8oz Dacron and Super Flight System 2-part paint. Watching Steve's videos, where he did use 1/32" ply D-skins, in the horizontal stabiliser, it has very clearly deformed due to moisture - something I really want to avoid. Though he doesn't specify exactly how many layers (or the weight or orientation) of carbon cloth he used, Steve does mention that his carbon leading edges "significantly enhance the strength of the glider."

D-skins aside... watching his 'Magic Dragon uncovered' video I don't understand his use of mixed materials in the main wing spar shear-web. Steve used 1.2oz Kevlar from the root to the centre, and then, outboard of that, 1.8oz Fiberglass for 2 sections, then 3/4oz fiberglass for 4 sections and finally 1/2oz fiberglass for the remaining sections. Why does he use this mixture of Kevlar and fiberglass, and why not simply use carbon to save weight, or a single material throughout?

The original Maupin design calls for the main spar shear web to be made from just a single 1/32" ply with the grain running 45deg to its length.

Ultimately there is only one way to discover the truth - and that is to build comparison pieces (ply, carbon, carbon-foam sandwich) and test them to destruction before incorporating the stronger elements into the final build... and then load test (not quite to destruction!)

Although only mentioned in passing while making his videos, Steve shows the mounting holes for his own-design winglets. Does anyone know is these proved to be effective or beneficial to the overall performance of his Magic Dargon, and are there any designs or plans for them floating around?

Phil.
(in soggy Ireland)




From: This email address is being protected from spambots. You need JavaScript enabled to view it. [This email address is being protected from spambots. You need JavaScript enabled to view it.] On Behalf Of russell wilson
Sent: 19 July 2011 03:20
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Subject: Re: [Carbondragonbuildersandpilots] (unknown)




im not offended or worried about a bit of passion.

do we all agree that it is a waste of a builders time and mony and moor importantly dangerous to sugest that...... the d scins can be made lighter and stronger using carbon in sheet form,to replace the ply?
in this particular aplication becaus of the very thin part we are dealing with..when we half the thikness(we need to go less than half to be lighter) of the part we lose much moor in terms of strenth/stiffness than the superior carbon can give back.
it is also worth noting that the unknowen spring qualities of the carbon part at this thinness
could caus a catastrofic resonance/flutter situation.
also worth noting is that the collor black in the sun can reach 90 degrees celcius,most resins reach a melting point/ temprature to gel..TG of 60 degrees celcius.if your part is black.you will need to find a higher TG resin or paint white and incure a further weight penalty.

i do hope this debate on this particular material/part is over and between us all,we have dispelled the myth that thinner sheet carbon is better than standard ply.

should we look at the tail boom?is it better perhaps to scin it in ply?

russ...amator..ordinary person..not a profesional..can be wrong.

On Sun, Jul 17, 2011 at 11:06 AM, slrrls2000 <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:


Got awfully quite after that snyde remark the one group member made to the other.
Let's try to keep it cival and on the up and up. We have the best chance of fresh ideas and motivated builders. That is what Jim wantet...afterall.

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