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Re: steve's dragon 12 Dec 2013 23:35 #751

The Millennium hang glider is built with a carbon/foam D-tube. The leading edge is composite layers consisting of; carbon/Kevlar/foam/carbon/Kevlar. When you make a sandwich with foam separating the layers you increase the stiffness tremendously. That is why plywood is such a great material; it has thickness that helps mitigate wavyness and increase stiffness.
The later production Mills would forgo the Kevlar and be built with a carbon/carbon/foam/carbon/carbon sandwich.

Billj3cub

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On 6/29/2011 6:08 PM, russell wilson wrote:


hi kenny

lets talk about the leading edge skins/part on the dragon and what you wanted to achive.

what you were talking about acheving in relation to using modern composites to replace wood was a weight reduction to offset a slightly larger glider/wing/wing area.

its been a while since i read a book that had this information,to save me putting the wrong numbers can you please correct the following statement.

when you dobble the thikness of a panell/beam/laminate/sheet....
.the strenth goes up by how many times?was it 4?
and the stiffnes goes up by how many times? was it 8?

the point i am trying to get across is if you half the thikness of your leading edge scin you are loosing much much moor than half your strenth and stifness.

for the benifit of other people reading this kenny can you please correct me directly under the statement please.

water has a density of 1 that is a block of water 1m by 1m by 1m weighs 1000 kg

wood varies and ply has glue....ply floats in water....so its lighter...do you have the density of ply?spruse/fenolic resin....for the exersize lets say .8

carbon is 1.8
epoxy is i think 1.1/1.2/1.3 depending on what you use

a laminate done by hand by us ametors ....carbon epoxy....will be close to 50% of each with an estimated density of ....1.5

if you were to build a carbon scin/panel/part that was the same weight as a wood scin/panel/part.

it would be half the woods thickness.and it will get thinner as you chase your original goal to be lighter using modern materials.

the carbon pannel we are talking about is very thin...althogh the material it self is superior in tension and compression to the ply... becaus we have reduced the parts thikness by half and moor in an atempt to be lighter.... the part itself may no longer do its job.due to the large loss in strenth and stifness.

also carbon this thin acts like a spring compared to the ply...i say this becaus iv had a small pice of each in my hands.
russ.

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