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Re: steve's dragon 12 Dec 2013 23:43 #756

hi keeny
iv got some ply here that was suposedly left over from the wing skins/d tube...couldent find my vernias...mesured with a ruler it looks like 0.8mm

russ.


On Thu, Jun 30, 2011 at 11:52 AM, Kenny <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:


I can run the numbers, but I need to know the thinckness of the ply
wood and the stiffness if anybody has it. I have data for the composites

Generally, for the same material stiffness the buckling allowable goes up as a function squared, the in-plane shear stiffness is only linear -- I think you might be confusing area?

Keep in mind that the stiffness of the carbon is MUCH higher than the wood as well, so you really have to run the numbers. It might also be that in common thicknesses, plus the curved shape, the plywood may be thicker than required. In addition to that, with the graphite fabric, you can tailor the lay-up to get the stiffness in the direction you want (i.e. more plies in the +- 45 degree direction, which helps with the shear buckling (D tube should react the torsion).

The density is around .06 Lb/in cu vs .1 for aluminum



--- In This email address is being protected from spambots. You need JavaScript enabled to view it., 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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