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Plywood vs. carbon 12 Dec 2013 01:03 #731

hi george

my dragon is ply,is covered...but is not painted on the out side or varnished on the inside.
i am not the builder of mine.
are you sure the carbon's plans call for varnish and paint?

in relation to your material comparison...something does not seem right.

bothe materials have two parts... resin/carbon and resin/wood

fenolic resin has a density of 1.1..this is in your ply?red?
are you using west system epoxy in your carbon sample?..density 1.3?

your two samples are the same thickness and size right?

carbon has a density of 1.8
wood varies from .14 to over 1.0

in each sample you can varie the persentage of the two parts that make each sample.
and this will vary the density of each sample.

if you have a carbon sample 0%carbon/100 %resin...this is as light as this combo can be(unless we foam it)

if you have a ply sample(aircraft ply) 0% wood/100% resin...this is the heaviest this combo can be.

hand lay up carbon/resin usally comes out at 50%/50%..dosent it?density 1.5?
aircfaft ply looks like moor wood than resin to me..my guess is 80% wood 20% resin.with the wood density say .4 .5 .6 .7?

if the wood laminate is 4 parts wood and one part resin it would have a density somewere between .5/.8

see why im scratching my head ....thinking the diferance in weight between the ply and carbon....that you have put up... at orond 20% to 25%weight differance does not seem right?
my thinking is it should be closer to a 50% weight diferance.
it also dose not corespond with my testing/samples.

kenny is also qoting that 0.4 mm thick carbon is slightly heavier than 0.8 mm thick ply...for the entire leading edge skin...that is also close to a 50% differance in weight.

is your carbon 6 oz cloth?and how many layers are you using?
what type of ply/wood type?
is there a chance the wood is wet?
did you accidentally type 0.8mm carbon when you ment 0.4mm?



russ.



On Sat, Jul 9, 2011 at 10:07 AM, george_rf <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:





I have all these materials.
Two ply 284 style carbon non vacuum bagged open lay up is 0.8 mm thick and weighs about 85 grams.
0.8 bare plywood is 60 grams sq foot. Bu the time the plywood is varnished on the inside and fabric covered and painted on the outside it will be about the same weight as the carbon just painted.
Grain vise the plywood has about the same stiffness as the carbon however it will break much sooner then the carbon will.
Across the grain the plywood is obviously much less stiff and far weaker then carbon.






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