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howardyin

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I also do similar thing with cnc hot wire. And i do make a lot of tests on peeling fiber from foam. Only one resonable approach was to san foam with 60-80 grid, cris/cross pattern, not circles, put some thick epoxy, squeze it down, and then make layout. It was ok on quaility side, but not constant. I did got 40-60% foam on fiber after peeling.

But it was hard to replicate on bigger surfaces and it was to be on wet side + around 200-350 grams of extra epoxy per m2 just to cover scratches to avoid dry bond. and next layer have to be on wet side too.
for two layer CF (200g+200g), I got 900g to 1kg for one sq meter(I will check record tomorrow, to find if I am remenber wrong numbers, ), seems happen what you said . (did like Mike 's video with first put some micro on surface)
 

stanislavz

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for two layer CF (200g+200g), I got 900g to 1kg for one sq meter(I will check record tomorrow, to find if I am remenber wrong numbers, ), seems happen what you said . (did like Mike 's video with first put some micro on surface)
Yes, around 1kg of total weight for 400gsm of cf fiber. And plus 100-200 grams more on filler to make it perfect.

On the other hand - plain/thick epoxy or just lower temperature in workshop gives you 700 gsm per lamite with 450gsm of fiber if you laminate it between two foils and just roll extra epoxy out.. or it gives you 600-650gsm of fiber if you stick to 1000gsm of laminate. Put this laminate with foils into you left overs from foams - you have your skin done.

And that one is on pair with single skin solution with 75-100mm separation of stiffeners in ribs forms. And if done in simple negative mold - minimum or no filler..

Maybe not ok for 200mph airplane, but ok for 198.7 mph one.
 

wsimpso1

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That works out to a total of 21.5 oz/yard.

Most wet fiberglass laminate is about 50% by weight epoxy, vacuum bagged laminate about 40%, so this is covered with about 11-13 oz per yard. While that skin is probably plenty strong for flight loads, most fiberglass over styrene foam surfaces are more like 21 oz/yard just to be adequately impact resistant for handling, bird strikes, etc.

Sailplanes using carbon over PVC foams (much stiffer and stronger cloth and stiffer foam) use 6 oz cloth, 200 g/m^2, while the folks building fast airplanes out of carbon and PVC foam tend to build two plies of 200 g carbon on the outside.

This laminate may tend to be fragile, and may require very careful handing both in build and once flying.

Billski
 

stanislavz

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Most wet fiberglass laminate is about 50% by weight epoxy, vacuum bagged laminate about 40%, so this is covered with about 11-13 oz per yard.

Yes , but if your underside structure will allow to flex it a lot, it will de-laminate very very easily.. Sorry for being sarcastic. Thicker one will be more sturdy..
 
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wsimpso1

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I just did a quick calculation of a 18" square tube with quarter inch foam core, using graphite BID 6 oz cloth on the outside, glass BID 6 oz on the inside, even included the graphite UNI tapes top and bottom. The graphite skins provide about 88% of the fuselage bending stiffness.

The glass inside the fuselage is making the sandwich work so it is sturdy against skin crippling and give something to attach bulkheads and internal structures to. But it sure is not doing much for transmitting loads between wing root and tail planes... And that may be plenty.

Billski
 

sming

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Nice use of laser cutter for the jig!!
But now we want all the details on the engine and redrive!! Gaokin 1000cc? Price? Can you ship it to the world?? ;)
 

howardyin

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May 23, 2020
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Nice use of laser cutter for the jig!!
But now we want all the details on the engine and redrive!! Gaokin 1000cc? Price? Can you ship it to the world?? ;)
Gaokin 850cc, about 1300 usd. The saleman told me that if I want to buy more , they only sell 5 or ten units one order . :(
 
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