I would like to use West system on a foam wing with out having balsa sheeting, Giant scale
war bird . 81" can I do this and if so what weigh cloth should I use? Jack

Why would you rather not use balsa sheeting?
You will need to put on several layers of glass (probably 2 or 3 layers of 4 ounce cloth) in order to make it durable enough to withstand any kind of hanger rash and strong enough to handle the flight loads. You will probably end up with a heavier wing if you use glass only sheeting.
IMHO balsa is still the best material for making strong lightweight wing sheeting, for example if you look closely at most of jet kits on the market with composite wings they are using a sandwich of glass/balsa/glass for most of the wing skins.

I glassed right over the foam on my Byron F-16.
I believe the foam used there was the injection foam, very tight with the surface sealed no pores I used 1 oz cloth with Z poxy finish resin, then vacuume bagged.
It worked very well only minor pin holes, only one application of epoxy.
The parts are very strong and withstand all kinds of hangar rash. They are also very light. The whole plane weighs in at 11 3/4 lbs.
I have tried it over other foam products aand not been very succesful it just soaks up lots of epoxy.

Hope this helps Don B

All my Isobars and DC-10s are 2 lb/ft^3 blue foam
with one layer of 2 oz glass. 2 layers of 2oz along
the trailing edge, but the key is 4-6 inch
wide of uni 6 oz carbon for a spar. Even in the
Isoburst years ago, the wing did not fail, it just
left the plane. All elevators are 1 layer of 6 oz.

But Kevin is correct, drop your keys on it and
it will crack.

My advice, if you want to make a stronger wing,
make it thicker. Every time you double the thickness
of a wing you increase the strength by ~8 times.

Hope this helps..

Eddie Weeks

Eddie,

Are you vacuum bagging the parts or just applying the cloth & resin by hand? I've played with bagging small parts directly over cut foam with great results, but never had the guts to do a big airplane like that.

Bob

Just about all parts are vacume bagged, some
of the larger DC-10 parts, like the center section
were not bagged and it worked fine.

Here is a center section of the a DC-10 what was
melted due to a hot start.

It is three inchs thick, has 1/4 plywood spar with 6 inch
uni carbon over and under the spar and 2 oz glass over the
whole thing.

Eddie,

Good picture!

Forgive me if I don't ask you to ground crew for me