My compliments on sharing your learning experiences. Sounds like your molds are in great shape, but you need some experience with layup techniques.

I suggest reading how the RC glider guys build composite planes. Particularly F3B models, which often see loads greater than 18g's over 3-meter wingspans!

Wing Weight
I suspect all of the weight of your wings is contained in unnecessary epoxy. I have vacuum bagged quite a few wings with either balsa, carbon, or fiberglass skins.

The main task is to:

1) completely wet out the cloth

2) Immediately get all the epoxy you can off of it. Use an old credit card, or squeegy. You have to work very gently with light weight cloth or you will stretch it. The strength of any epoxy (FG or carbon) matrix is in the combination of the two. Extra epoxy adds nothing to the strength, only weight. You should target a 50% epoxy by weight. So if you are laying down 3 oz / yd^2 and 2 yards of cloth (for 6 oz cloth weight), you should plan on using no more than 6 oz of epoxy.

Yes, balsa will soak up the epoxy. You can thicken it with cab-o-sil (or similar) a little to help the absorpsion.

You want to get all the epoxy you can out of the layup (after completely wetting out the cloth). The surface of the cloth should look almost dry after using the card to get as much epoxy out as you can. Certainly not shiny, just kind of damp.

I also suggest you stick with 1/16 balsa and not go with 1/32. You need some thickness in the skin to give it strength (resistance) to deformation.

I suggest a fairly light weight FG cloth for the surface layer only. This will give you a smooth finish for painting, etc. and many fewer pinholes.

Spar Comments
You mentioned using vertical grained balsa for the shear web. This is fine. What about spar caps? You need something to take the compression/tension loads. I suggest either pre-preg carbon from ACP or CST. For formulas to calculate the strength you might need, see the following link:

I'm not sure how your spar is built, but if the spar takes all the bending loads, then the skin only needs to be able to take up the torsional loads (twisting). This is best accomplished, as others have mentioned, by using all glass on a 45 degree bias to the spar. This 45 bias cloth layup will also help keep your ailerons from warping.

Trimming the edges
I suggest completely trimming the extra cloth. Before joining the wing halves, completely trim all surfaces so that they are perfectly flush with the surface of the flange of the mold. This is easiest done while the epoxy is partially cured. Easy to cut with a single edged razor blade, but stiff enough to hold it's shape. Then you require a relatively small amount of spooge (epoxy & cabosil) to join the wing halves.

My best wishes to you and your project. I am hoping we can all learn from each other.



Here's a few links

Glider Spar Design

Example of advanced molded F3B glider construction

ScrollSander page - molded fuses, seamless joining of fuse halves