MTK

Hi Scott,

The stab skins are 1/16", 5-6 lb balsa. The thickness from the factory is around .075" so I sand these down to around .062" at the root and around .050" at the tips. I've discussed taper sanding of skins before. Ribs for the stab are 1/16" balsa mostly (except the root, 3/32"), a mix of contest grade and 8-10 lb stock. Ribs for the wing are 3/32" thick and again a mix of contest grade and 8-10 lb density.

The wing skins will be slightly thicker, 0.070" at the root and 0.050 taper sanded at the tip. In foam wings I sanded the skins to thinner section but in this open bay structure, a bit thicker won't hurt anything. I haven't decided the rib spacing of the wing yet. Leaning towards 2" (19 ribs) but haven't ruled out 1.75" (22 ribs). The cut foam core stations make either approach simple.

It is fairly easy to control the thickness....I mark the surface with a magic marker and I know that it penetrates about 0.005". When the mark is sanded off, I stop and measure with a caliper.

The skins are stiffened and sealed with laminating (thin) epoxy on the inside. I rub off as much as I can with paper towels. Enough remains to stiffen and seal the inside surface. Each stab skin gains about 1 gram of epoxy from this treatment.

BTW, there are a few tools that are indespensible when building for lightness and precision: Various lengths straight edges in both inch and cm gradations; A good gram scale with precision to 0.1 gram; A simple height gauge with 0.001" precision (mine is not digital); a good caliper or micrometer with 0.001" precision (don't need to be digital but it helps).

EDIT- I forgot the spars. The stab uses 3/32" square spruce and the wing will use 3/16" thick basswood, tapered from 3/8" at the root to 3/16" at the tip. Firm balsa can also work fine but I have the basswood and spruce already so why not? Weight between firm balsa (about 16 lb density) and basswood or spruce is very near a wash.