Strengthening Wings on Over-Powered Aircraft
There are several ways to strengthening wings on foam aircraft when using .25 or .26 engines. Please note that most foam aircraft are not designed to use these engines and the resulting speed they produce. So, some additions are necessary.
Add carbon fiber between the foam leading edge and the balsa leading edge cap strip using 15 minute or longer epoxy. Be sure to use plenty of epoxy wiping the excess off after assembly. Use masking tape to hold the assembly together during the cure. Using this method, I have seen aircraft with carbon fiber reinforced wings fly through other aircraft without sustaining any damage.
Next, using a pencil, make foam holes in the foam wing join to form "nail holes" for the epoxy to fill into and making the joint stronger. Do not skimp on 15 minute or longer epoxy wiping off the excess after assembly. Always use fiberglass tape over the joint as epoxy does not soak into foam but rather just sits on the surface. So, the joint is only as strong as the foam next to it. Taping is absolutely necessary.
The best way to strengthen a wing is to add a strip of 3 inch wide 3/4 ounce cloth to both the top and bottom of the wing along the thickest part of the wing and coating it with fiberglass finishing resin. Then apply the regular 3/4 ounce cloth over the top of the strip. The resulting wing will be very ridgid and will not flex. I have cartwheeled an aircraft down the runway destroying the fuse and the wing remained intact. Note that 1 inch wide 2 ounce cloth can be substituted for the 3 inch but I feel that the 3 inch works better.
Please note that, in any case, always wrap the 3/4 ounce, wingcovering, fiberglass cloth aroung the leading edge, both top and bottom, always covering the bottom wing first and then sand.
The only strenthening to the fuse that I recommend is to add 1 inch 2 ounce glass cloth to the tail secion under the horizontal stab about 8 inches long. Anything else just add weight and will not give you any benefit.