Originally Posted by
speedracerntrixie
I think your calculations may be a bit high. For reference the last two giant scale airplanes that I owned with built up wings a Cap 232 97" had spruce spars of 3/8" square and a Reed Falcon ( Pitts Special type ) 72" has spruce 3/8"X1/4". Both used 3/32 vertical grain balsa for shear webbing. For some added strength you could also add trailing edge spars with shear webbing.
My calculations may very well be a bit high. However my plane will weigh 33 lbs with cargo and has a wing area of roughly 980 in^2. Its an unusual plane being designed for a competition. How do you justify the choice of spar size mathematically?