The part about shear webs that does not make sense is, if you take two pieces of balsa, one with vertical grain and one with horizontal grain, the one with horizontal grain is much harder to break. I built two test spars, one with vertical grain shear webs and one with horizontal grain shear webs. While supported on both ends, I added weight until they broke. The horizontal grain shear web took 5 times as much weight to break. Where am I going wrong?