Per gsoav8r:</p>

"(#2) also a wing in flight under dynamic loads arent really comparable to a static truss. The FBD's given dont consider the twist or torque imposed on a wing during flight (lift),nor the torque imposed on a wing due to flap and aileron operation, nor...the rotational force imposed on a wing just from ailerons and flaps would further the argument for a vertical web grain orientation".</p>

First off, I agree with you, for the purposes of most R/C aircraft, vertical grain balsa shear webs work well enough. However, I question if they workbetter for the dynamic loads imposed on a wing during flight. I see the job of the wing spar assembly as exactly the same as a truss.</p>