Lateral Failure of Spars

It was concluded that after the critical span or depth-breadth ratio has been reached, the modulus of rupture varies approximately inversely as the first power of the span and of the depth-breadth ratio. The direction of the lateral deflection is alternate between successive supports. For this reason, we believe that rib spacing along the spar is more important in reducing lateral deflection than the distance between supports at the strut points. Furthermore, we believe that, within the limits of modern design, any increase in distance between strut points can well be compensated for by spacing the ribs closer together, providing the ribs do furnish lateral support.