Pure bending in flight only when under positive g, but you must allow for the negative g limit loads causing column buckling, which as pointed out is usually the critical factor for a wing strut.
Note that the buckling load is independent of the tube's tensile strength, it's a factor of geometry and the elastic modulus... i.e. a 4130 tube will be no stronger in buckling than a 1018 tube.
Last edited by Dana; 11-05-2012 at 06:10 PM.
Does that 1928 strut include a jury strut in the middle? I hope it does, it would be weak in buckling if no jury strut.
I have seen several Piper Cubs that had collapsed rear struts from wind coming from behind (while tied down outside).
Cub owners will duct tape 2x4's to the rear strut to prevent this collapse on high wind days.