I am looking at designing a wing for a light airplane. I am planning on using +6/-4 G load factors. Initially I am assuming a box beam centered on the aerodynamic centre of the wing. Later. I may look at a front I beam spar with a D-cell leading edge and a front longeron for taking torsional and drag loads. In any case, I am assuming a single main spar that would take all loads and at most an aft, auxilliary spar to mount control surfaces and possible flaps to. I am considering a single spar wing in order to save weight. I am applying the above load factors to the wing lift loads and to the chordwise vectors of the lift loads in the PHAA, PLAA, NHAA ans NLAA conditions. Are there any maneuvering load factors that are normally applied to wing drag loads or to the wing pitching moment that is produced by the wings camber and lift production? Also, when combining bending, shear and torsional loads which occur simultaneously, is an interaction formula that divides actual bending, shear and torsional stresses by their corresponding allowable stresses normally used, the sum of these adding up to a value less than or equal to one? What is a good source of information on the design of "thin shell" torsion boxes (as used in a D-cell) built of wood? It should detail proper design practices, allowable shear loads, effective widths of skin between flanges, etc.