Measurements of the degree of smoothness attained in a laminar-flow wing speciment (Short Bros.)

Abstract

This report describes tests made to determine the degree of surface smoothness attained in a 6-ft. chord wing specimen having two spars and a thin skin stiffened between spars by ribs and channel section chordwise members. The specimen was designed and made by Short Bros. of Rochester. The tests included measurements of the initial surface smoothness, distortion under load, proof and ultimate tests and compression tests on two short lengths of the upper front spar flange. These tests show that in order to reduce the amplitude of the skin distortions to the required limits the rigidity of the channel section stiffeners should be increased and possibly additional local stiffening near the front spar added. No permanent distortions of the wing beyond the allowed limits are likely to occur under service conditions. The compressive stress in the spar flanges at failure was 37,500 lb./sq, inch. Strut tests on 6-in. and 12-in. lengths of the upper front spar flange gave failing stresses of 59,000 lb./sq, in. and 48,000 lb./sq, in respectively.