A structural element of an aeroplane comprises a sheath of thin sheet metal and a wooden core fitting closely within and completely filling the sheath, the core being held under endwise compression by means of metal discs or plugs forced into the ends of the sheath. In one form, Figs. 14 and 18, a sheath 4 is formed by bending a metal strip into tubular form and welding along overlapping edges, a core 5 being then inserted. Alternatively the metal strip may be wrapped round a core by rolling or drawing, or the sheath may be a plain or butt welded lube. Discs or plugs 7, Fig. 18, are welded to the sheath. An aeroplane incorporating elements formed as above described comprises stub wings 2 formed integrally with the structure of fuselage 1, Fig. 2, and main wing portions 3. Each wing includes three spars a, b, c, Fig. 3, each constituted by booms 8, 9, Fig. 12, connected by vertical struts 13 and diagonal braces 14 secured to the booms and to each other by gussets. The spars are interconnected by upper rib elements 10 and lower rib elements 11 having outwardly turned flanges 18, for attachment of the skin 12 and notched as shown to clear the booms to which they are secured by welded angle gussets. Supplementary booms 19 extend the full length of the wings, Figs. 3 and 4, and are disposed one at each side of spar b and supplementary booms 20 are arranged between booms 19 and spars a and c, these booms extending only part of the span, Fig. 3. Midway between booms 9 of spars a and b and of spars b and c, respectively, are disposed supplementary booms 21 extending outwardly beyond booms 20 but terminating short of the full span. Booms 9, 19, 20, 21 and upper and lower rib elements are interconnected by diagonal braces 22, Fig. 4, in the planes of the ribs. In addition, pairs of diagonal braces 23 are arranged as shown in Fig. 3 between booms 19 and 21 at the mid‐section of the wing. In the root bay of the wing, Fig. 3, booms 20, 21 are connected by pairs of braces 24 and booms 19, 21 by pairs of braces 25, Figs. 3 and 6, the latter being stabilized by struts 26. All connexions are effected by welded gusset plates. The internal structureof thestubwings 2 which is continuous through the fuselage, Fig. 2, is of the same construction as that of the root bays of the main wings and the connexion between the stub and main wings is by angle strips 30, Fig. 7, bent to the wing contour and secured one to the stub and one to the outer wing by welding the inner flange between the wing skin 12 and internal structure, the strips being secured to one another by bolts 32 passing through out‐turned flanges 31 of the strips and the margin of a bulkhead 29. Upper and lower spar booms, longerons, and gussets of each wing part merely abut on the bulkhead 29. The nose and tail portions of the wing comprise rib parts 33, 36, respectively, Fig. 4, secured to front and rear spars at rib attachment points and channel stringers 35, 37, respectively, Fig. 3, to which and to the rib parts skin 12 is spot welded. Wing tip 38 is formed by welding the overlapped edges of a shaped sheet metal shell to the main wing body. The fuselage frame, Fig. 16, 17, incorporates composite wood‐metal members and comprises longerons 39, vertical and transverse struts 40, and diagonal struts 41, secured together by spot welded angle plates 42. The corner angles are reinforced by braces 43 attached to the struts by welded‐on plates 44.
MCB UP Ltd
Copyright © 1939, MCB UP Limited