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Aviation History
1942
1942 - 0248.PDF
t>6 JANUARY 29TH, 1942 THE SHORT STIRLING Two more factors influenced the design: The wing span was limited by the Air Ministry to 100ft.—from considerations of hangar space, one presumes—and the fuselage dimen sions were largely determined by the size of packing case needed. Within those restrictions the Stirling took shape. There seems to be little doubt that if the designers had had a fret- hand they would have chosen a wing of greater span and higher aspect ratio for efficiency. On the other hand, it may well be that had such a wing been fitted the amazing manoeuvrability of the Stirling would not have been achieved. As it is, pilots say that the machine can be "thrown about" almost like a fighter, and in a scrap that is a feature well worth having, and has doubtless played its part in making the Stirling such a formidable antagonist. Well-tried Methods In the primary structure of the Stirling one fii|ds obvious evidence of its flying boat ancestry. The wings are almost identical, so far as the type of design is concerned, with those of the Empire and Sunderland boats. The fuselage, apart from the fact that it has, of course, no step, shows a form of construction very similar to that of the boat hulls. The outward shape of the fuselage is a very straight top, a flat bottom, and nearly flat sides. The corners at top and bottom longerons are, of course, rounded off. Frames are of Z-section, and the longitudinal stringers are a cross between V- and I' sections, that is to say, a U with corners instead of a smooth curve. For many years it, was the practice of Short Brothers, in their flying boat hulls, to cut the stringers at the points of intersection with the frames, and to attach them by gussets. In For a four-engined aircraft the instrument panel and controls of the Stirling are very simple. The reason is that a flight engineer is carried, who has his separate instruments elsewhere. the Stirling • iuselage, however, the stringers are continuous and the frames notched for them. From a strength point of view there is prob ably nothing to choose between the two methods, but it appears likely that in assembling, the type of construction chosen is slightly quicker. As high speed in addition to great load-carrying capacity was demanded, everything possible had to be done to obtain a smooth finish. This meant that all external rivet heads had to be flush with the surface ; it also meant that free edges of skin panels could not be tolerated, but had to be joggled at the joints. All of which added to manufacturing difficulties, but was,t presumably, deemed necessary. One does rather wonder whether the few miles per hour thus gained are worth the extra trouble. If the surface were left smooth the saving in drag might be considerable, but by the time it is camouflage painted there is probably • not much gained. Wing Structure The wing structure, as already men tioned, follows closely that of the Short flying boats. Basically it is a two-spar structure, with spar flanges of extruded T-section, and top and bottom flanges connected by a tubular N-girder arrangement. This form of construction has been found excellent in the boats, and there wasirthus no reason for changing it in the landplane bomber. One minor change is thafc^ the inter-spar bracing is now of the^K The motor cyclist in the foreground gives " scale " to this pict_ specimen shows it to be intended for daylight operations ^5§ the Stirling. The camouflage painting of this particular two side-by-side tail wheels may be noted. J7^
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