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Aviation History
1926
1926 - 0159.PDF
MARCH 11, 1925 DURALUMIN CONSTRUCTION ON ORIGINAL LINES Some Impressions of a Visit to the Works of Short Brothers FOR very many years the development of aircraft construction in Duralumin was retarded, as far as Great Britain is con- cerned, by the official view that this material was not suffi- ciently reliable and consistent to make it advisable to employ it for parts that had to resist heavy stresses, in other words, for main-structure parts. Other nations, however, did not share that view, and in Germany several designers have employed the metal successfully for a number of years. Rather more recently, French designers have turned their attention to the use of Duralumin, and by now there are in France very many aircraft firms who use this metal exten- sively, and as far as can be gathered, the " snags " which were expected by people in this country have not materialised. It is true, that France has had a very real incentive to making an effort to develop Duralumin construction in the fact that aluminium is a plentiful home product in P'rance, whereas steel of the qualities suitable for aircraft construction has to be imported. Apart from this fact, however, several French through. The fundamental principle consisted in the use of a series of hoops or formers of L and channel sections, to the flanges of which the Duralumin sheet covering was riveted. The covering was stiffened against compression loads by longitudinal V-section strips, interrupted at the formers. This machine was flown a great deal after the Olympia show, and its clean lines resulted in a very good performance for the power of the engine fitted. After various delays, orders were placed for a few machines cf this type, and one was, we believe, tested to destruction at Farnborough. The " Silver Streak " may be said to have marked the beginning of Duralumin construction at the Rochester works of Short Brothers, and although orders have been none too plentiful, the firm has managed to forge ahead and to develop the special form of construction of which the " Silver Streak " was the first example, Changes have been made since, notably in wing construction, the spars of which are no longer circular section steel tubes, but built-up Duralumin box spars, AT THE ROCHESTER WORKS OF SHORT BROTHERS : A general view in the shop in which metal spars are made. Although capable of producing spars for very large machines, the equipment is by no means elaborate. aircraft designers hold the view that judged on its qualities •only, Duralumin offers advantages. In Great Britain, as we have said, development was re- tarded because of a certain official distrust of the material, and it is not until comparatively recently that a start has been made with all-Duralumin aircraft construction. For the change in the official attitude towards Duralumin as an air- craft material, Short Brothers, of Rochester, one of the pioneer aircraft firms of Great Britain, can claim a gocd deal of credit. Immediately after the war, Mr. Oswald Short, favourably impressed by the possibilities of using Duralumin, and with very considerable experience in rigid airship construc- tion to draw upon, decided to construct an aeroplane in which Duralumin was used extensively. This machine, the " Silver Streak," had an all-Duralumin fuselage, and wings having Duralumin ribs, while the covering was in the form of very thin Duralumin sheets. The wing spars, however, were in the form of steel tubes of circular section. The fuselage was remarkable on account of the form of construction, in which there were no longitudinals, or longerons, running right but as regards the fuselage construction, the original type has been essentially maintained. Comparatively recently the same principle, with miner modifications, dictated by local requirements, has been applied to the construction of flying-boat hulls, and one of these, built to take the standard superstructure of the F.5 flying boat, has now been in service for a considerable period, and has, we believe, given excellent results as regards durability and seaworthiness. A very great point in favour of metal hulls is, of course, the absence of water soakage which in large boats may amount to several hundred pounds. If a Dura- lumin hull is watertight, and so far the experience of Short Brothers has been that there is no difficulty in making such a hull watertight, the absence of soakage alone would appear to justify the use of such hulls. It seems, however, that with the forms of construction originated and developed by Short Brothers there is the further advantage that the Duralumin hull can be built with a very considerable gain in structure weight. If, as appears likely, protective coatings can be discovered which will prevent altogether the corrosion 139
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