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Aviation History
1955
1955 - 0930.PDF
40 FLIGHT, 8 July 1955 BOBOLINK TO DELTA . . . The P.10 as exhibited at the Paris Salon of 1919 was Boulton andPaul's first "all-metal" aeroplane—a description which must be qualified, however, with the remark that plastics were used fordie covering of the rear fuselage! In this design, also, was incorporated the first swinging engine-mounting, a feature whichwas to be reproduced in a number of B.P. designs thereafter. As the development of metal construction went ahead, theaerodynamic staff were concerned with the progressive improve- ment of twin-engined bomber design, the measure of which isapparent in the photographs on pages 45-47. In the wind tunnel they investigated the properties of various combinations of wing,body and engine-nacelle in order to minimize interference effects, and the fruit of their labours was the Sidestrand, of 1927, whichachieved a performance, in terms of speed, climb and ceiling, comparable with the best single-engined bombers of the day.Such were the circumstances of the times, however, that only a single R.A.F. squadron—No. 101—was ever equipped withthese fine machines. Historical notes for which we are indebted to Mr. W. J.Pickthorn, remark that a notable contribution to the success of Boulton and Paul metal construction, and one which was patentedby the company itself, was the continuous heat-treatment pro- cess, by which formed sections were drawn through electricfurnaces, mounted on drawbenches, at speeds slow enough to enable the strip to soak at the appropriate temperatures. Rapidquenching for hardening was achieved by the use of water-cooled dies at the furnace exit. Formerly steel strip had been deliveredfrom the makers hardened and tempered, and had been rolled or drawn in this state. This meant that, apart from the difficultyof forming, it was impossible to obtain uniformity of heat treat- ment throughout, and local variations in ductility caused distor-tion of sections in passing through the dies or rollers. The distortion had to be rectified by subsequent straightening opera-tions which were delicate and costly. All these difficulties were solved by the new process, for thestrip was formed in the soft state and was held straight through- out its heat treatment—itself controlled within very narrowlimits to ensure uniformity. Another of the company's inventions was the "locked-joint"tube, wherein strip was drawn to circular, or other tubular, sec- tions, a bead being formed along one edge of the strip, aroundwhich the other edge was wrapped inside the tube. By this means tubular members could be produced in stainless steelsand in other difficult materials which, at the time, could not be worked by the "solid-drawn" process. Moreover, some savingin weight resulted, since the limits of thickness in rolling strip were much finer than the limits of eccentricity specified forsolid-drawn tubes. Thus, it was frequently possible to use lockcd-joint tubing in a lighter-gauge material than for its solid-drawn equivalent. The same means was extended to the uniting of two strips by means of locked joints at both edges, to formspars of figure-eight section, streamline struts and other shapes. The company look back also with justifiable pride on the verylarge measure of standardization achieved with their metal sections. Box-type wing spars, for example, were made with arange of three standard web-section forms and six flange-section forms, providing eighteen basic spar shapes, each of which couldbe produced in strips of various thicknesses to cover a total range of some 2,000 spars, suitable for use in aircraft ranging in grossweight from 2,000 1b to 20,000 lb. Similarly standardized were struts, longerons and other members, and the system was appliedsuccessfully not only to the firm's own designs but also to such notable aircraft as the Blackburn Bluebird, B.2 Trainer, Riponand Shark, and to the Saunders-Roe London flying boat. The tendency in the later stages of development was to usehigh-tensile steels for the main structural members (wing spars, interplane struts, drag struts, longerons and the more heavilyloaded struts in the front fuselage) and light-alloy for the secondary components such as ribs, leading and trailing edges,lightly loaded struts and fairing members. An exception was the all-steel system of light-aircraft construction developed forthe Phoenix lightplane and widely used on the Blackburn B.2, wherein, instead of the normal riveting, spot-welding wasemployed, resulting in a very cheap and efficient method of manufacture. The company's experience in metal construction, and par-ticularly in the handling of stainless steels, was undoubtedly a deciding factor in its selection, in 1927, to collaborate with theRoyal Airship Works in the design and construction of H.M. Airship R.101. Of five million cubic feet capacity, the R.101was very much larger than any previous dirigible but departed The Atlantic under construction, with the Bourges la in the background. entirely from former practice in that steel was used for the mainstructural members of the frame instead of Duralumin. The detail design and manufacture of the entire main hull structurewas carried out by Boulton and Paul, and Mr. North (by that time a director of the company) acted during this period as con-sultant to the Director of Airship Development. The great size of the ship and the multiplicity of frame members obliged theBoulton and Paul engineers to go to extraordinary lengths in the calculation of sizes of individual members to avoid cumulativeerrors and in the accurate setting of assembly jigs to suit. So meticulously was this pursued that, when the frame was erectedat Cardington, every component went into place without the slightest hitch. The tragic loss of the great airship was in noway a reflection on its structural design or manufacture. In the late 1920s also, by agreement with Dr. H. C. H.Townend and the Department of Scientific and Industrial Research, the company undertook the administrative and com-mercial exploitation of the Townend ring patents. Numerous forms of the ring—many of them combined with exhaustcollector—were evolved and were widely employed, and patents were obtained and exploited in many countries. Experiments withthe ring were made in numerous aircraft, including the company's Sidestrand bomber, a machine of notable efficiency in respect ofdesign, construction and military effectiveness. As performance of the Sidestrand was progressively improved, so the difficultyof manning its guns became more pronounced. The company's answer to this problem, in respect of the front gunner, at least,was a power-driven turret, as applied to the Overstrand and later described. The success of this turret (and, the makers remark,the publicity it received) led to the acquisition, early in 1935, of the British rights for the de Boysson turret from the Societed'Applications des Machines Motrices, and this design formed the basis of subsequent Boulton Paul turrets. In his book I HoldMy Aim, G/C. C. H. Keith remarks: "I think very great credit is due to North for his enterprise. In this and many other The dirigible R.101, the entire main hull structure of which was the work of Boulton and Paul. The airship is seen moored at Cardington. G
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