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Aviation History
1928
1928 - 0231.PDF
MARCH 29, 1928 If the fuselage structure is unusually interesting, the wing structure is no less so, although showing, perhaps, a less noticeable departure from Boulton & Paul's previous forms of wing structure. We believe we are correct in stating that this firm was among the pioneers of rolled steel strip wing spar construction, at least in its efficient modern form using high-tensile steels. And it is certainly the first British firm to standardize a scheme of construction by which all conceivable manner and sizes of wings may be built from standardised parts. Of the Eoulton & Paul method of manufacturing steel spars, nothing need be said here. Suffice it to point out that manufacturing processes have been evolved which allow of both rapid and cheap production. What is of interest is the system of standardising certain spar flanges, webs and fittings in a manner which gives a sufficient number of com- binations to meet well-nigh every possible demand without having to go to the expense of making special rollers and dies. A few of the standardised combinations of webs and flanges are shown diagrammatically in one of our illustrations. It will be seen that, with three standard webs, and six standard flanges, 18 different spars are produced, giving quite a wide range. Add to this the fact that further variety may be added by a change of material, even to a change from steel to Duralumin, and it will be obvious that the range imme- diately available is very wide. Incidentally, the accuracy of production is within 0-01 in., thus ensuring complete interchangeability, which is even more important from the point of view of mass production than repairs. It might here be mentioned that all Boulton & Paul strip is formed in the soft state, and hardened and tempered after forming. The rib design is very simple, and consists of channel flanges and tubular distance pieces forming the girder webs. This applies to the normal rib. At points where heavier stresses have to be withstood, modified forms are used, alsoof channel section, but with larger channels, and with channel section distance pieces. Several types are shown by sketches. The attachment to the spars of internal drag struts andinter-plane struts is effected via bridge pieces in such a manner as to impose no crushing stresses on the thin-walledspars, the loads being taken either on the bridge pieces or on bolts passing through the distance-tubes in the spars. Without being a very detailed description of the construc-ton of the " Sidestrand," the above notes should give a general idea of the types of structure employed. In the absence ofan explanation of the internal arrangement of the fuselage, which would necessitate a reference to equipment of a militarynature, about which nothing may be said, we must confine ourselves to stating that the load of bombs forming theraison d'etre of the machine is carried inside the fuselage instead of outside. In this way a great deal of air resistancemust be saved, and doubtless this fact has contributed materially towards the good performance attained. The Bristol " Jupiter VI " engines are mounted on thelower wing, the supporting structure being rather neatly triangulated in a manner to avoid torque reaction stressesbeing transmitted to the wing spars in the form of bending moments. The engines are hung on swivelling mounts whichgreatly facilitate inspection. The petrol tanks are situated in the fuselage, and number three in all, a front main, a rearmain, and a service tank. The full tankage is 260 gallons, of which 35 gallons represent an overload to lie used for longflights or some such special occasion, the normal capacity being 225 gallons, of which 65 gallons in the service tank,90 gallons in the front main tank, and 70 gallons in the aft main tank. The undercarriage of the " Sidestrand " is of simple two-wheeled type, with oleo-pneumatic telescopic " legs " of somewhat unusul design. A long stroke is one of the features [" FLIGHT " Copyright Sketches TII tl CTDFSTRAND I " : Some constructional details of the wings. 1 is a spar section, 211
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