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Aviation History
1909
1909 - 0566.PDF
SEPTEMBER 18, 1909. tion in the first instance, but for our own part we favour the other aspect of the case for the two points which it has in its favour, the first being that the better a machine is made the less liable is it to give trouble any way, and the second being that when it does get smashed a well-made article is always more easily and satisfactorily repaired than one which is half a wreck to start with. Moreover, there is always the consideration that a " Flight " Copyright. Diagrammatic sketch of main planes, showing the arrangement of warping-wires (indotted line), and the manner in which the rear edges of the planes are flexed. It is important to note that the front or entering edges are unaffected by this movement,remaining always perfectly straight. certain amount of risk attaches to flight, which it is gratuitous to exaggerate by neglecting any reasonable proportions such as using a decently built machine to fly on, and although, of course, a well-made glider will probably cost more than one on which less care has been spent, there is no reason why the old adage should not apply, " the best is cheapest in the long run." supply ; it has a weight of 36 sq. ft. to the lb., and the waterproofing is done by a celluloid treatment. The seams in the complete covering are diagonal, and each half of a deck, from an extremity to the centre, is practi- cally enclosed with a kind of fabric bag, the edges of adjacent bags are laced together in the centre, while at intervals the fabric is tacked down to the supporting ribs. In order to prevent the fabric being torn, a thin strip of wood is placed between the fabric and the heads of the nails. Main Decks. The skeleton framework on which the surfaces are stretched consists, for each deck, of a pair of transverse spars having a section 1 in. deep by 11 ins. At the ex- tremities these spruce spars are joined together by a piece of bent elm, a scafe joint being made between the two timbers, light ribs pass fore and aftAt intervals of 1 ft., DECK R.I&S , g p between the spars and overlap the rear spar to give a flexible trailing edge extending rearwards about 15 ins. The ribs consist of two small strips of rectangular section wood separated by distance pieces at intervals. Each rib as it is built up is curved to a template so as to give a camber to the decks of 3 ins. at the maximum versine. The method of fastening the ribs to the front spar, which by the way is rounded off to form a blunt cutting edge, is to secure the last distance piece to the spar by screws so that it virtually belongs to that member and, as it "Flight" Copyright. Sketch of the flexiWe-joint connecting the vertical struts tothe main decks. A slight notch is made at the lower end of the U bolt to keep the eye of the strut central. Timber and Fabric. The material from which Messrs. Clarke have con- structed the glider is for the most part silver spruce, a timber which, we understand, they are able to procure in 20 ft. lengths without a flaw. In one or two places where bent woodwork is required—as, for instance, the extension of the runners which carry the elevator, and the extremities of the main decks—American elm is used. The decks are double-surfaced with a special fabric of British make, which Messrs. T. W. K. Clarl.e " Flight" Copyright. Instead of pulleys where the warping-wires leave the decks,short lengths of Bowden wire sheath are used clamped to the rear spars, as shown above. were, forms a supporting tongue for the top and bottom members of the rib proper. The connection is then further strengthened by putting a light strap of metal round the spar and tacking the ends to the rib. Considered as a unit, the framework of the two decks, taken together, forms an example of the usual lattice girder work which has been commonly adopted on biplanes. In accordance with the Wright system, the machine built by Messrs. Clarke further belongs to the flexible type, that is to say, non-rigid joints are employed 570
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