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Aviation History
1911
1911 - 0098.PDF
[fUCHf] FEBRUARY 4, 1911. A POWER-DRIVEN BLERIOT MODEL. By E. TEMPLE ROBINS. SOME few weeks ago, having several ideas I wished to try practically, but being without the means of trying them on a full-sized machine, I conceived the idea of building a model which should be large enough to give results that would com pare favourably with those of a full-sized aeroplane. Still a difficulty remained. The model incorporating these new ideas might possibly fly and yet be extremely inefficient compared with those already on the market. The machine I wanted was a monoplane, so I at last decided to build a model Bleriot. This done I had only to dismantle this machine, decide the ideas to be tested, and compare the two sets of results to decide which of the two was the better. ^The scale was fixed at 3 ins. to 1 ft., and the only difference between the model and the full-sized machine is that the wings taper off more at the ends, this being done to reduce the turning moment of side gusts of wind. The dihedral angle is perhaps also slightly more pronounced. The fuselage is composed entirely of ash, the wood being obtained already cut -| in. square. This was well planed down and the edges chamfered off. The nails (round and large-headed) served the double purpose of joining the wood work and providing a means of fixing the stay wires as shown in Fig. 1. The whole of the framework was first nailed, leaving the nails still projecting about J in. After the piano wire (26 s.w.g.) was fixed and well tightened the nails were driven home. The chassis caused me some thought until I discovered a rather novel material for use in models. This is what iron mongers term bird-cage wire. It is apparently a very mild steel tinned over, and I found that size 10 s.w.g. provided an ideal material for taldng an 1 in. Whitworth thread. The forks and axle for the two front wheels and the method of fixing same can best be understood from Fig. 2. This same wire threaded at the ends served admirably for the upper and lower pylones or cabanes. The wings are made in the following manner, which made an extremely strong and neat job of them and yet allowed suffi cient flexibility for warping. The ribs were cut out solid from &in, canary wood, this being best done with a fret-saw. After being smoothed up with sand-paper two holes, one \ in. square situated 3 ins. from the leading edge and the. other \ in. by i in. six inches from the rear edge, were cut out. The «dges were next slotted, as in Fig. 3, to receive the ^ in. square wood upon which the fabric rests. The ribs were now spaced out on the two spars and secured with small brass nails. The J in. square wood was secured in the slots with •& in. brass nails. For leading and trailing edges of the planes I used a continuous length of half-round cane, steam bent to the curve and secured to the ribs with small screws. The particular cane used was of an extremely fibrous nature, solid and without nodes. Small screw-eyes, fixed into the main spars, are used for holding the wing, and warping wires, the knots being soldered to make them secure. The method of securing the planes to fuselage is seen in section through A, A. The angle of dihedral is 50. The small bolts holding spars being made of bird-cage wire. The rear spars are merely slipped loosely into holes (C in drawing), thus allowing easy movement during warping. The wood in which holes, C. are cut has also screw-eyes fixed in it to which the control wires are taken, steering gear and cloche being discarded as too heavy a refinement ===jl for an experimental model. Tail and elevators are made similarly to the main planes with the exception that the front spar is replaced by an aluminium tube, into which a smaller tube, upon which are the elevators, is telescoped. The rear spar is also brought forward to the centre of the plane. The centre and side ribs, of the fixed portion of the tail, are fairly substantial, as through these are passed the bolts holding it to the fuselage. If these bolts are made with fairly long threads a fair adjustment in the lifting effect of the tail can be made irrespective of elevators. This will save considerable time should the engine be slightly out of its proper position. The fabric on wings and tail planes was first laid over the frames and then tightly sewn along the back and sides. The underside was afterwards tacked to the ribs with brass tacks, thus forming the under curve and also tightly stretching the fabric. The rudder plane was made with an edge of umbrella ribbing strengthened with 18 s.w.g. bird-cage wire. Two cross wires were passed through'the ribbing to fit, when bent, into tin- plate hinges on the fuselage. The accompanying photographs and sketches will no doubt serve to explain any parts I have failed to describe. In case the reader should imagine that this is an expensive machine to build I give below the cost of the various materials used in it. This is, of course, not taking into consideration the engine, which should be about i-h.p. My machine is at present fitted with a -J-h.p. model petrol engine weighing complete 8 lbs. and I have had several long hops with it although the engine is a " home-made " one. My intention is to fit a i-h.p. engine, of which several are sold weighing considerably less than my £-h.p. one does. By thus reducing the weight and also increasing the power, I feel sure it should fly successfully, as during the hops the balance and landing Views of the framework of the model. Views of the model complete. 100
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