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Aviation History
1920
1920 - 1201.PDF
NOVEMBER 18, 1920 j'liiiiiiiiiiiiiiiiniiiiinniiii titiiiiiiiimimiMiniiimiiimiimimiiiiiiiiiiiniiimiiiiini,.ii,i.,l,,,.........,,,M,,..,,,.1,,,,,.,,,,t,,,,,MW,, „„„„.....MODEL -All communications should be addressed to the Model Editor. A stamp should be enclosed for a postal reply A 600-yard Monoplane known in the model movement, it was unanimously decided IHE machine shown by the accompanying drawings, whilst to elect Mr. James McBirnie as Secretary, the present Secre- being specifically designed for distance has, nevertheless, tary, Mr. A. H. Akehurst, being unfortunately unable to created a duration of 73 sees. The requests from readers for continue in office for business reasons. Mr. McBirnie is one this type of model and matters relating to it tempt me to of the early aeromodellists, and will, one is certain, fill the deal with such a machine in the series of models I intend, as post quite satisfactorily. Messrs. A. E. Jones, also well known previously intimated, to describe. The frame members are as the first firm in the model aeroplane accessory business, made of spruce, channelled in cross section, to the dimen- were represented in the aforementioned meeting by Mr. Moss, sions specified on the drawings. The bamboo cross members This firm, it is well to set on record, have consistently sup- are let into the channels at the distances noted by means of the usual fishplates and binding ; their purpose is to give rigidity and the necessaVy propeller clearance. The rubber hooks are of the customary piano wire form. Bracing is passed from corner to corner of the bays formed by the • cross members, to resist the torsion of the rubber when the latter is in tension. The chassis is formed from piano wire of 18 S.W.G. braced in a fore and aft direction as shown in the side elevation. Sufficient propeller clearance should be given, and also a " starting angle " when on the ground. This can be adjusted by sliding the rear chassis in a fore and aft direction, as desired. The rear chassis consists of cone skids. Such an arrangement, where records are concerned, is quite sufficient to get the machine off the groundw and also to protect the screws. Use disc wheels (as obtained from our model adver- tisers) of 2-inch diameter. The main plane is cut from spruce, the ribs being of birch and cambered. The rear spar is bent to theswept-forward form given by the plan view. The warping threads impart the dihedral angle (see side elevation). The elevator is made from wire, with ribs bound and soldered into their correct position as given by the plan view. The downward-projecting central spoke adjusts the incidence by being a friction-tight fit within its seating. The screws should preferably be of bentwood for distance work, otherwise carved ones should be used. Arrange the screws to revolve outwardly when viewing the machine from the rear, as I have found this to give not only better directional stabilty, but greater thrust. The detail drawing given separately shows the correct method of forming the shafts. The band of tin is first pressed round and the joint soldered, and then finally squeezed into place as shown in the lower detail. I trust the drawing makes this matter clear, as many readers complain that they are unable to make a rigid job of this piece of construction. The K.M.A.A. AT a meeting held recently (when the writer owing to illness was unable to be present) of various persons well ported model aeroplaning from its inception as an organised hobby, and the number of prizes they have given (many of them anonymously) are tribute to the fact that their interest is not merely backed by business motives. Will all persons interested in the K.M.A. A. please communicate with Mr. W. H. Akehurst, 27, Victory Road, Wimbledon, without delay Care of Rubber THE most vulnerable part of the model aeroplane, the rubber motor, is often so carelessly looked after that the dealer supplying the rubber is blamed for selling inferior goods. The best quality, unless well lubricated with a pure lubricant, will snap before worn out. Again, rubber of too great a cross section is often used. There is no need' to use J-in. strip rubber on models of i\ oz. or less ; £-in. strip is quite good enough. Apart from exposing a greater area to the action of the lubricant, this enables the torque to be imparted at a more even rate, and also makes possible a longer length of flight by virtue of the greater number of turns available. General Proportions BRIEFLY, it can be stated that with single screw machines the propeller should not exceed £ of the span, the latter being about $ of the total length. The pitch of the propeller should be ih times the diameter and the blade width £ in. to TV of the diameter. The wheel base should equal thediameter of the propeller. With twin screw machines the length of the machine can be twice the span, and the screws may be T5j of the latter in diameter ; the pitch should never exceed 3| times the diameter, when the pitch angle is 450. Replies to Correspondents A.B. (Leicester)/—1 am replying direct to your letter as soon as I have looked into the matter. J. van M. (The Hague).—I will give the desired drawing of the screws shortly. H. B. (Leicester).—Many thanks for your interesting letter, which I hope to publish in the near future. A. H. A. (Wimbledon).—I am sorry that a recent illness prevented me from attending the meeting. J. A. C. (Blandford).—I replied direct. 1303
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