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Aviation History
1920
1920 - 0347.PDF
-MARCH 25, 1920 THE HILD-MARSHONET SPORTPLANE THE Hild-Marshonet sportplane, which hails from the UnitedStates of America, was designed to meet the demand for a moderate-price aeroplane, built of the best materials andworkmanship. This little machine, the outcome of 10 years' experience in aeroplane engineering, possesses several note-worthy features, especially in connection with machines of its class. The particular machine shown in the accompanyingphotographs and scale drawings is fitted with a 20 h.p. two- cylindered air-cooled engine, but a second model, similar inevery other detail, is being equipped with a four-cylindered water-cooled engine developing 40 h.p. at 1,100 r.p.m., and The main spars are of I-section spruce, laid out in " A "formation—converging at the outer extremities. The ribs are of boxwood with spruce cap strips, secured with brassscrews. The fabric covering is sewn on the wing framework, and treated with five coats of Dupont dope and a final coat ofvarnish. , A single interplane strut, more or less of streamlinesection, is fitted on each side of the body, and above the latter an inverted V pylon forward and apyramid of four struts aft, serve as attachments for the upper planes. The interplane struts are built up of two Three-quarter front view of the Hild-Marshonet sportplane weighing 135 lbs. This engine, which was used with successin 1914, was designed by Mr. James C. Spainhour, M.E., who is associated with the designers of the Hild-Marshonetaeroplanes, and will be put into production for use exclusively in both the single-and two-seater Hild-Marshonet machines.It will be seen that the upper main planes, which have no dihedral, have their leading edges swept back, whilst thelower planes are given a " sweep forward " and set at a dihedral angle of 6°. The top plane is staggered forward,the angle of stagger at the body being 400, and, by virtue of the " fore-sweep " of the lower plane, at the tips, 120.This unusual lay-out of the wings not only makes for stability layers of three-ply veneer, reinforced at the centre with abevelled spruce strip, and at the edges with aluminium, all securely riveted together. The steel strut attachments arealso riveted to the strut. There are two flying cables and one anti-lift cable each side, all of TV in. diameter, and no turn-buckles are used. On the rear pylon, within easy reach of the pilot, is a quick-release lever to which are secured theanti-lift cables, and by means of which the pilot may relieve the tension of the cables, thus enabling the main'planesto be removed single-handed, with the greatest possible ease. This, of course, is a great advantage in a machine.of this type, enabling it to be stored in a very small spac e Front view ol the Hild-Marshonet sportplane both lateral and longitudinal, but allows ai> excellent range of vision. The chord of the top plane tapers from 5 ft. at the root to 3 ft. at the tip, the curvature and depth of the ribs varying to suit the chord. The lower planes also taper in chord from 4 ft. 6 ins. to 3 ft. N.P.L. wing section No. 4 is employed, this section having a high lift and a good L/D for the 40 angle at which the planes are set. (not more than 9 ft. by 20 ft.), and necessitating the minimum of labour and attention in erecting and dismantling. The interplane struts, it should be mentioned, fold against the surface of the upper planes and are secured in place by a catch. The ailerons are hinged to the rear spars of the upper planes. The tail planes consist of a triangular horizontal stabilising surface, to the trailing edge of which are hinged two elevator 347
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