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Aviation History
1937
1937 - 0881.PDF
APRIL I, 1937- FLIGHT. 335 MODELS A Promising Wake field Cup Design : Club News : A Useful Handbook By M. R- KNIGHT The "Du.racru.iser" CONSIDERABLE activity is centred on the production of models to the 1937 Wake field Cup formula, and several have now made their first flights. Among them is Mr. C. A. Rippon's Duracruiser, a cabin high-wing monoplane with divided, strut-braced ™ " —-• : "•*" wings, tapered and swept-back, and an unusually low thrust- line. With a wing area of 210 sq. in., a span of 43 in., and an overall length of 34, the total weight is 8£ oz. A vast amount of thought has been expended on the detail design, with the result that potential causes of trouble have been anticipated and guarded against. Aerodynamically and structurally, therefore, the machine is of exceptional interest. The fuselage consists of six longerons of | in.x| in. hard balsa, cross-pieces and the diagonal bracing in the top and bottom of the same material, and bulkheads formed from pieces of -pV in- balsa sheet, their mitred corners reinforced. Two pieces of thick celluloid form the cabin, and are stress-bear ing. Front and rear bays are reinforced with balsa sheet. The maximum width is 3 in., and the depth 5 in., of which the cabin accounts for 2 in. The thrust-line is 2 in. from the bottom of the fuselage. Each wing is 20 in. in span, tapers in chord from 6 J in. to 3J in. and has an aileron 6| in. x if in. set at a nega tive angle. The trailing edge is backswept 17 degrees, and there are 8 degrees of dihedral. The wing-section is RAF 28. Though not the most efficient aerodynamically, this form of wing has proved highly effective, particularly in securing a clean take-off. A single length of ^32 in.xj in. bamboo is used for the wing and aileron outline, and this is reinforced with shaped balsa to form the tapered leading edge. There are two spars of -^ in. balsa, tapering in depth from § in. to I in., and the ribs of -^ in. balsa are spaced 1 in. apart. The ailerons, which are hinged with aluminium, are built and covered integral with the wing, .and then separated. Each wing is braced with a vee strut consisting of three spars of A in. in. soruce, covered on each side with 35 in. balsa. Rubber bands pass through the strut from hooks on the fuselage to swivelling hooks mounted on a bamboo peg in the wing, thus securing the necessary "anti-crash" flexibility without any tendency to fracture. Two prongs of 20 s.w.g. wire on each wing plug into holes in a rW in. birch plywood strip cemented to the top longerons, and rubber bands pas sing over the fuselage are anchored to hooks on each wing. The struts are similarly secured to the bottom of the fuselage. Additional holes permit a variation in longitudinal trim. The detachable undercarriage comprises two struts and an axle of bamboo, sprung by means of rubber bands passing from hooks on the struts through streamlined tubes of rolled and gummed parcel tape, to hooks on the fuselage. The i\ in. wheels are of balsa. The tail-plane is 18 in. in span, the backswept leading edge tapering the chord from 5 in. to 2J in. The fairly thick sec tion has a flat under side. Bamboo is used for the edging, and T'g- in. balsa for ribs and main spar. The fin is 7 in. high and G in. wide, and consisti of -rs in. balsa ribs threaded on a spar of the same material and bamboo edging. Prongs of 20 s.w .g. on the tail-plane trailing edge push through holes in a plywood panel on the fin, and into the sternpost. A wire saddle on the front of the fin slips over bamboo prongs on the tail-pltme leading edge, and is secured by a rubber band around the fuselage. "Mikasa" tissue is used for all covering. The workman ship, as one would expect, is perfect. At present the motor is a single skein (14 strands) of \ in. x 1/30 in. rubber, an chored to a bone peg in the rear of the fuselage, but provision Mr. C. A. Rippon's Wakefield Cup model. It is of 43 in. span, and the workmanship is of an extremely high order. is made for the installation of gearing and for the use of a twin winder at the sternpost. The symmetrical airscrew is 16 in. in diameter, 20 in. in pitch, and 2 in. in blade width, with a free-wheel device in front. There is no rubber-tensioner. With the wings at 4 degrees positive incidence, the tail neutral, and the thrust-line parallel with the tail, stability and per formance have proved highly satisfactory. S.M.A.E. Contests in April DURING April two open contests will be held on the grounds of clubs affiliated to the S.M.A.E. Next Sunday, April 4, the Gamage Cup will be competed for on the basis of the best average of three K.O.G. flights by any type of rubber-driven model. On April 18, the Pilcher Cup will be awarded for the best average of three R.O.G. flights by models conforming to the 1937 Wakefield formula. Belfast on the Air LITTLE has hitherto been heard of model aviation in Ire land, but an interesting letter from Mr. H. R. Johnson gives news of what is believed to be the only club of its kind in Northern Ireland, the Belfast M.F.C., of which he is hon. secretary. An interview with the Founder-President, Mr. J. Black, was recently broadcast from Northern Ireland. Rallies THE 1937 "Northern Heights" Gala Day has already been announced to take place at Fairev's Great West Aero drome on June 20. On May 17 a Rally open to all clubs will be held by the Romford M.A.C., at Maylands Aerodrome. Details from Mr. J. S. Wreford, "Middlecot," Redden Court Road, Harold Wood, Essex. The progressive Lancashire Model Aircraft Society will hold their "Northern Rally " on June 6. The M.A.C. Grand Rally will take place at Wimbledon during September. A Valuable Handbook FRANK ZAIC'S Model Aeronautics Year Book has won a high reputation and, apparently, a circulation large enough to justify increasing the size of the 1937 Edition from 74 to 160 pages. It is a mine of information on theory and practice, the subjects dealt with including various aspects of stability, low-speed aerodynamics, choice of aerofoils, fixed and free wheeling airscrews, and the effect on design of the new weight rule. Capt. C. E. Bowden contributes a chapter on petrol model problems, and there is even an account of radio con trol experiments. Plans are given of seventeen outdoor rub ber-driven fuselage models, including A. Judge's Wakefield winner, and F. Rogerson's fascinating biplane, winner of the Canadian Wakefield Trophy. The eighteen petrol-plane de signs include a flying-boat. Gliders, outdoor "spars," and in door models bring the number to 81. Every serious modeller should possess a copy, which can be obtained from model stores, or 4s. 3d. post free from Mr. C. S. Rushbrooke, " Inns- brook," 14, Ennerdale Drive, Aston-on-Mersey, Sale, Cheshire.
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