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Aviation History
1953
1953 - 0624.PDF
618 FLIGHT, 15 May 1953 DURESTOS GLIDER WING Artist's impression of the M.76 design, which features the Durestos wing. The two-seat machine is developed from the aircraft which won the 1947 B.G.A. design contest. ONE of the most interesting projects undertaken by the plastics division of F. G. Miles, Ltd., during the last three years, has been the construction for the British Gliding Association of an experimental wing—moulded in phenolic-impregnated asbestos material—for a high-performance glider. The machine, known as the M.76, is a development of Hugh Kendall's Crabpot I, which gained first place in the 1947 B.G.A. 2-seat design contest. Financial backing for the project has come from the Miles company, the Kemsley Flying Trust (through the medium of the B.G.A.), and the Ministry of Supply.' The effect of the chordwise position of boundary laver transition on a sailplane's performance is great, for laminar flow over an increased fraction of the chord gives a much reduced minimum drag coefficient. The achievement of laminar flow over as much as possible of the wing has been hampered in wings of normal construction by surface waviness, and it was felt that one way of obtaining the required improved finish would be to use some form of stabilized plastics construction. It was decided to use a phenolic/asbestos fibre material stabilized with a paper honeycomb, the manufacturing technique being based on the vacuum moulding process pioneered by the R.A.E. at Farnborough. The 60-ft span wing was to be made in two semi-span sections each consisting of one 30-ft moulding— probably the largest one-piece moulded phenolic/asbestos struc tures yet manufactured. The method of construction is, briefly, as follows :— (1) A model of the wing, with exactly the same shape as the wing itself, is made from concrete, steel and a phenolic/asbestos material. (2) A layer of soft phenolic/asbestos material is placed upon this model and made rigid by heat cure. This is called the master finer. (3) A further layer of phenolic/asbestos material is then placed on this and heating mats and thermocouples are put in place and again heat cured. The shell produced is the heart of the main mould. (4) This mould is then supported in place and covered with concrete. (5) To make a wing, the soft Durestos felts are cut to shape and placed in position on the loading table, together with the paper honeycomb (Dufaylite) filling. The outer felts are then laid in place, and the table is lowered over a loading trolley. (6) The loading trolley and soft felts are then moved into the mould. A rubber bag is used to seal the felts and apply suction. (7) Electrical heaters driven by a 112 kVA generator are used to cure the product, and after about six hours the complete stabilized wing skin is cured. (8) The wing is then removed from the mould and after trim ming is ready for the fitting of ribs and trailing edge closing member. The steel root fittings are moulded into the wing in situ at the time of cure. In developing this method of construction, the company has had to face a number of original problems resulting from the use of the new materials. Mould cracking due to temperature vari ations in the concrete mass and to pinching action of the cured phenolic/asbestos mould surface, and the inconsistency in quality and effect of certain apparently identical mixes of resin, were among the setbacks experienced. A really close liaison between design staff and the operatives has proved invaluable for the successful introduction of the new techniques. The date when the M.76 will fly is still some time ahead for, up to the present, only starboard wings have been produced, and the glass fibre ribs and trailing edge member, and the ailerons, have not yet been fitted. R.A.E. tests are about to commence, and the first public view of one of the moulded wings will be at the British Plastics Exhibition. The main value of the Miles project is clearly wider than that of the particular wine; it lies in the "know-how" of the techniques of this method of moulding. For the future, further applications are inevitable—and a number are already being considered. The possession of a two-seat machine such as the M.76 would obviously be a good thing for Britain in the 1954 world champion ships. To guard against delays in the production of the plastic wing, a wooden wing to the same specification is being constructed by Elliotts of Newbury, and is to be fitted to the conventional wooden fuselage built by Miles. CLUB AND GLIDING NEWS THERE are 20 entries for the Wolverhampton Aero Club's Goodyear Trophy Race, to be held at the Municipal Airport, Wolverhampton, tomorrow (Saturday, May 16th). The pilots and their aircraft are as follows (the pilots are also the entrants, unless otherwise stated):— Miss L. E. Curtis (Wicko, Gipsy Major 1), R. R. Paine (Miles Hawk Speed Six, Gipsy Six IF), D. J. Bennett (Proctor 5, Gipsy Queen 3), H. J. G. Turner (Proctor 3, Gipsy Queen 2), F. Dunkerley (entrant, D. J. Adie, Miles M.28-6, Cirrus Major 3), G/C. C. M. M. Grece (Miles Nighthawk M.7, Gipsy Six 2), D. F. Ogilvy (Moth Minor, Gipsy Major 1), J. N. Somers (Mew Gull, Gipsy Six 2), D. J. Jemiuett (Miles Hawk Trainer 3, Gipsy Major iC), W. P. Bowles (Messenger 2A, Cirrus Major 3), G. G. Alington (Tipsy Junior J3, W. Mikron 2), J. P. Growther (Proctor 3, Gipsy Queen 2), P. Fillingham (Chip munk 2, Gipsy Major 4), G. R. I. Parker (entrant, R. Blackburn, Proctor 5, Gipsy Queen 2), H. C. Willson (Messenger 2A, Cirrus Major 3), P. Hillwood (Proctor I, Gipsy Queen 2), S/L. J. Rush (Falcon Six, Gipsy Six), A. J. Spiller (Leopard Moth, Gipsy Major 10), A. S. L. Paine (Proctor 1, Gipsy Queen), G. C. Marler (Falcon M.E.B., Gipsy Six. The race begins at 3 p.m., and will be preceded at 2 p.m. by a flying display, with Service support; the French Stampe squad ron will also take part. Visiting aircraft must arrive by 1.30 p.m., and a buffet lunch will be available for their crews. Admission for the public is at 2s 6d (children, is 6d). JUNE 20th is the date scheduled for the 1953 National Air Races, to be held at the Municipal Airport, Southend-on-Sea. The programme includes the Grosvenor Challenge Cup, the Norton- Griffiths Challenge Trophy, the Kemsley Challenge Trophy and the King's Cup races (see p. 597 for entries) and also a display. CLUBS' flying-time totals for April include Denham Flying Club, 153 hr; Elstree Flying Club, 200 hr; Fairoaks Aero Club, 241 hr; Strathtay Aero Club, 177 hr; and the Yorkshire Aeroplane Club, 181 hr. THE fifth International Air Rally of the Yorkshire Club will be held from June 5th-7th, and will be centred at Harrogate. Guests from nine countries have already accepted invitations, and a full programme has been arranged. THE opportunity to learn to fly at no personal expense is offered by the Elstree Club to the fortunate person who fills their present clerk/typist vacancy. C.F.I.-cum-manager David Ogilvy is looking for an aeroplane enthusiast who doesn't object to "the odd hours so essential with a flying club." A TECHNICAL description, performance data and three-view plans of the Dart Kitten are contained in the April issue of the Popular Flying Association Bulletin. Similar treatment of the J. A.P. J.99 engine (which powers the Kitten) this month is to be followed by a series describing other ultra-light aircraft and engines. P.F.A. announces tbat the Wycombe Flying Group are planning re organization, with the intention of purchasing their own aircraft. FROM Lasham comes news of an 88-mile cross-country by Daisy (Surrey and I.C. Club's well-known T.21B) during April, from the home aerodrome to Cambridge—via London Airport. A recent arrival is the T-31, which has now been named Pansy. The Army Club's Tiger Moth is now available for aero- tows during a six-month season—at 15s for 2,000ft.
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