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Aviation History
1932
1932 - 0168.PDF
FLIGHT, FEBRUARY 19, 1932 out the world by J. W. Gates & Co., Ltd., 133, Oxford Street, London. W.J. In the development of metal con struction, linen aeroplane fabric has not been eclipsed by metal sheeting for covering wings and fuselages. Metal sheeting and linen fabric both have their advantages, but one can assume that as long as British air craft designers favour the biplane over the monoplane, fabric will hold favour as the covering material. Fabric scores in its lightness, its cheapness, and ease of repair. It also renders periodical inspection of the internal structure more convenient. Quality and Manufacture For aircraft purposes the fabric must be made of fine long flax fibre, dew- or water-wetted, and the yarns must be spun wet. Before the yarns are boiled they must have leas and twists of the following values: — Tolerance Twists (turns Yans Leas on Leas per inch) Warp ... 85 ±5 16 to 18 Weft ... 100 +10 17 to 20 The weight of the yarn on boiling must be reduced 7£ to 12\ per cent. A plain weave is necessary and the fabric must be uniform and as free as pos sible from slubs, snarls, knots, loose ends and other defects of preparation, spinning, weaving and finishing. The selvedges, which are the edges of the fabric, are woven so that they do not unravel. After weaving the fabric is beetled, and a specimen is tested for beetling in the following manner. It is secured over one side of a strong rectangular frame, 10 in. by 10 in., so that it is stretched under a tension load of 2 lb. per in. warp and 2 lb. per in. weft, both warp and weft being parallel to the sides of the frame. Five coats of cellulose acetate dope are then applied to produce an increase in weight of 2 oz. per sq. yd. The first coat has to dry in not more than 1 hr., and show no wet translucent patches or bubbles at the end of that period. Each of the remaining four coats must dry in half-an-hour. Finally, the completely doped fabric specimen must show a uniform sur face, free of discoloured patches and bubbles. It must also, at this junc ture, conform to a specified degree of tautness. Size-Softening Agent Test A test of the size-softening agent or lubricant chosen for the purpose of dressing the warp in the fabric has to be made by the following method. The agent must be tallow, palm oil or Japan wax, free from paraffin wax and other added unsaponifiable matter. The selected sample must be melted in a dish to render it homogeneous and then 0.1 gramme is mixed with 10 cc. of cellulose acetate dope and allowed to stand until all the air bubbles have risen. Next it is transferred to a petrie dish, an equal volume of dope is poured into another petrie dish, and the time taken for the contents of each dish to evaporate is noted. If the dope containing the size-softening agent produces a film containing air bubbles or takes appreciably longer to evaporate the size-softening agent must not be used. Strength Test The fabric is manufactured to a width of 36 in., upon which an allow ance of plus or minus \ in. is per mitted- Its weight, including the normal regain (12 per cent.), has not to exceed 4 oz. per sq. yd. The strength factor required is a breaking load of not less than 90 lb. per in. width of warp and weft and the strength test is conducted as follows: From each roll of fabric manufactured 12 specimens are cut, six in the direc tion of the warp and six in that of the weft. Each specimen is 2|- in. wide with its end threads frayed out from each side to reduce the width to 2 in. A specimen is soaked in water for half-an-hour, wrung out and then placed as quickly as possible between the jaws of the testing machine so that the unstretched length is not less than 7 in. The load is then applied at the rate of 180 lb. per min. It is possible to appreciate the large quantity of aeroplane fabric in demand from the fact that a light aeroplane requires 100 sq. yd., while a large machine like the de Havilland " Hercules " wants clothing with 750 sq. yd. AERODROME CONSTRUCTION AERODROMES are a specialised business, and their construction and maintenance requires considerable knowledge not possessed by the aver age type of man who is otherwise competent to level and drain tracks of land. When the '" En-Tout-Cas " Co. (Syston), Ltd., enlarged then- landscape department to cope with aerodrome work, Mr. R. H. S. Brown first of all toured all the principal aerodromes and landing grounds of Europe by air and then made an ex tensive trip in America and Canada in order to gain, at first hand, as much knowledge of the subject as possible. Mr. Brown also learnt to fly himself, in order that he might better appre ciate the difficulties from the flying point of view (incidentally he is one of the hard-working secretaries of the Leicestershire Aero Club), so it may confidently be said that the En-Tout- Cas Co. is peculiarly competent to undertake constructional work in con nection with aerodromes. The side with which they have had consider able success is the building depart ment, which deals with the construc tion of hangars and clubhouses. They have erected hangars on the aerodrome of Ratclifle belonging to Mr. W. Lindsay Everard and also converted two farm cottages on the aerodrome, making them suitable for housing the pilot-in-charge. Early last year a large clubhouse was de signed for Phillips & Powis, Ltd., at Reading aerodrome, and this was completely erected ready for occupa tion in the short space of 13 weeks. This somewhat palatial building was described in FLIGHT for May 22, 1931. At Heston a tea verandah for the public was erected to the design of Mr. Graham Dawbarn and was also completed in very quick time. A further development showing the go- ahead policy of this company is their provision for extended payment schemes in connection with club houses, hangars and aerodrome work done for flying clubs. This is an ad mirable idea, for it is certain that many flying clubs are unable to pro vide large sums, and the provision of such arrangements for their benefit must undoubtedly result in further work for the Company, and with this end in view they are prepared to ex tend the scheme to any flying club or any approved person connected with the aviation business in Great Britain. AERONAUTICAL SEAMSTRESSES : A corner of the D.H. shops showing girls covering aeroplane fuselages with fabric. 160 .
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