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Aviation History
1921
1921 - 0248.PDF
constructors made in the fastenings, as for instance in some •;. / of the F. 3 boats there were only about 60 rivets per square foot; but I am of the opinion Beardmore have overdone the fastening, as they have about 160 rivets per square foot in the skin. The framing in way of the step is of wood, and consists of eight J-in. elm fore and aft formers and 23 |-in. by f-in. rock ELII. Cuing. BLOCK. CHANNELS PET /ML J c. Sketch 5. elm transverse formers each side of centre line, with finishing transverse former at rear end of step fj in. by £ in. rock elm. The step is open to the sea, no attempt having been made meantime to provide watertightness. Six 2 f-in. diameter vent holes spaced 15 ins. centres are provided on the bottom of the hull, just aft of the step, to ventilate same. These vent holes are led into a common pipe, one on each side, and led out from skin about 15 ins. above the load water-line. Watertightness is provided where the vent pipes go through the hull bottom by rubber rings and dished washer plates, the end of the pipe being spun over on the outside. The sternpost is of duralumin 2 ins. by 1 in. solid in section faced on each side by elm blocks, to make up the line of hull. From the sternpost forward 1 ft. 10 ins., in the centre of the boat, duralumin plating is fitted from keel to top, reinforced with duralumin channels to provide for landing shocks in way of rear skid. The engine-bearers are built of duralumin channels and plates, and are placed on the main fore and aft bottom longitudinals to distribute the load over the hull. There are three watertight bulkheads fitted in the length of the boat. A hand-winding anchor gearis provided in the nose, the cable being led through the fore foot; the structure being suitably reinforced in the vicinity and a watertight cable guide provided. In order to prevent corrosion, the whole of the duralumin framework is coated with oleo resin asphaltum varnish, this being done during construction in order that all joints are well protected. Inside the boat, in way of the engine room, there is an additional two coats of paint composed of graphite and tung oil varnish. The whole structure is enormously strong, in fact too strong for the work it has to perform, with the result that the hull is much too heavy. The framework is so rigid that the boat could at any time be completely replanked without distortion to the shape of the general lines. This boat has not yet been tested, but I am afraid the rigidity of the hull Will prove to be one of the weak points in the design. The details and general workmanship are very good, and show a great improvement on many of the service boats. Supermarine Four-Seater - The construction is such that the hull is capable of resilient distortion, so that when alighting on the water or when subject to other forces the hull can spring, thereby materially reducing the effect of the shock. The cross section is egg-shaped, being very light, and yet possesses great strength. The hull APRIL 7, 1921 is built up of longitudinal stringers, with bent hoop timbers inside and light frames outside the stringers, with double plank- ing outside the light frames, all these being through-fastened together. The stringers are recessed to take the light frames, thus giving a good faying surface for the skin. The keelson constitutes a stringer, as it is of similar section. One of the principal features of this design is that no web frames or cross-bracings are required. The hull is a continuous structure, so that the steps are built on to the skin planking. The top of step is connected to a longitudinal fin member, while the bottom is secured directly by small timbers to the hull. "The fins are supported inside by thwartship cross members, small bulkheads and longitudinal members, to give the requisite strength for this member. As many of the sections are of similar design and construction, this lends itself to quick production. All the stringers can be run out in the mill, also the timbers, thus a fair percentage of the work can be executed in running lengths, this being a great improvement on the construction of the " F." type, with so many different sections and details which require to be done by hand. If these boats are being built in numbers, all the planking can be cut in pairs. The diagonal planking being parallel and of equal thickness, can, together with the stringers, timbers, etc., be made stock sizes and issued out in lengths from the store. As a commercial and production proposition the following are the outstanding features :—The reduction of raw material to mahogany, rock elm and spruce, brasswood screws, copper nails and rooves, fabric, marine glue, black varnish and boat varnish, the first of which can be converted into J-in. planking of convenient lengths and widths \ in. by J in., $ in. by f in.), or J in. by J in. rock elm timbers into suitable lengths, stringers of spruce into suitable lengths, and be issued out on the job as required or in suitable quantities for the construction of each hull. Take a hull of 35 ft. in length. You can employ one class of labour only—for instance, boatbuilders ; a small number of men and boys can be placed on this job, and if piece-worked, with the exception of supervision and inspection, the chances of hold-up through materials are BO small, owing to there being no complication, that they can carry straight through and finish their job. Compare this, for example, with a flying boat of the F.3 or F.5 type. You have to start criticising this at the ordinary commercial proposition, in the first instance, of storekeeping. You run into such items as turn- buckles, bolts and nuts, wires, cables, sheet steel, steel tubing, in fact a hundred and one parts that go to the building of a large aeroplane's fuselage. You must employ not one trade but quite a number, such as boatbuilders, carpenters, sheet metal workers, fitters, machine hands, wiremen, riggers, and are immediately in the midst of demarcation troubles, allocation and arrangement of working squads, processing in a dozen different ways ; your inspection costs j;o up in many details, all of which are liable to hold up the job—even a small point if turned down in inspection can completely stop the job for days on end—and if the question of finished stores is not a highly organised one, a small bolt and nut, Wiring plate, etc., going adrift means a stoppage. Stoppage means money, and invariably these stoppages occur which, apart from their own cost, lower the moral of the particular men who are working for completion on the job. Without going into further detail, the foregoing, I think, points out the advantages and dis- advantages of the two types from a construction point of view both from ease of construction, expense and on-costs. During the recent year the Supermarine Company have patented a flexible bulkhead. Owing to the work of the hulls when in any kind of sea-way, it is impossible to make rigid fastenings to the hull: in fact, if this is done the object of the flexible hull is at once destroyed, and if heavily strained the same experience is found in light racing launches ; the hull, although not breaking at the bulkhead, throws itself out or splits several feet away either in a forward or aft direction. If it is therefore desirable to bulkhead a resilient hull, this must be of a flexible nature. After considerable experiments had been carried out a suit- able type was used with every success, its nature being of double diagonal planking, in between and round the edges of which was fitted heavy canvas, marine glued and through- fastened. Where this is to be fastened to the hull an inside timber or hoop is laid round the stringers and through- fastened to the stringers ; a padding piece is laid between the hoop, stringer, and the skin, also through-fastened, forming complete register round the hull. The bulkhead, complete with canvas collar, is then laid in the hull, the canvas necking assuming a " Z " shape in section on either side of the bulk- head. The bulkhead is then secured by floating cross members which allow the whole of the bulkhead to float in any direction or the hull to move in any direction round the bulkhead to an extent of about 2 ins. on any diameter. The arrangements 348
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