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Aviation History
1919
1919 - 0913.PDF
JULY IO, 1919 DESIGN AND CONSTRUCTION OF FLYING BOATS By Captain DAVID NICOLSON (Concluded from page 876.) Construction. Types P. and N. GENERALLY the hulljconstruction of the P. and N. types consists of a number of stringers disposed, as in Fig. 10, around the more or less circular section of the boat. Stringers.—The longitudinal stringers A, Fig. 10, are of spruce 2J ins. moulded amidships tapering to 1 in. forward and I in. aft, all sided T\ in. At the top and bottom of each stringer are glued a pair of fillets, one on either side of each stringer, to take the fastenings through the floors and the elm moulded ij ins. and sided 3 ins. at amidships and tapered at the ends. It is in one piece, and runs up to form the stem, and is a great improvement on the construction adopted in the F. type. Keelson.—The keelson is of spruce, 5 ins. moulded at amid ships and tapered to stem, and to 2 ins. at the after end. It skin. The writer suggests that I-shaped stringers should be worked out of the solid, forming a lighter and stronger girder. The stringers are secured to the interior bent-wood hoops B of rock elm, extending in planes transversely to the longi tudinal axis throughout the length of the boat, Figs. 10 and II. The hoops are doubled in wake of the wing-root spars, and alternately, scarphed at the top and bottom. Externally around the longitudinal stringers are a number of bent-wood ribs or timbers of rock elm moulded Tss in., sided f in., and >7 B is sided £ in. parallel throughout. The bottom is carefully joggled over the floors, and glued and secured to the keel by two spruce fillets glued and through fastened to the keelson, keel, and floors. The top side of the keelson is rabbeted into the under side of a top member or flange, which is secured by glue and screws. This top member or flange is of spruce moulded J in. at the centre and tapering to f in., sided 2J ins. at the centre, tapering to stem forward and to \\ ins. aft; the keel, keelson, and top member forms a very strong I girder. The sternpost is of mahogany 3 ins. moulded and sided, and extends to 1 ft. above the hull. Saddle straps of elm are fitted, as shown on Fig. 11 ; those at the main spars and tail- plane struts are in one piece running round the boat with their ends fastened to the keel, as in the case of ordinary timbers, and of the same thickness. In addition, doublings of English elm are fitted at the wing-root stay plates at the front and rear spars ; these are clearly seen in Fig. 12. These doublings are carried in a fore and aft direction for a length of 30 ins., and are carefully joggled over the timbers and floors. The planking of Honduras mahogany is fitted in narrow widths with close seams. The inner skin A in. thick being laid diagonally, while the outer skin, A, in. thick, of the same material, is laid fore and aft. Varnished nainsook is laid between the skins ; this not only makes a watertight job, but adds to the strength of the stem chine. The inner diagonal skin is held in position with copper pins, the outer being through fastened to the timbers with copper nails, the ends of which are turned on the face of the timbers. Outside the main structure already described, a double- bottom or water-planing surface is fitted, and known as the step. The water-planes are framed up forward of the main step with three-ply birch and small stiffeners, the frames being spaced 18 ins. apart, and secured to the inner hull planing- bottom with spruce fillets. Chine.—The chine of rock elm is in one piece, and tapered from \\ ins. by \\ ins. at the front step to 1 \ ins. by 1 in. at the stem. The stringers are of spruce, all in one piece fore and aft, fitted through the three-ply frames, which are fixed to the stringers by small fillets. The timbers of rock B a spaced 2 ins. apart, except at the bow, where they are fitted as cant timbers and spaced i\ ins. apart. All timbers are in one piece, bent right round the hull with the ends at the keel, into which they are joggled and glued to the stringers. Floor-timbers.—-The bent floor-timbers are of rock elm f in. moulded, sided | in. at the centre of the keel, and tapered to £ in. moulded and f in. sided at the ends, all embracing one-quarter of the hull, thus ensuring perfect transverse continuity of strength in the timbers. The keel is of rock elm of the same size and spacing as in the main hull, with the ends joggled into the chines, are tapered to fit the hull; they are secured to the face of the stringers with glue and light copper pins. The bottom is planked with a double skin of mahogany with varnished fabric between, similar to the main hull. Fin top.—The fin top is framed with rock elm timbers spaced 2 ins. apart, the ends being joggled into the chines and into a fillet of rock elm. The whole is planked in a similar manner 9T5.
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