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Aviation History
1919
1919 - 0875.PDF
JULY 3, 1019 together with copper nails, and to the floors and stringers with brass screws. Along the keel and fin member it is con nected with brass screws 11 ins. apart. In the earlier types of boats the planking was 5 ins. in breadth, with the rivets widely spaced, but it was found that withj^his breadth the atmosphere affected such thin material, aadjopening of the seams resulted. The planking was after wards cut down to 3 ins. in breadth. It was also found necessary to keep the rivets very close to the edge of the planks, as there was a tendency for the planks to buckle. The bottom planking extends to the fin chine, which runs from the bow for fully two-thirds of the length of the boat. Figs. 5 and 6 illustrate the connection of the planking with the fin chine in the earlier and later types of boats, and it will be seen that the back rabbet for the planking of the fin top and fin bottom is more workmanlike in the former than in the latter, which is less than 1 in. in length. By having only in. of material between the ends of the fin chine and the planking, a boarding boat coming alongside might cause the planking to spring, as such a meagre allowance is inadequate to prevent an accident of this kind. Fin Top.—The timbers under the fin for the early F.3 hulls were heavy and widely spaced, but in later boats timbers iin. by T6tin., spaced 2 ins. apart, were substituted to permit all-through fastenings of the diagonal planking on the hard wood timbers. It might also be stated here that the fin FIN CHINE • F 3. top of the first series of F. boats was of three-ply birch, and in later types was covered with fabric and varnished. The introduction of diagonal planking was a great improvement on this system. All the fins on the F.3 class are flat, but the F.5 types have a J-in. camber, which adds to the strength, gives a better appearance, and assists in getting rid of water easily. Stringers.—Two stringers, equally spaced from the fin member, run under the fin, and other,two stringers placed immediately below these on the bottom are connected by J-in. square posts spaced 1 ft. apart. Intermediate stringers, 16 ft. long, are introduced in the fore part of the boat further to strengthen the shell and to absorb shocks when the hull alights in the water. Fin Member.—In the first boats of the F. type the fin member, Fig. 7, was of American rock elm. On account of improper connection between the side of the hull and the fin top, the longitudinal seam naturally opened up, so in later hulls the fin member was constructed as in Fig. 8, which has the member and bead in one. This in turn might be improved by rabeting out a piece at the back to allow the sides to house correctly, as in Fig. 9. Bow and Nose.—The timbering at the bow is composed of rock elm, J in. by § in., spaced 2j-in. centres apart, and reinforced by horizontal stiffeners below the top longerons. These are spaced to take the outer seams of planking, tapered towards the stem, and connected to the same by small oak breasthooks. These breasthooks bind the two sides of the bow together at the juncture of the stringer and stem, thus forming a very strong combination. Above the top longeron there are 10 deck-stringers, which are notched to take the ribs, together with three strong beams which subdivide the athwartship ribs. This skeleton, which is shaped like a dome, is planked diagonally, the inner skin being laid at 45 °, with the forward ends of the planks lowermost. The outer skin is laid approximately fore and aft to suit the curve of nose. Each skin is of mahogany, ^\ in. thick, the planking being fastened to strong beams with wood screws. Where stringers and ribs occur, copper nails are driven through and fastened on rooves on the inner skin ; elsewhere the planks are fastened with copper nails spaced about 1 in. apart. This work, being well constructed, adds greatly to the appear ance of the boat, and although the bow is slightly heavier than the rest of the hull, it is the best piece of construction in the whole boat. Strength at the nose or fore end of struc ture is very essential, for at high speeds the resistance of the air is very great at this point, and a weak nose would be very easily damaged and driven in. Sides.—Abaft the bow planking, the sides are of three-ply birch, and extend from the bottom of the fin member to the top longeron, running aft to the gun-port openings, a distance of about 18 ft. The three-ply boards are butted against the side stanchions, thus saving buttstraps. Up to within a few months ago, the sides abaft the gun-port openings were built up of a narrow strip of mahogany, with fabric stretched between the same and the upper longeron. The fabric was not strong enough in anything like rough weather, nor under bad handling in fine weather, and the tails were weak in tor sion ; it was therefore superseded by diagonal planking of two skins, each T's in. thick, with nainsook between. This planking was fastened to timbers, running from longeron to longeron, spaced 2 ins. apart, with one stringer midway running fore and aft. The new tail planking was a great improvement, although it added about 47 lbs. to the weight of the hull; but experience has justified the change and extra cost. Several of the latest hulls have the sides covered with *75
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