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first showing the transverse portions of structure, and the second those portions which give longitudinal strength.
The ship is framed on the transverse system with a frame, floor, and reverse frame. Deep frames are fitted at intervals. There is a middle line intercostal keelson with continuous angles at the top and bottom. The engine and boiler bearers are so arranged as to assist materially in providing longitudinal strength
to the structure. Flanging of plates is largely adopted to save the weight of connecting angle bars. The deck is of special importance, as it is severely strained if the ship is subjected to a sagging moment. In this case the deck between the beams is liable to buckle, being of thin plating, and in order to enable it to effectively stand the strains, it is well stiffened by fore-and-aft girders. Deep beams are fitted at intervals.
BEAMS, PILLARS, AND DECKS.
Beams-—The transverse framing we have been considering ends at the upper deck. To complete the transverse structure we have beams connecting the sides of the ship together at the level of the various decks and platforms. Beams not only tie the sides of the ship together, but they form the support to the decks and
platforms. Beams for decks on to which water is likely to come, as the upper and main decks, are made with a round down in order that the water may run to the side scuppers. The amount of this round is 9 in. in a 75-ft. battle-ship, and 6 in. in a 40-ft. cruiser. Beams to the lower protective decks are of the same shape as the deck, usually level at the middle line and sloping down to the sides (see Fig. 12). Beams to the lower platforms and decks are level (see Fig. 19).
Beams in a large ship are spaced every 4 ft. where the frame spacing is 4 ft., and every 3 ft. at the ends of the shipFor a small cruiser the beams are placed on alternate frames, i.e. every 4 ft.
Beams are most commonly formed of angle bulb (c, Fig. 8). Most decks are now covered with steel plating, and the angle bulb is then a convenient beam to use. When, however, a wood deck has to be laid direct on to the beams, as is sometimes the case, it is more desirable to have the tee bulb (d, Fig. 8), in order that the deck bolts may be worked zig-zag, and not in a direct line, as would be the case with the angle bulb. The tee bulb is a convenient form to use for skid beams for supporting the boats. A zed bar (e, Fig. 8) is a convenient form of beam when the flat supported forms the crown of a magazine in which teak lining is fitted. The lining can be bolted to the inner flange of the zed. In recent ships, however, the lining to magazines has been dispensed with, so that this form of beam is not necessary. Angle bars are used as beams to flats in which the greater strength of the angle bulb is not required.
The connection of beams to the transverse frames is of great importance, as this, together with the transverse bulkheads, helps to prevent the racking of the ship due to rolling. To ensure an efficient connection, the beam is connected to the frame either by a beam arm, or a bracket plate. The beam arm is used where a neat appearance is desirable, as below the upper deck. To form the beam arm, the beam is cut at the middle of the
web and the lower part is bent down. A piece of plate is then welded in, giving the form shown in Fig. 33. The bracket is used in places where a neat appearance is not so desirable (Figs. 25 and 30). The usual depth of the beam arm or bracket is two and a half times the depth of the beam, so as to get a good riveted connection to the frame. In the special case of the beam to the middle deck, a bracket is not necessary, as sufficient rivets are obtained through the solid plate frame, which is worked beneath the armour (Fig. 34).
Half-beams and Carlings.—Some beams come in way of openings in the deck, as the engine hatch, ventilators, funnel
casings, etc. In these cases it is necessary to cut the beams; these are then termed half-beams. The inner ends of the halfbeams are connected to a fore-and-aft carling, which extends to the first complete beam at each end of the opening. Fig. 35 shows this arrangement for a small opening for a hatchway. The carling in this case is formed of an angle bulb of the same size as the