CHAPTER III. FRAMING OF VARIOUS TYPES OF SHIPS. THE British Navy, intended to operate in all parts of the world, is necessarily made up of many different types of vessel. It would be obviously impossible in a work of this character to exhaustively describe the construction of each type of vessel in the Navy. All that is possible, or desirable, is to take certain main types, and deal with the principles of their construction. It will be seen that the intended service of a ship has a distinct influence on the construction. First Class Battle-ships.-These ships are heavily armoured and armed, and possess speed which is moderate compared with that obtained by to cruisers. One distinctive feature of the construction of these ships is the provision of an inner skin up the protective deck. Sections of recent battle-ships are shown in Figs. 12 and 13. The inner skin is 3 ft. in at the middle line, the depth being somewhat less up the bilge, and it is continued up to the protective deck in the form of a vertical bulkhead. There is, in addition, the inner coal-bunker bulkhead, so that at the side and bilge, at the lines AA and BB, there are three skins to pierce before a vital portion of the ship is reached; at the bottom there are only two skins to pierce. This arrangement is important, in view of the possibility of being rammed or receiving other damage under water. The double-bottom arrangement is adopted in all ships of the Royal Navy above third class cruisers. A double bottom is valuable as providing an inner skin in the event of damage to the outer bottom, and it is always subdivided into a number of watertight compartments, so as to localize any damage that might occur. A part of the space is conveniently arranged for the stowage of fresh water, forming the boiler reserve feed. Any of the doublebottom compartments, including the wings, can be flooded if desired to correct heel or trim caused by damage (see Chapter IX.). In the Royal Sovereign the protective deck was level, with a thick belt, 8 ft. broad, as shown in Fig. 11. In the more recent ships, the armour belt has been much reduced in thickness and increased in area, and the protective deck has been made level at the middle line, but sloping down to the lower edge of armour at the side (see Figs. 12 and 13). Longitudinal Framing.-The main framing of these ships is arranged on the longitudinal system, the presence of the double bottom lending itself admirably to this arrangement. The foreand-aft framing below protective deck over the length of the double bottom (about two-thirds the length) consists of a vertical keel, 3 ft. deep, and five longitudinal girders on each side (see Fig. 12). Of these the vertical keel, second and fourth longitudinals are watertight, thus dividing the double bottom from side to side into six watertight compartments. The vertical keel and longitudinals are continuous, and the latter are allowed to taper somewhat in depth towards the ends of the double bottom. The vertical keel is 25 lbs. (ğ in.) thick, with two angles along the bottom 4 in. × 4 in., and two along the top 4 in. x 4 in. These, together with the middle plate of the inner bottom, and the inner and outer plates of the flat keel, form a substantial backbone to the ship (see Fig. 3). The adjacent plates of the vertical keel are connected by 30-lb. (in.) treble riveted butt-straps (Fig. 14). Adjacent lengths of the angles at top and bottom are connected by bosom pieces of angle as shown. All the riveting is closely spaced for watertight work. The longitudinals are 17 lbs. (17% in.), with a single angle along the bottom 3 in. x 3 in., and a single angle along the INNER BOTTOM 1/4 RIVETS, .. 7-8 DIAR top 3 in. x 3 in. The 31-in. flange is necessary to take the -in. rivets used for the 25-lb. (3 in.) outer bottom, 3-in. rivets being used elsewhere. The longitudinals are worked in this ship square to the outer bottom, but in a recent ship (Fig. 13) No. 4 is worked horizontal, to form a flat for the wing bunker. The arrangement of riveting depends on whether the longitudinal is watertight or not. The 172 Lo FOR No. 1. NON WATERTIGHT LONGITUDINAL riveting in Nos. 2 and 4 is closely spaced (Fig. 15), and a double-riveted butt-strap is fitted. The connection of the ordinary frames only need the rivets spaced 7 to 8 diameters. Nos. 1, 3, 24 and 5 have lapped butts (Fig. 16), and the riveting is more widely spaced. These longitudinals are lightened with manholes, which, in addition to lightening, serve the very necessary purpose allowing freedom of access throughout the compartment. These non-watertight longitudinals also have holes at the bottom as shown, so that water will readily drain to the pump suctions. Transverse Framing.-The framing running transversely across the ship in the double bottom is worked intercostally, i.e. in short pieces between the longitudinals. Adjacent frames are generally 4 ft. apart. The frames are of three types, (i.) bracket frames, (ii.) solid plate frames lightened, and (iii.) watertight frames. Of these the second type is the most numerous, as it is the type adopted beneath the armour from No. 4 longitudinal |