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).

INNER BOTTOM

3x3

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. (16 in.), with a single angle along the bottom 3 in. x 3 in., and a single angle along the top 3 in. x 3 in.

171⁄2 Las:

3/4 RIVETS 41⁄2 5 Dia

3. 3/2

FIG. 15.-Watertight longitudinal.

The 31-in. flange is necessary to take the 7-in. rivets used for the 25-lb. (3 in.) outer bottom, 2-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

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,

V. KEEL

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 of 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

upwards, and under the heavy weights of the barbettes and the engines. The third class is fitted under the main transverse bulkheads (the inner bottom being continuous), and at intervals between (see Fig. 52). The bracket frames are fitted to the remainder. In one ship out of a total of 780, 456 were solid, 180 were watertight, and 144 were bracket frames.

The bracket frame is built up as shown in Fig. 17. Deep angles, 5 in. x 3 in., are worked to the outer and inner bottoms, and to these in each bay are riveted two bracket plates, 15 lbs. (3 in.), with their inner edges stiffened by a 3-in. flange. These are connected to the vertical keel and longitudinals by pieces of angle 3 in. x 3 in.

The plate frame (Fig. 17) consists of a 15-lb. plate connected to the inner bottom, vertical keel, etc., by angles 3 in. x 3 in., and to the outer bottom by angles 3 in. x 3 in. Each plate is stiffened by an angle bar, and holes large enough to enable a man to pass through for inspection purposes are cut to lighten the plate.

The watertight frames (Fig. 17) with the vertical keel and watertight longitudinals divide the double-bottom space into a large number of watertight compartments. The frame is made of 15-lb. (-in.) plating under the transverse bulkheads, and 123 lbs. (in.) in other places. The space is filled in solid with the plate, and staple angles are worked round the top and bottom as shown. This enables a tight fit to be made, and the whole is closely riveted for watertight work and caulked. These frames are specially stiffened, as shown, by three channel bars in the first bay, one channel and two angles in the other bays up to No. 4 longitudinal. This extensive stiffening is fitted to make the framing strong enough to stand the severe strains which exist when such a heavy ship is in dry dock. Recent ships are being fitted with docking keels at the side, as in Fig. 13. In these cases the stiffening of the watertight frames is not so extensive as described above.

Extra frames, both longitudinal and transverse, are worked under the engines in order to provide a rigid support.

Framing behind and above Armour.-The character of the framing behind armour is governed by the necessity of providing a rigid support to the armour. For armour 6 in. and 7 in. thick, the framing is formed of 10-in. zed bars, 24 in. apart, with fore-and-aft stiffening girders. For armour 9 in. thick, a more massive support

is necessary, and the framing is formed of plate frames 15 in. deep, 24 in. apart, with angles on the edges as shown in Fig. 18. There are fore-and-aft girders in addition, as shown. In either case the frames are well supported by bracket plates at the heads and heels.

The framing above the armour, between the main and upper

decks, consists of 6-in. zed bars 4 ft. apart, with 4 in. x 3 in. angles between. In ships with an armoured battery, as Fig. 13, the framing is made stronger to form a support for the armour.

Framing at the Ends of Ship.-The above description refers to the framing over the length of double bottom, or about twothirds the length. The ends of the ship are framed on a somewhat

different principle. Here the longitudinal strength is of less importance, and the main function of the framing is to stiffen the outer bottom plating. Accordingly we find that the transverse framing is continuous either side of the vertical keel to the protective deck, and this framing is more closely spaced, viz. 3 ft.

The vertical keel is still continuous, but not watertight, and the frame consists of a vertical floor-plate with outer and inner angles to the bilge. Above this the frame is formed of a 6-in.

zed bar. In Fig. 19 the top of the floors is covered in with a watertight platform, and the zed bar is passed through with the inner flange cut away. This makes the watertight work at the ship's side more readily performed than if the complete zed bar went through (see Fig. 41).

As before stated, the vertical keel is continuous from end to end of the ship, but the five longitudinals on each side, which extend over the length of double bottom, are altered in character at the ends. They are either twisted round to connect on to a