Practical Shipbuilding

In larger warships—battleships and battlecruisers—the system of construction does not differ in principle from that described above for a cruiser. The thickness of plating is greater and the scantlings in general are heavier ; and there are several decks which are supported by pillaring (or bulkheads), extending down from deck to deck to the inner bottom where the loads are finally bal anced by the water pressure transmitted through the framing. The armour instead of forming a portion of the structure (as in the cruiser shown) consists of separate hard plates bolted to the ship's side, which is recessed for the purpose ; the framing beneath is frequently strengthened in order to support the heavy localized weight. In other respects the structure of a battleship and that of a cruiser are generally similar.

Destroyer.

The destroyer construction is different from that of a cruiser, for there is no double bottom and the important fram ing is worked transversely and closely spaced (about 21 inches). Owing to the disproportionate weight of machinery which these vessels have to carry, the lower part of the framing is adapted to form supports to the boilers and engines ; in the ship illustrated the ordinary frames are interrupted and replaced near the middle line by heavy floor plates. Deepened or "web" frames are worked at intervals in order to provide adequate transverse strength and stiffness. Each frame is connected to a beam supporting the deck above.

The longitudinal frames, which are generally slotted over the transverses, are few in number ; but they render valuable assistance to the general as well as the local strength by stiffening the thin plating in their vicinity and preventing it from buckling under a compressive load. They are of particular importance under the deck where they form an integral and valuable portion of the struc ture which would otherwise be too severely stressed in a seaway. The thickness of the shell plating amidships is in places as small as 0.17 inch; together with the deck, vertical keel and all parts contributing to the longitudinal strength it is made of special quality steel capable of withstanding high stress without injury.

Sloop.

The structure of this well-known type of naval auxil iary craft generally resembles that of a light mercantile ship. The framing is transverse and closely spaced (21 inches). The thick ness of the shell plating is about a inch.

Submarine.

The structure of an "L" class submarine is de signed primarily to resist the water pressure when submerged. Except for the vertical keel and the local supports to machinery, the framing is therefore wholly transverse and is fitted in the form of rings spaced about 21 inches apart. The thickness of the main

hull plating is about 1. inch, and that of the ballast tanks a inch. The transverse strength is supplemented by the bulkheads fitted at intervals.

Watertight Subdivision.

An efficient system of watertight subdivision is particularly important in all classes of warships; for without it any degree of damage below the waterline would lead to the withdrawal of a ship from action, if not to its ultimate loss. In arranging the subdivision it is necessary to localize the influx of water due to small damage, e.g., perforation by fragments of bursting shell, as well as to provide against large damage due to running aground, or being struck by a torpedo or mine. For this reason fairly minute subdivision is required ; the main trans verse bulkheads (which in merchant ships constitute the whole, or nearly the whole, of the watertight partitions below the "free board deck") are supplemented in warships by minor transverse and longitudinal watertight bulkheads; moreover in general, every deck and flat is made watertight. By these means the buoyancy, as well as the stability of the ship is preserved ; and if due care has been taken to maintain the watertightness of the various bulkheads, etc., a warship should be able to continue in action after being holed in a large number of places.

It may happen that the injury to the ship, although insufficient to sink her, may lead to a large heel or trim, which would prevent the ship being manoeuvred in action or her guns being fired. To remedy this, means are provided for correcting heel and trim by flooding compartments on the opposite side or end of the ship; suitable compartments are selected for this purpose, and large valves fitted so that the spaces may be quickly flooded when de sired. Information is also supplied to the commanding officer on the effect of flooding each compartment, so as to enable a rapid decision to be made in emergency as to any flooding that may be desirable. An important feature of the subdivision of war ships is that the main transverse bulkheads are made as far as practicable intact. They are not pierced by doors or any other fittings except the necessary electric leads and power pipes, which are placed as high as possible, and, whenever it can be arranged, above the waterline.

Ventilation.

The fittings of warships include those used in direct connection with the armament of the ship (see also ORD