Navies of the world

by Edward W. Very

United States Corvette Plymouth.
(Wooden System.)

In France the wooden construction was almost exclusively used until the development of the programme of 1873. Iron was then introduced in the armored hulls, iron sheathed with wood in the first and second rate unarmored ships, and composite construction in the gun-boats of less than 700 tons, leaving the light second-rates and the third-rates to the old wood construction.

In the United States the wood construction is still invariably followed. There are no composite vessels in the navy, nor has any attempt been made to build one. There are two or three iron vessels of 1000 tons displacement, built during the period of greatest demoralization, and on account of political pressure brought to bear in the interest of iron merchant-ship building. These vessels can scarcely be pointed at with pride, since, throughout the naval world, pure iron construction is found only in transports and troop-ships. In England, where iron ship-building had its birth and development, constructors have never proposed this very excellent type of merchant-ship construction for war-vessels.

Wooden Construction.

The keel in the wooden construction is sided to a certain proportion to the beam of the vessel, the pieces composing it being generally connected by a plain scarf, the stem carrying the form up forward being hook-scarfed to the forward end of the keel and supported by the timbers of the deadwood and apron, forming a solid mass at the fore-foot. The stern boundary is carried up in the main stern-post, which seats with two tenons on the after-end of the keel, being supplemented in some vessels by a rudder-post, but generally in the larger classes of vessels the latter gives way to the equipoise rudder. The angle of the stern-post and keel is made up into a solid supporting mass by the after-deadwood. The junction of stern-post and keel is further strengthened by bronze castings bolted on each side. The keel is rabbeted each side to receive the garboard strake of planking, and the stern-post and apron prolong the rabbet at either end for the hooding-ends of the outside planking. The floor-timbers cross the keel, giving an alternate long and short arm on either side, the frames being carried up by futtocks and top-timbers shifting butts. Over the floor-timbers in the plane of the keel a heavy keelson is laid with, generally, sister-keelsons on each side, the system of keel and keelson forming the rigid back-bone of the ship.

The longitudinal supports of the ship are the boiler-keelsons, parallel to the main-keelson and forming the supports to the boilers; the diagonal bracing, composed of iron ribbons of about three fourths of an inch in thickness, crossing each other at an angle of 45°, and forming a complete lattice-work for the ship extending from the spar-deck to the turn of the bilge. These braces are generally worked on the inner side of the frames, but in certain cases they have been worked on the outside or on both sides. The inner planking, formed of the thick strakes, bilge-strakes, and ceiling; the deck-clamps, ranges of heavy plank for the support of the ends of the beams; water-ways, covering the beam-ends and corresponding to the deck-clamps underneath; and the outside planking.

Diagonal Braces.

The transverse supports are the beams with their connecting systems of knees and carlings, the breast-hooks and transoms, and finally the decks themselves, which furnish both longitudinal and transverse support. Of late years it has been the custom to make the beams, knees, breast-hooks, and transoms of iron, and it is a very general idea amongst those who have not paid especial attention to the subject that this modification, taken in conjunction with the introduction of diagonal braces, constitutes composite construction, which is by no means the case. In the wooden construction the American and the English systems are very closely allied, whilst the French differs from both in many details. These differences are, however, in the detail work, a description of which would be scarcely warranted in the general summarizing of a system.

The outside planking is made up of a series of strakes differing in thickness of plank in accordance with the points at which the greatest strains are brought by the motions of the vessel. Next the keel on each side, and tending to give it thorough support, are ranges of plank firmly secured in the rabbet of the keel and thicker than the planking in general, called the garboard strakes. Outside of the gun-deck beams is another range of heavy planking called the main wales, and in two and three decked vessels other strakes called middle wales are worked abreast the other beams. In the same way a great longitudinal strengthening is gained in the deck-planking by the outer range of planks next to the water-ways, called the thick strakes.