Submarine

In the United States, John P. Holland, engaged in the study of the problem for many years, built the first of several subma rines in 1875. Other early research was undertaken by Simon Lake who developed the "Lake" type submarine. In 1888 the Navy Department invited submarine designs, that of Holland being selected, but the contract for the "Plunger" to that design was not signed until 1895. She was to be propelled by steam on the surface, and an electric motor submerged, but before com pletion, Holland, dissatisfied with the design, returned the sums advanced by the Government, and started on the "Holland." She was purchased for the U.S. Navy on April II, 1900, five simi lar vessels being ordered to be built. On Dec. 13, 190o, the Brit ish Admiralty ordered five of the same type from Messrs. Vickers, who had obtained the rights to build to the Holland designs. In Italy the "Pullino" of 25 tons designed by a naval engineer of that name was launched in 1892, and was followed by the "Delfino" of 95 tons, launched in 1894. In Germany two sub marines of 200 tons of Nordenfelt design were completed in 1890, but until 1906 the construction of this type of vessel was not seriously taken in hand for that navy.

Types of Hull Construction.

In order to submerge a submarine several tanks designated "main ballast tanks" are completely flooded and a less number of smaller tanks are partly flooded. As these tanks when filled bring the vessel from the surface to the submerged condition, their total volume is the reserve of buoyancy of the submarine when on the surface, and is a measure of her seaworthiness. Submarines are either "single hull" or "double hull." The "Gymnote," "Gustave Zede" and "Holland" were of the first type having a strong hull of circular section throughout, the centres of the circles lying on a straight line, the axis of the submarine. In later examples the circular changes into elliptical sections at the extremities, the centres of the sections rising towards the ends. The main ballast tanks are at the bottom of the circles, and may or may not have vertical extensions at the sides enclosing the battery spaces (fig. r).

The "Narval" of Laubeuf, the first of the double hull type, had a strong hull of almost circular section,—the pressure hull— enclosed by another—the outer hull—of light construction, the space between the two being the ballast tanks (fig. 2). The capacity of the latter was far greater than in the single hull type, being in "Narval" 41 per cent of the displacement as com pared with 13 in the "Holland." The removal of these tanks from inside the pressure hull gives more space in the latter for other purposes. In addition to improved seaworthiness, a better shape for surface propulsion can be given the outer hull and increased speed obtained. When air pressure is used to clear the ballast tanks of water, this pressure is brought on the curved surface of the pressure hull, instead of on the flat plating of the tanks in the single hull type. The pressure on the outer hull, when

blowing, is the small difference between air and sea pressure, per mitting the outer hull to be of light construction. The meta centric height of the single hull type on the surface is small, that of the other type can be made any desired amount by a suitable choice of breadth of the outer hull. The single hull type has the advantage of more rapid submergence, the tanks being smaller and well below the surface water plane, whilst parts of the tanks in the double hull type are above that plane. The double hull type is heavier and costs considerably more to build.

Generally the single hull type of construction is now limited to the smallest submarines, the double hull to the largest. In the medium size a partial double hull is adopted, the outer hull enclosing the pressure hull over a portion of its extent only, both transversely and longitudinally (figs. 4 and 5). Fig. 3 shows the section of pressure hull adopted by Colonel Laurenti of the Fiat Company, the shape being designed to suit the requirements of stowage. Fig. 4 is the section of the British D, E and L classes, the bulk of the ballast water being outside the pressure hull. Fig. 5 is a section of the British K class. In the latest types of "double" and "partial double hull" submarine oil fuel is also stowed between the two hulls. The double hull types are some times termed "submersibles" to indicate they are especially suit able for surface propulsion.

Superstructure.

The "superstructure" is the light structure fitted above the pressure or the external hull, in which are stowed the cable holders, boats, bollards, hatches, mufflers, fairleads and other fittings, and which unless enclosed would cause undue resistance when submerged. The superstructure is fitted with a deck, and is raised in height amidships to form a navigating bridge, which is reached from the control room through the conning tower built up from the pressure hull. The conning tower is fitted with hatches at the bottom and at the bridge level, and being the last portion of the pressure hull to submerge, is fre quently constructed of thick plating to resist projectiles. The conning tower forms a base for the vertical brackets which sup port the periscopes. The sides of the raised superstructure en closing the conning tower and other high openings and forming a support for the bridge is called a conning tower cutwater. The superstructure with the exception of the low buoyancy tanks is "free flooding," i.e., it is flooded and vented when submerging through open holes along its sides, the air escaping through numerous holes in the superstructure deck. The low buoyancy tanks are free flooding, central vented.