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Rh The flotilla leaders, with a deep load displacement of about 2,000 tons and an armament of five 4-in. or 4'7-in. guns, and with their very high speed, might well be described as fast scouts or third- class cruisers.

Patrol Boats (Table V. and fig. 25). Patrol boats were specially designed to relieve the T.B.D.'s of some of their duties such as patrolling, submarine-hunting and escort work, for which high speed was not a necessity. They had to be as small as possible, consistent with keeping the sea in all weathers, with sufficient speed to run down submarines, besides having shallow draught and all top hamper kept low to prevent their being seen at a distance. Economy of fuel was also an important feature, and it was desirable to have them built of mild steel rather than high-tensile steel, in order to simplify the construction. Some were provided with a special hard steel ram, with which a considerable number of ene_my submarines were sunk. The various features were combined in a vessel of something under 600 tons, with geared turbine engines of 3,800 H.P., giving a speed of over 22 knots, with 330 revolutions of the propellers. The boats had large rudder area and were cut up aft, so that they could turn very quickly upon the enemy a most important feature for ramming purposes. They proved very valuable boats

FIG. 19.

on service and did a great deal of work against the submarines in all weathers. They were armed with only one 4-in. gun, mounted in a commanding position on the forward superstructure, one 2-pdr. and two 14-in. torpedo tubes, and later it was arranged to carry depth charges. Their cost was, of course, considerably less than that of a modern destroyer.

Some of these boats were afterwards disguised to look like small mercantile craft a device which also proved quite successful.

Sloops and Mine-Sweepers. On the outbreak of war it became clear that there would be a great demand for mine-sweeping vessels. A good many coasting and cross-channel steamers were taken up for this purpose, but more were required, and it was decided in Dec. 1914 to build twelve single screw ships (fig. 26) of simple design to this end. With the view of hastening construction, it was decided to adopt mercantile practice as far as possible in both hull and machinery. The vessels, although of very fine form, were built of simple construction and under Lloyd's survey. The boilers were of ordinary Scotch type, and single screw machinery was provided.

CD

Liter Vessels have 4-4-7' Gun

FIG. 21.

in lieu of4t4Gun

In the end nearly 100 of these vessels were built, and the arma- ment, which at first was two 12-pdrs., was subsequently increased to two 4-in. or two 4-7-in. guns. A great many of these vessels were built in about six months from the order, and the first 36 averaged 25 weeks in building. They proved excellent sea boats, and were used not only for mine-sweeping, but also for submarine work and for convoying. At later stages some of these vessels were disguised as ordinary merchant ships. They were economical steamers, and were able to attain a full speed of 17 knots, with a H.P. of about 1, 800 to 2,000 in the earlier, which was increased to 2,500 in the later, vessels.

Several of the vessels were mined, but although the damage they sustained was very severe, they kept afloat and were repaired.

The Admiralty was asked to design and provide some vessels of this type for the French Government, and eight of these were designed by Sir E. d'Eyncourt and built for that purpose and armed

with somewhat heavier armament than our own ships. The French Government were very satisfied with the vessels.

In addition to this, at a later stage, for sweeping in shallow water, some paddle mine-sweepers were designed at the Admiralty. These were 15-knot boats, with draught just under 6 ft. 9 inches. They did good work, but were of course not such good sea boats as the sloops. As there was some danger of mines getting under the pad- dles, a further design of twin-screw mine-sweepers was got out. These were vessels of about 800 tons and about 16 knots speed.

Submarines (Table V. and figs. 27, 28 and 29). During the war the design of submarines was enormously developed. A very large number of these vessels were added to the British Fleet. There were some twelve different types, some embodying very special requirements and all being improvements on their predecessors. The Admiralty produced the fastest internal-combustion engined submarine in "J" class, which attained a speed of over 19 knots. As a still higher speed was wanted for fleet work, the " K " boats were designed with a surface speed of 24 knots. To arrive at this it was necessary to go to steam, and special arrangements had to be made for shutting down watertight the funnels, etc. However, all these difficulties were overcome.

It is an interesting point about these vessels that, besides the steam turbines for full speed on the surface and the electric drive when under water, they were provided with a Diesel engine for use just before diving or immediately after breaking surface, in order to quicken diving or getting away after coming up.

Although the Germans had the advantage of more power per cylinder in their Diesel engines, Great Britain produced submarines, faster and more heavily armed than theirs.

M. I. submarine was a monitor submarine armed with a 12-in. gun; she was an experimental boat, and proved quite successful.

" China Gunboats." For use in Mesopotamia or for river work two classes of so-called " China gunboats " were designed by Messrs. Yarrow. The smaller of these vessels, 120 ft. long and of about loo tons, were constructed in Great Britain in such a way that the parts could be sent out to Abadan, where they were assembled, and the vessels reerected and completed under the supervision of Admiralty officers. Some of the larger boats 230 ft. long and of 645 tons, were completed in England and went out to Mesopotamia, where all of them were of the greatest service in that campaign. Most useful work was also done by motor launches and many other types.

Other Auxiliary Craft and Aircraft Carriers. The Admiralty was called upon to design many other auxiliary craft notably some fast Fleet oilers which were able to carry 5,000 tons of oil and had a speed of 15 knots. There were also designed a great number of special smaller craft for all purposes, and a number of merchant ships were taken over and modified to meet diverse requirements.

The most important modifications were those made to vessels taken over and converted into aircraft-carriers, including " Cam- pania," "Ark," "Royal," " Engadine," "Riviera," etc.; the

Furious " was also altered, and the " Cavendish " (now named " Vindictive ") was converted into an aircraft-carrier. The " Argus" (fig. 30) was originally built as a passenger mail ship of 20 knots, and was taken over and converted into an aircraft-carrier with complete flush deck, the funnels being carried aft in long horizontal ducts, discharging the smoke astern. The " Eagle " was taken for conversion into a large aircraft-carrier with a somewhat different arrangement, with the funnels and all deck erections included on an " island " on one side of the deck. Aircraft-carrying ships are in fact gradually becoming more important for the Fleet.

Altogether during the four years more than 2,000,000 tons were added to the navy, at a cost between 250,000,000 and 300,000,000 sterling, exclusive of modifications to auxiliaries. Reference to the navy estimates shows that the aggregate sum spent during the four years before the war on new construction amounted to approximately 60,000,000. In fact, during the four years 1915-8, more tonnage was built for the British navy than during the previous 25 years.

II. NAVIES OF OTHER COUNTRIES

During the period 1910-20 foreign naval construction of all types generally followed the line of British designs, with one or two important exceptions which must not be overlooked.

The most important departure from the British practice was in respect of the number of guns mounted in the barbettes. Triple- gun mountings for the main armament have been adopted by several nations, viz. France, Italy, Austria, Russia and the United States, while in 1914 the French began the construction of quadruple-gun turrets, but neither these turrets nor the ships for which they were intended have been completed.

The British example in regard to the adoption of turbine ma- chinery for propulsion of the first " Dreadnought " battleship and battle cruisers was not followed by the other nations at once. In some cases, for example, Japan and the United States, sister vessels were built, one having turbine engines and the other reciprocating engines. Finally, however, turbine engines were almost universally adopted, while the United States made a fur-