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450 field. On the deck, well protected by deckhouses, are four lines of rails, which will take 54 lO-ton wagons. Heavy guns and heavy machinery of all description were transported by these vessels.

Some of the most remarkable vessels in the world are the Sound and Lake steamers of the United States. Recent vessels on the Lakes are the largest paddle steamers ever built, such as the " City of Cleveland III." (1907), 4,568 tons and 19 knots speed; " City of Detroit III." (1912), 6,061 tons and 20 knots speed; and " Seand- bee " (1912), 6,381 tons, 19! knots. This last remarkable vessel is 484-5 ft. x 58-1 ft. x 24-0 ft. To drive her paddle wheels she is fitted with compound, three cylinder engines; cylinders being, one 66 in. in diameter, and two 96 in. in diameter, with a stroke of 9 feet.

Developments in Shipbuilding. The greatest innovations during 1910-20 were in connexion with rapid shipbuilding during the war. The production of " standard ships " in Great Britain has been already referred to. Six types were " standardized " (see Carter I.N.A., 1918, and, for detailed summary with dimensions, Ship- builder, May 1918).

Others were approved at a later date, and permission to build large numbers of such ships was given to various shipbuilders. In these ships special methods were adopted to reduce risk of sub- marine attack, such as improved sub-division, making both ends alike, with bridge, poop and forecastle ends rounded, funnels and masts symmetrical in profile elevation with regard to a vertical line amidships, but not on the fore and aft centre line so as to increase difficulty of detecting speed and course of vessel. Very greatly improved accommodation for ship's company was also provided.

The best method of expediting the building of merchant ships occupied many minds, and proposals were made by Sir Eustace d'Eyncourt in 1917 to simplify the construction of war-time vessels by making all frame-lines straight, and the plating so far as practi- cable of developable surfaces. A successful design was proposed on this basis, and adopted by the Controller of Merchant Shipbuilding for use in the fabricated ships about to be built at the National Ship- yards on the Severn. The first fabricated " straight line ship," the S.S. " War Climax," was completed at Wallsend by Swan, Hunter& Co., on Sept. 28 1918, 31 weeks from laying keel.

In Great Britain large numbers of vessels of standard designs were built by various shipbuilders according to their usual routine. The " fabricated " ship followed later. In the United States, however, the standard ships were mostly fabricated ships also. The first series were produced by the Submarine Boat Corporation in new premises at Newark Bay. The most wonderful of all the American shipyards was, however, at Hog's I., Philadelphia, which in less than 12 months passed from open 50 ft. ground to the greatest shipyard in the world, with full equipment and deep water jetties. The con- tract was signed on Sept. 13 1917, and work started Sept. 20. The first keel (S.S. " Quistconck ") was laid Feb. 12 1918, launched Aug. 5 1918, and by Jan. 8 1919, 16 vessels had been launched and 7 completed, 50 slips had been built and 7 jetties, 1,000 ft. long and too ft. wide for fitting out afloat. By April 17 1920, 102 ships of 800,000 tons d.w. had been launched and 84 of 657,000 tons com- pleted. The fabricated parts were prepared in 90 engineering works from 10 to 1,500 m. away.

Ferro-Concrcte Ships. For many years small vessels had been built of reinforced concrete in localities where steel and the special labour required for steel shipbuilding was not available. Such ves- sels had been built in Italy, Norway and France. Between 1887 and 1917 some 200 craft had been built, but in the latter year the subject was more seriously considered, and craft of increasing size were built, and greater numbers of them fitted with propelling machinery. In England 1,000 ton barges, tugs of 750 h.p,, and cargo steamers of 1,150 tons d.w. were built. The first steamship, " Armistice," was built at Barrow, and was reported to run well and cost very much less than a steel ship for upkeep. In Great Britain most of the concrete vessels were tow barges, but in a number of cases steam or oil engines were fitted. Cargo boats 1,150 tons d.w. 205 ft. x 32 ft. with engines of 350 I. H.P. for 7^ knots, and tugs 125 ft. x 27 ft. 6 in. with engines of 750 I. H.P. were built. In the United States very much larger vessels were built as experience was gained. The S.S. "Faith" was 320 ft. x 44-5 ft. x 30 ft. d.w. 3>95 tons on 22 ft. 6 in. draught, triple expansion engine of 1, 600 I.H.P. were fitted giving loj knots speed. Others were built of 3,000, 3,500 and 7,500 tons d.w. as well as eight oil tankers of 7,500 d.w. The Emergency Fleet Corporation ordered 56 ships of an aggregate d.w. of 300,000 tons, besides 34 barges and lighters.

Welded Ships. The Oxy-Acetylene process, for cutting out dam- aged portions of ships and machinery, and for welding in portions in the course of repair, has been of great service, particularly for the repairs of large forgings, castings and boilers. To a less extent the "Thermit " process has been used for welding purposes, but its application has been of a comparatively limited character. During recent years very considerable progress has been made in develop- ing systems of electric welding, which were used to carry out repair work of considerable magnitude during the war. It has also been proposed that the complete ship should be welded, thus avoiding a great portion of the labour and expense of riveting. Several sys- tems have been developed which can be operated in the ordinary shipyard^ and considerable progress has been made in Sweden, England, the United States and France. In 1915 a small vessel

was built by Geary at Ashtabula Harbour, Ohio. This vessel was 42 ft. long, II ft. beam and 6 ft. 6 in. draught, and the welding was carried out with bare metallic electrodes. Two vessels of 52 to 62 ft. in length have also been built, one in France in 1919 and one in 1920 in Sweden " Esab IV." In each case the welding was carried out by the Kjellberg process, and each of these craft is propelled by semi- Diesel crude oil engines, which can also be used to provide electric power for welding, and compressed air for use in carrying out the repairs of ships by this process as they float in harbour. In this process the arc is also used, but a fireproof sleeve of non-conducting material projects over the arc so as to shield the molten metal from oxidization. A boiler 15 ft. 6 in. in diameter, known as the Haw- thprn-Wyber boiler, has been successfully constructed by means of this process. The process of the General Electric Co. is quite differ- ent; in this case metallic contact takes place, the welding material is raised to the necessary temperature by resistance to the passage of the current, and it is at the same time pressed into place by hydraulic pressure. A 46-ft. section of a 9,600 ton vessel being built in New Jer- sey has been used to test the practicability of this, and other methods, and it is reported that these experiments show a saving of 60 % on labour and 15% on material, as compared with riveted work.

During the war a steel barge, 120 ft. by 16 ft. and 275 tons dis 1 - placement, was built at Richborough, Kent, in order to test to what extent labour could be saved. Here the Quasi-Arc process was used and the vessel was satisfactorily completed. On this system the steel electrode has a sheath of blue asbestos, which melts and flows down over the molten metal, thereby extinguishing the arc. This asbestos also forms a floating covering over the molten metal and protects it from oxidization. In order to give further protection, an aluminium wire is carried down by the side of the steel electrode, so that the molten aluminium may take up any oxygen which gets beneath the flux. Messrs. Laird built a small sea-going vessel, the S.S. " Fullagar," in 1920, using the Quasi-Arc process. If welding can be adopted as the general practice, a very large saving should arise in the cost of labour, and an appreciable saving in the case of weight and material.

FlG. 50.

Isherwood System. For many years warships have been built on the longitudinal system of framing, i.e. the principal structural members of the framing run fore and aft in continuous girders, the transverse framing being of a secondary character (apart from bulk- heads), and fitted between the longitudinal girders as necessary for local support. This system of framing has not found general accept- ance for merchant ships, because of the theory long held by ship- owners that a merchant ship must have such strong transverse frames that she may ground in an ordinary berth with a cargo on board and without damage. With the improved wharf accommoda- tion now available for important vessels this idea is being gradually relinquished. The most important movement in this connexion was inaugurated by Mr. (later Sir) Joseph Isherwood, who devised a plan for utilizing the whole of the framing of the bottom of the ship and of the decks so that it might be incorporated as part of the structural girder strength of the ship. In 1908, six ships were built of 31,000 tons; for the next six years, 40 or 50 ships were built per annum; but in 1915, under war conditions, the number very greatly increased, and in 1918, 250 ships of nearly 2,500,000 tons dead- weight capacity were built. Clearer holds, greater strength and a saving of about 10% of weight of structure are obtained, as well as decreased cost of building. By June 1921 1,400 ships, aggregating 12,000,000 dead-weight, had been built on this system.

The combination of a longitudinal system in the double bottom, and a transverse system above the bottom, has been adopted by Mr. W. Millar of Greenock, and several vessels have been built on the Millar system. Other systems in which a longitudinal construe-