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	= Engineering Abstracts from 1946 =		= Engineering Abstracts from 1946 =

			== German Wartime Technical Developments. ==
			SCHADE, H. A., Commodore, U.S.N. Society of Naval Architects and Marine Engineers (New York), paper read at Annual Meeting, 14th November, 1946.

			A general description is given of certain selected items in Germany which have been reported by the U.S. Naval Technical Mission in Europe. The author's remarks fall under the following headings :-

			Submarines. The Type VllC submarine, of conventional design, was built in large numbers during the war. Of the revolutionary Type XXI, 119 were completed, but none went out on war service. This type was designed as a highly-manoeuvrable high-speed vessel, which could remain submerged for long periods and operate at greater depths than most submarines. The sukmerged speed was 18 knots, and the surface speed 16 knots with super-chargers and somewhat less without them ; back pressure in the Schnorchel (breathing-tube) prevented the engines from attaining their rated capacity, so the superchargers were removed as the Schnorchel was indispensable. Trouble with the hydraulic system, which was far more extensive than is usual in submarines, was a major defect of Type XXI. These vessels, about 250 ft. long and with all-welded hulls, were prefabricated in nine sections which were welded together.

			Surface Vessels. The all-welded triple-screw battleships Bismarck and Tirpitz were 821 ft. long, had load displacements of 52,700 tons, and were propelled at 30 knots by three sets of geared-turbine machinery totalling 150,000 s.h.p. A design known as battleship "H" was developed, and construction was started, but plans were changed frequently. Originally 910 ft. long, 56,400 tons displacement, and 30 knots on three shafts, each having four Diesels of 12,500 s.h.p. per engine, the ultimate design was 1,132 ft. long, 141,500 tons displacement, and 30 knots on four shafts, two with four Diesels each totalling 60,000 s.h.p. per shaft, and two shafts each with geared turbines of 80,000 s.h.p. per shaft. The Prinz Eugen, 692 ft. long with a load displacement of 19,500 tons and a speed of 32.5 knots, was fitted with anti-rolling tanks, and was propelled by three geared-turbine sets. The S-38, a Diesel-propelled wooden-hulled 45-knot torpedo boat, had special side rudders for decreasing the required power at high speeds.

			Turbines and Gears. In general, the German turbine propulsion equipment was inferior to similar American machinery. The policy of using single reduction gearing with three or four pinions meshing with the main gear resulted in low turbine speeds and high specific weights. Turbine design and manufacture were mediocre, and there was poor utilisation of energy in the heat cycle ; the steam conditions should have produced high propulsion efficiencies. Some specific plants are discussed.

			Diesel Engines. The six-cylinder and twenty-four cylinder M.A.N. were well-developed and reliable. The Daimler-Benz Model MB 511 is an outstanding four-cycle supercharged lightweight Diesel for naval craft ; on a continuous rating of 1,980 b.h.p. at 1,480 r.p.m., the bare engine weight is 4.4 lb/lb.h.p.

			The Hamburg Model Basin. A large variable-pressure cavitation water tunnel and a smaller tunnel were constructed, but were completed too late to be used. A new towing carriage, an extended towing basin, and a new manoeuvring basin were under construction.

			An appendix lists the relevant Naval Technical Mission Reports.

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