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''Voima'' is a Finnish state-owned icebreaker. Built by Wärtsilä Hietalahti shipyard in Helsinki in 1954, she was the first icebreaker in the world to be equipped with two bow propellers〔Stephen J. Jones: (Ships In Ice - A Review ). Proceedings of the 25th Symposium on Naval Hydrodynamics.〕〔Stephen J. Jones: (A history of icebreaking ships ). Ocean Sovereignty, Vol. 3, No. 1, 2008.〕〔 and generated widespread publicity that helped the Finnish shipbuilding industry to become the world leader in icebreaker design. ''Voima'' was extensively refitted in 1978–1979. , she is the oldest and smallest icebreaker in service in Finland and is scheduled to be replaced by a new icebreaker by the winter of 2015–16. However, she might remain in limited service after this. == Development and construction == In the Moscow Armistice, signed on 19 September 1944, Finland agreed to pay war reparations of US$300 million to the Soviet Union. The war reparations, paid in the form of ships and machinery over six years, included the newest steam-powered state-owned icebreakers ''Voima'' and ''Jääkarhu''. This left Finland with one modern diesel-electric icebreaker, ''Sisu'', which had been damaged by a naval mine during the war, and four older steam-powered icebreakers. Of these, especially ''Murtaja'' and ''Apu'' were considered nearly obsolete and their efforts in the Archipelago Sea were sometimes described being "mostly of moral nature". As a result, only the ports of Hanko and Turku were kept open through the first post-war winters.〔Kaukiainen (1992), pp. 226–231.〕 In 1946, the Finnish Government appointed a committee to start planning the rebuilding of the Finnish icebreaker fleet. The committee, consisting of the director of the Finnish Maritime Administration, Svante Sundman, and two experienced Finnish shipbuilders, K. Albin Johansson and Ossian Tybeck, delivered its final report on the construction of a new icebreaker in the following year.〔 The main dimensions of the new 4,415-ton icebreaker, large enough to escort 10,000-ton dry cargo ships or 16,000-ton tankers, were based on the old ''Jääkarhu'', but the triple-expansion steam engines were replaced with a modern diesel-electric propulsion system, similar to the 1939-built ''Sisu'', with a combined output of 10,500 shp.〔 In the early drafts, the new icebreaker was designed with three propellers (two in the stern and one in the bow) and an asymmetric stem that would compensate for the transverse force caused by the bow propeller.〔Ramsay (1949), pp. 352–353.〕 However, these features were later dropped after extensive model testing and co-operation with Swedish naval architects in favor of a completely new design.〔Jäänmurtaja Voima ja sen neljä potkuria. Suomen Laivasto 2/1954, pp. 27–28.〕 The result was, in many respects, the most advanced icebreaker in the world at the time. Although bow propellers had been a common feature in icebreakers around the world for decades, it was incorrectly believed that they helped with the actual icebreaking process by reducing the pressure under the ice in front of the ship. However, extensive research and recent experiences had shown that bow propellers improved the icebreaking capability because their flushing effect reduced the friction between the broken ice floes and the hull of the ship. The drawback of a single bow propeller was that it would lubricate only one side of the hull. As a result, the new Finnish icebreaker was designed with two bow propellers which would produce a more powerful and, more importantly, symmetric flushing effect. Furthermore, a vessel with four propellers would be extremely maneuverable and capable of even moving sideways. Prior to the new Finnish icebreaker, only the 1947-built Canadian ferry ''Abegweit'' had been fitted with such propulsion arrangement. While the new ship was not the most powerful icebreaker in the world at the time, the power-to-displacement and power-to-beam ratios of the new Finnish icebreaker put her in a class of her own among icebreaking ships.〔 The construction of the first Finnish post-war icebreaker was awarded to Wärtsilä in 1948, but due to lack of funding the keel of the ship was not laid down at the Hietalahti shipyard until 29 May 1951.〔〔(Jäänmurtajat Suomessa ). 〕 The working name of the newbuilding was ''Into'',〔Den nya havsisbryaren - ett teknisk framsteg. Suomen Laivasto, 3/1950. Pages 63–65.〕 but when she was launched on 27 November 1952, the new Finnish icebreaker was christened ''Voima'' by Sylvi Kekkonen, wife of the Prime Minister and future President of Finland, Urho Kekkonen.〔Uusi jäänsärkijä laskettu vesille Hietalahden telakalla. Suomen Laivasto, 12/1952. Page 246.〕 Her name, Finnish for "strength", had previously been given to one of the icebreakers that had been handed over to the Soviet Union after the war. The official sea trials were completed on 12 February 1954 and on the following day ''Voima'' was handed over to the Finnish Maritime Administration.〔〔 The new state-owned icebreaker generated widespread publicity and the follow-up orders allowed Wärtsilä to establish the Finnish shipbuilding industry as the world leader in the design and construction of icebreaking ships.〔Turunen and Partanen (2011), p. 40.〕 After ''Voima'', the shipyard delivered three icebreakers of similar design to the Soviet Union (''Kapitan Belousov'', ''Kapitan Voronin'' and ''Kapitan Melehov'') and one for the Swedish Maritime Administration (''Oden'').〔〔Suurtunnustus jäänmurtajien rakentajillemme. Suomen Laivasto 12/1954, page 248.〕 By the late 1980s, Wärtsilä had produced about 60 percent of the worldwide icebreaker fleet,〔(Finland-Transport Equipment ). Mongabay.com. 〕 including all Finnish icebreakers in service at the time. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Voima (1952 icebreaker)」の詳細全文を読む スポンサード リンク
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