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A sister ship is a ship of the same class as, or of virtually identical design to, another ship. Such vessels share a near-identical hull and superstructure layout, similar displacement, and roughly comparable features and equipment. Often, sisters become more differentiated during their service as their equipment (in the case of military ships, their armament) are separately altered. For instance, the U.S. warships , , , and , are all sister ships, each being an . The most famous sister ships were the White Star Line's , and . As with some other liners, these sisters worked as running mates.〔(Olyympic Class ) Encyclopedia Titanica〕 Other sister ships include the Royal Caribbean International's and . ''Half-sister'' refers to a ship of the same class, but with some significant differences. One example of half-sisters are the First World War-era British s where the first two ships had four guns, but the last ship, , had two guns instead. Another example are the American s of the Second World War that came in "long-hull" and "short-hull" versions. The generally accepted commercial distinction of a ''sister ship'' are Type: Identical main type (Bulk, Tank, RoRo, etc.) * DWT: +/- 10% on the DWT (So if the ship is 100,000 DWT, then 90,000 to 110,000 DWT) * Built: +/- 5 years (So if the ship is built in 2000, then built 1995-2005) * Builder: Identical shipbuilding company name (NOT the ship yard location or the Country of build) The critical overriding criteria are the same hull design. For example the popular TESS-57 standard design built by Tsunishi Shipbuilding are built in Japan, China and the Philippines. All the ships of this design are classed as ''sister ships''. The International Maritime Organization defined ''sister ship'' in IMO resolution MSC/Circ.1158 in 2006. Criteria included: * A sister ship is a ship built by the same yard from the same plans * The acceptable deviation of lightship displacement should be between 1 and 2% of the lightship displacement of the lead ship, depending on the length of the ship. == See also == * Ship naming and launching 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「sister ship」の詳細全文を読む スポンサード リンク
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