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Tacking or coming about is a sailing maneuver by which a sailing vessel (which is sailing approximately into the wind) turns its bow into the wind through the 'no-go zone' so that the direction from which the wind blows changes from one side to the other. For example, if a vessel is sailing on a starboard tack with the wind blowing from the right side and tacks, it will end up on a port tack with the wind blowing from the left side. See the image at the right; the red arrow indicates the wind direction. This maneuver is frequently used when the desired direction is (nearly) directly into the wind. In practice, the sails are set at an angle of 45° to the wind for conventional sailships and the tacking course is kept as short as possible before a new tack is set in. Rotor ships can tack much closer to the wind, 20 to 30°. The opposite maneuver, i.e. turning the stern through the wind, is called jibing (or ''wearing'' on square-rigged ships). Tacking more than 180° to avoid a jibe (mostly in harsh conditions) is sometimes referred to as a 'chicken jibe'. ==Technical usage== Tacking is sometimes confused with ''beating to windward'', which is a process of beating a course upwind and generally implies (but does not require) actually coming about. In the accompanying figure, the boat is seen to tack three times while beating to windward. When used without a modifier, the term "tacking" is always synonymous with "coming about"; however, some find it acceptable to say "tack downwind"; i.e., change tack by jibing rather than coming about. Racers often use this maneuver because most modern sailboats (especially larger boats with spinnakers and a variety of staysails) sail substantially faster on a broad reach than when running "dead" downwind. The extra speed gained by zigzagging downwind can more than make up for the extra distance that must be covered. Cruising boats also often tack downwind when the swells are also coming from dead astern (i.e., there is a "following sea"), because of the more stable motion of the hull. ''About'' is defined as: "To go about is to change the course of a ship by tacking. Ready about, or boutship, is the order to prepare for tacking."〔 at Internet Archive〕 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「Tacking (sailing)」の詳細全文を読む スポンサード リンク
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