Tacking (sailing)

Tacking or coming about is a sailing maneuver by which a sailing vessel whose desired course is into the wind, not possible to do on a sailing vessel, turns its bow into the wind so that the direction from which the wind blows changes from one side to the other, allowing progress in the desired direction. The opposite maneuver to tacking is called jibing, or wearing on square-rigged ships, that is, turning the stern through the wind. No sailing vessel can move directly upwind, though that may be the desired direction, making this an essential maneuver of a sailing ship. A series of tacking moves, in a zig-zag fashion, is called beating, and allows sailing in the desired direction.

This maneuver is used for different effects in races, where one ship is not only sailing in a desired direction, but also concerned with slowing the progress of competitors.

Sailing ships cannot proceed directly into the wind, but often need to proceed in that direction. Movement is achieved by tacking. 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'.

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.

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Wikipedia