A jibe (US) or gybe (Britain) is a sailing maneuver whereby a sailing vessel reaching downwind turns its stern through the wind, which then exerts its force from the opposite side of the vessel. Because the mainsail boom can swing across the cockpit quickly, jibes are potentially dangerous to person and rigging compared to tacking. Therefore, accidental jibes are to be avoided while the proper technique must be applied so as to control the maneuver. For square-rigged ships, this maneuver is called wearing ship.
In this maneuver, the mainsail will cross the center of the boat while the jib is pulled to the other side of the boat. If a spinnaker is up, its pole will have to be manually moved to the other side, to remain opposite the mainsail. In a dinghy, raising the centerboard can increase the risk of capsizing during what can be a somewhat violent maneuver, although the opposite is true of a dinghy with a flat, planing hull profile: raising the centerboard reduces heeling moment during the maneuver and so reduces the risk of capsize.
The other way to change the side of the boat that faces the wind is turning the bow of the boat into, and then through, the direction of the wind. This operation is known as tacking or coming about. Tacking more than 180° to avoid a jibe is sometimes referred to as a "chicken jibe".
Use
Many sailboats are significantly faster sailing on a broad reach than running (sailing straight downwind). Thus the increased speed of a zig-zag course of alternating broad reaches can more than make up for the extra distance it takes over a straight downwind course. Jibing is also common in racing, which often use a triangular course marked with buoys; the most direct way of rounding a buoy may be to jibe.
Jibing is a less common technique than tacking, since a sailboat can sail straight downwind, whereas it cannot sail directly into the wind and has to sail a zig-zag course at alternating angles into the wind. However, a jibe can generally be completed more quickly than a tack because the boat never turns into the wind, and thus a jibing boat's sails are always powered whereas a tacking boat's luffing sails are un-powered while the bow crosses through or into the direction of the wind.
'Wearing ship' is the alternative maneuver for a square rigged ship that wishes to avoid the difficulties and hazards of tacking. Light winds, heavy seas, worn-out gear, and poor vessel or crew performance are all reasons a ship may choose to wear instead of tack. Compared to boats with a fore-and-aft rig, a square rigger can jibe without any difficulty or risk of accident. However, since these craft cannot point close to the wind, they may find it difficult to maintain turning and forward momentum as the bow passes through the large no-go zone when tacking. If the ship loses steering way, it can be 'taken aback,' with the wind pressing on the forward surface of the sails and caught in irons. By driving the vessel backwards through the water, this puts excessive strain on the ship's masts, spars and rigging, could break the rudder, and in severe weather could dismast the ship. With tacking to windward carrying these risks, in some situations it was considered quicker and safer to travel upwind by executing a series of jibes, turning the vessel across the wind through 270 degrees rather than the 90 degrees of a tack. This, however, would result in considerable ground lost to leeward with each jibe. Wearing has been judged to be unseamanlike except in heavy weather.
When running (sailing nearly directly downwind) in a sloop, one may 'jibe' only the mainsail to the opposite side of the boat. This keeps both the main and jib exposed to the wind resulting in a more efficient use of wind. Setting the mainsail and the jib on opposite sides of the boat is often referred to as running "goose-winged", "gull-winged", or "wing-and-wing". When running wing-and-wing, a light spinnaker pole or whisker pole is often used to hold the clew of the foresail out to the windward side of the boat.