Gybe

Also spelled jibe.

Of a sailing vessel: to change direction by turning away from (when sailing close to the wind) or across (when running before the wind) the wind. Large, heavy sailing vessels, such as older, square-rigged ships, could not easily tack when sailing close to the wind and would gybe almost all the time. Modern sailing boats, especially Bermuda-rigged, can easily tack and that is the faster and more efficient method of changing direction.

When running before the wind, gybing can produce a moment of instability. When changing direction, the sail loses power and weather helm ensues. This results in the helmsman increasing the rudder force. The sails then fill and the boat begins to roll to the same side as the sails and this sail force adds with the rudder force to generate even more rolling. This can continue to increase to the point of capsize if the vessel doesn't have a heavy keel (such as a kayak with a daggerboard or leeboard). Even with a heavy keel, gybing with a big jib or spinnaker can result in the sail taking on water and either holding the boat down or dismasting the vessel.

Gybing also describes the situation where a sailboat becomes unstable when running directly before the wind and a perturbation results in the boat rolling. The normal reaction of a little-experienced helmsman is to turn away from the roll, which only serves to increase the roll. One must turn into the roll to correct this situation.