fok

Fok is a nautical term used in Dutch-speaking contexts to denote the foresail, the triangular headsail set forward of the mainsail on a fore-and-aft rig. It is one of the primary sails on many sailing vessels and plays a key role in determining balance and upwind performance.

In typical setups, the fok is attached to the forestay and is trimmed independently of the mainsail. It can be hoisted, reefed, or furled as wind conditions change. The size and type of fok influence how aggressively a boat points into the wind and how easily it can be steered on different courses. On larger or more modern rigs, the fok may be complemented or replaced by larger headsails such as a genoa when conditions favor more sail area.

Variants and terminology around the fok vary by vessel and region. While the fok generally refers to the foresail, sailors may use different names for specific headsails on a given boat, including overlapped or non-overlapped sails. The English equivalent is the jib, and related terms in other languages include German Fock as a similar concept.

Historical and contemporary context: the fok has long been a standard feature on Dutch and other northern European vessels and remains common on modern sailboats, from small cruisers to racing yachts. Proper handling involves coordinating the fok with the mainsail during tacks and jibes and adjusting its angle of attack to match wind and point of sail.

See also: jib, genoa, fore sail.