luff

Luff is a term used in sailing and vexillology to describe the edge of a sail or flag that is closest to the wind or to the hoist, respectively. In sailing, the luff is the forward, or leading, edge of a sail that runs from the tack at the lower corner to the head at the upper corner and is typically attached to the mast or controlled by halyards. This edge is often reinforced with a boltrope or luff rope to maintain shape and strength. The luff is one of three primary edges of a sail, the others being the leech (trailing edge) and the foot (bottom edge).

Luffing and trimming are key concepts in sailing. To luff a sail means to steer the bow toward the wind until the sail begins to flap or lose its full shape, reducing forward propulsion. Luffing can occur when sailing too close to the wind, when the sail is improperly trimmed, or when the wind shifts. Skilful sailors manage the luff with careful adjustment of halyards, sheets, and the sail’s angle to the wind to maintain power and speed without excessive flutter.

In vexillology, the luff refers to the edge of a flag nearest the hoist, the side attached to the flagpole. The luff may contain grommets or a sleeve for a halyard and is distinct from the fly edge, which is the outer, often longer, edge.

The term also appears as a surname in various contexts.