For the forward edge of a sail, see parts of a sail

Parts of a sail

In sailing the parts of a sail have common terminology for each corner and edge of the sail.-The corners:In a triangular sail, the upper point is known as the head; the halyard, the line which raises the sail, is attached to the head...

. For other uses, see luff

Luff

Luff or luffing may refer to:* Luffing, when a sailing sheet is eased so far past trim that airflow over the surface is disrupted* The leading edge of a sail...

.

In sailing

Sailing

Sailing is the propulsion of a vehicle and the control of its movement with large foils called sails. By changing the rigging, rudder, and sometimes the keel or centre board, a sailor manages the force of the wind on the sails in order to move the boat relative to its surrounding medium and...

, luffing refers to when a sailing vessel is steered far enough toward the direction of the wind ("windward"), or the sheet controlling a sail is eased so far past optimal trim, that airflow over the surfaces of the sail is disrupted and the sail begins to "flap" or "luff" (the luff of the sail is usually where this first becomes evident). This is not always done in error; for example, the sails will luff when the bow of the boat passes through the direction of the wind as the sailboat is tacked

Tack (sailing)

Tack is a term used in sailing that has different meanings in different contexts, variously a part of a sail, and an alignment with the wind. When using the latter sense, the maneuver of turning between starboard and port tack is either tacking or jibing....

.

A sailboat can also be "luffed" slightly without completely de-powering the sails. Often this occurs on the point of sail

Points of sail

Points of sail describes a sailing boat's course in relation to the wind direction.There is a distinction between the port tack and the starboard tack. If the wind is coming from anywhere on the port side, the boat is on port tack. Likewise if the wind is coming from the starboard side, the boat...

 known as close hauled, this is sometimes referred to as pinching or "feathering" and is sometimes done deliberately in order to make a more direct course toward an upwind destination (See: Beating to windward...

Tack (sailing)

Tack is a term used in sailing that has different meanings in different contexts, variously a part of a sail, and an alignment with the wind. When using the latter sense, the maneuver of turning between starboard and port tack is either tacking or jibing....

), or to "de-power" a sail on a windy day to maintain control of the sailboat. "Luffing" can also be used to slow or stop a sailboat in a controlled manner.

Luffing is also a process of power kite

Power kite

A power kite or traction kite is a large kite designed to provide significant pull to the user.They come in three main forms: foils, leading edge inflatables and supported leading edge. There are also rigid-framed kites and soft single skin kites. There are several different control systems used...

s when they stall and the front (or leading) edge falls downwards.