Luff

Language: jargon: sailing

n.
1. The leading edge of a sail. The windward edge.
2. The forward portion of the sail's pocket or camber.
3. The rounded portion of the bow quarters.
4. An oar or foil on the leeward bow to steer the bow nearer the wind.

v.
1. Increasing the sail's angle of attack to the wind to the point at which turbulence develops on the leeward side. (The laminar flow of air is disrupted as the pressure differential reaches zero and the sail oscillates.)
2. To point closer to the wind, especially to shoot into the no-go zone.
3. To shake the sail, to slat or flap, rather than fill with the wind.

The leading edge of the sail is called it's luff, except on square sails which have two leeches, the weather leech and the leeward or lee leech.

The belly or pocket of the sail is usually near the forward edge of the sail, and curve nearest the front is also known as the luff. As a boat sails too near the wind, the airflow over the sail gets turbulent the sail reduces or stops propelling the boat. The leading curve of the sail (the luff) will first lose its taughtness, then soften and start to ripple, which is the first signs of luffing. Pointing even nearer the wind will develop violent slatting and flapping, the leech may begin machine-gunning, and the sail will develop drag bringing the boat to a halt. (hove-to)

Sailors will add tell-tales to the sail near the luff and nearer the leech to give visual cues whether the sail is beginning to luff. Tell-tales should stream aft. If they droop downward, the sail is probably not trimmed close enough to the wind; if they stream upward or flutter wildly the sail is probably over-trimmed.

See also:
• leech
• luff tackle
• heave-to

References:
• http://dictionary.reference.com/
• Edwards, Fred; Sailing as a Second Language; International Marine Publishing Company; © 1988 Highmark Publishing Ltd.; ISBN 0-87742-965-0
• Marino, Emiliano; The Sailmaker's Apprentice: A guide for the self-reliant sailor; International Marine/Ragged Mountan Press; © 1994 International Marine; ISBN 0-07-157980-X

Luff (?), n. [OE. lof, prob. a sort of timber by which the course of a ship was directed, perh. a sort of paddle; cf. D. loef luff, loeven to luff. The word is perh. akin to E. glove. Cf. Aloof.] Naut. (a)

The side of a ship toward the wind

The act of sailing a ship close to the wind

The roundest part of a ship's bow

The forward or weather leech of a sail, especially of the jib, spanker, and other fore-and-aft sails.

Luff tackle, a purchase composed of a double and single block and fall, used for various purposes. Totten. -- Luff upon luff, a luff tackle attached to the fall of another luff tackle. R. H. Dana, Jr.

© Webster 1913.

Luff (?), v. i. [imp. & p. p. Luffed (?); p. pr. & vb. n. Luffing.] Naut.

To turn the head of a vessel toward the wind; to sail nearer the wind; to turn the tiller so as to make the vessel sail nearer the wind.

To luff round, ∨ To luff alee, to make the extreme of this movement, for the purpose of throwing the ship's head into the wind.

© Webster 1913.