Luffing

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You can help expand this article with text translated from the corresponding article in French. (October 2024) Click [show] for important translation instructions. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Consider adding a topic to this template: there are already 1,618 articles in the main category, and specifying|topic= will aid in categorization. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing French Wikipedia article at [[:fr:Lof]]; see its history for attribution. You may also add the template {{Translated|fr|Lof}} to the talk page. For more guidance, see Wikipedia:Translation.

In sailing, 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.^[1]

A sailboat can also be "luffed" slightly without completely de-powering the sails. Often this occurs on the point of sail 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"), 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. To offset luffing at the top of the sail one should move the sail "lead" forward until the point where the "telltales" break evenly.

Luffing is also a process of power kites when they stall and the front (or leading) edge falls downwards.