Draft (sail) on:
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In nautical parlance, the draft or draught of a
In nautical parlance, the draft or draught of a sail
A sail is a tensile structure, which is made from fabric or other membrane materials, that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may b ...
refers to the amount and shape of curvature
In mathematics, curvature is any of several strongly related concepts in geometry that intuitively measure the amount by which a curve deviates from being a straight line or by which a surface deviates from being a plane. If a curve or su ...
in a horizontal cross-section. Any sail experiences a force from the prevailing wind
Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...
just because it impedes the air's passage. A sail with draft also functions as an airfoil
An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more Lift (force), lift than Drag (physics), drag. Wings, sails and propeller blades are examples of airfoils. Foil (fl ...
when set at an angle slightly greater than the angle of the wind, producing lift which then propels the vessel.
The word " belly" is also used in reference to the draft of a sail (''i.e.'' "More belly in the main sail.").
See also
*Forces on sails
Forces on sails result from movement of air that interacts with sails and gives them motive power for sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and sail-powered land vehicles. Similar principles in a rotatin ...
*Sail components
Sail components include the features that define a sail's shape and function, plus its constituent parts from which it is manufactured. A sail may be classified in a variety of ways, including by its orientation to the vessel (e.g. ''fore-and-a ...
References
Nautical terminology {{water-sports-stub