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 ma ...

is a degree of

curvature In mathematics, curvature is any of several strongly related concepts in geometry. Intuitively, the curvature is the amount by which a curve deviates from being a straight line, or a surface deviates from being a plane. For curves, the can ...

in a horizontal cross-section. Any sail experiences a force from the prevailing

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...

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 the cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbin ...

when set at an angle slightly greater than the angle of the wind, producing lift which then propels. The word "

belly Belly may refer to: Anatomy * The abdomen, the part of the body between the pelvis and the thorax; or the stomach ** A beer belly, an overhang of fat above the waist, presumed to be caused by regular beer drinking ** Belly dance * The fleshy, cent ...

" is also used in reference to the draft of a sail (''i.e.'' "More belly in the main sail.").

References

Nautical terminology {{water-sports-stub

See also

References