In nautical parlance, the draft or draught of a sail is a degree of curvature in a horizontal cross-section. Any sail experiences a force from the prevailing wind just because it impedes the air's passage. A sail with draft also functions as an airfoil when set at an angle slightly greater than the angle of the wind, producing lift which then propels. A sail is any type of surface intended to generate thrust by being placed in a wind âin essence a vertically-oriented wing. ... Curvature is the amount by which a geometric object deviates from being flat. ... Wind is the roughly horizontal movement of air (as opposed to an air current) caused by uneven heating of the Earths surface. ... An airfoil (in American English, or aerofoil in British English) is the shape of a wing or blade (of a propeller or ships screw or sail) as seen in cross-section. ...
The word "belly" is also used in reference to the draft of a sail (i.e. "More belly in the main sail."). Look up Belly in Wiktionary, the free dictionary Belly can refer to: The abdomen, the part of the body between the pelvis and the thorax. ...