The proto- Austronesian words for sail, lay(r), and some other rigging parts date to about 3000 BCE when this group began their Pacific expansion. Crab claw rigs įijian voyaging outrigger boat with a crab claw sail Practical experience on the Duyfken replica confirmed the role of the lateen mizzen. The extensive amount of contemporary maritime art showing the lateen mizzen on 16th and 17th century ships often has the sail furled. It did not, however, provide much of the propulsive force of these vessels – rather serving as a balancing sail that was needed for some manoeuvres in some sea and wind conditions. Adittionally, lateen sails were used for the mizzen on early three-masted ships, playing a significant role in the development of the full-rigged ship. The popularity of the caravel in Northern European waters from about 1440 made lateen sails familiar in this part of the world. There is, however, good iconographic evidence of square sails being used by Arab, Persian and Indian ships in this region in, for instance, 1519. The lateen was adopted by Arab seafarers (usually in the sub-type: the settee sail), but the date is uncertain, with no firm evidence for their use in the Western Indian Ocean before 1500 CE. Lateen provided a cheaper rig to build and maintain, with no degradation of performance. Analysis of voyages described in contemporary accounts and also in various replica vessels demonstrates that the performance of square rig and lateen were very similar. It has been a common and erroneous presumption among maritime historians that lateen had significantly better sailing performance than the square rig of the same period. Both the increasing popularity of the lateen and the changes to the contemporary square rig are suggested to be cost saving measures, reducing the number of expensive components needed to fit out a ship. They did not become common until the 5th century, when there is evidence that the Mediterranean square sail (which had been in wide use throughout the classical period) was undergoing a simplification of its rigging components. Lateen sails emerged by around the 2nd century CE in the Mediterranean. Main articles: Lateen and Fore-and-aft rig Other non-rotating airfoils that power sailing craft include wingsails, which are rigid wing-like structures, and kites that power kite-rigged vessels, but do not employ a mast to support the airfoil and are beyond the scope of this article. Battens may be used to extend the trailing edge of a sail beyond the line of its attachment points. In use, they may be designed to be curved in both directions along their surface, often as a result of their curved edges. They are typically raised by a line, called a halyard, and their angle with respect to the wind is usually controlled by a line, called a sheet. Sails may be attached to a mast, boom or other spar or may be attached to a wire that is suspended by a mast. Sails are unable to generate propulsive force if they are aligned too closely to the wind. The more that the angle of attack diverges from the apparent wind as a sailing craft turns downwind, the more drag increases and lift decreases as propulsive forces, until a sail going downwind is predominated by drag forces. On points of sail where it is possible to align the leading edge of the sail with the apparent wind, the sail may act as an airfoil, generating propulsive force as air passes along its surface-just as an airplane wing generates lift-which predominates over aerodynamic drag retarding forward motion. Angle of attack is often constrained by the sailing craft's orientation to the wind or point of sail. Apparent wind is the air velocity experienced on the moving craft and is the combined effect of the true wind velocity with the velocity of the sailing craft. Sails may be made from a combination of woven materials-including canvas or polyester cloth, laminated membranes or bonded filaments-usually in a three- or four-sided shape.Ī sail provides propulsive force via a combination of lift and drag, depending on its angle of attack-its angle with respect to the apparent wind. Sailing hydrofoil catamaran with wingsail.Ī 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.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |