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A sail is a
tensile structure A tensile structure is a construction of elements carrying only tension and no compression or bending. The term ''tensile'' should not be confused with tensegrity, which is a structural form with both tension and compression elements. Tensile st ...
—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including
sailing ship A sailing ship is a sea-going vessel that uses sails mounted on masts to harness the power of wind and propel the vessel. There is a variety of sail plans that propel sailing ships, employing square-rigged or fore-and-aft sails. Some ships c ...
s,
sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminology ...
s,
windsurfers Windsurfing is a wind propelled water sport that is a combination of sailing and surfing. It is also referred to as "sailboarding" and "boardsailing", and emerged in the late 1960s from the aerospace and surf culture of California. Windsurfing ga ...
, ice boats, and even sail-powered land vehicles. 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. A sail provides propulsive force via a combination of lift and drag, depending on its
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
—its angle with respect to the
apparent wind Apparent wind is the wind experienced by a moving object. Definition of apparent wind The ''apparent wind'' is the wind experienced by an observer in motion and is the relative velocity of the wind in relation to the observer. The ''velocity o ...
. 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. Angle of attack is often constrained by the sailing craft's orientation to the wind or
point of sail A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface. The principal points of sail roughly correspond to 45° segments of a circle, starting with 0° directly into the wind. ...
. 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 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 turbine. ...
, generating propulsive force as air passes along its surface—just as an airplane wing generates
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobile ...
—which predominates over
aerodynamic drag In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fl ...
retarding forward motion. 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. Sails are unable to generate propulsive force if they are aligned too closely to the wind. Sails may be attached to a mast, boom or other
spar SPAR, originally DESPAR, styled as DE SPAR, is a Dutch multinational that provides branding, supplies and support services for independently owned and operated food retail stores. It was founded in the Netherlands in 1932, by Adriaan van Well, ...
or may be attached to a wire that is suspended by a mast. They are typically raised by a line, called a ''
halyard In sailing, a halyard or halliard is a line (rope) that is used to hoist a ladder, sail, flag or yard. The term ''halyard'' comes from the phrase "to haul yards". Halyards, like most other parts of the running rigging, were classically made of n ...
'', and their angle with respect to the wind is usually controlled by a line, called a sheet. In use, they may be designed to be curved in both directions along their surface, often as a result of their curved edges.
Batten A batten is most commonly a strip of solid material, historically wood but can also be of plastic, metal, or fiberglass. Battens are variously used in construction, sailing, and other fields. In the lighting industry, battens refer to linea ...
s may be used to extend the trailing edge of a sail beyond the line of its attachment points. Other non-rotating airfoils that power sailing craft include
wingsail A wingsail, twin-skin sail or double skin sail is a variable-camber aerodynamic structure that is fitted to a marine vessel in place of conventional sails. Wingsails are analogous to airplane wings, except that they are designed to provide lif ...
s, which are rigid wing-like structures, and
kite A kite is a tethered heavier than air flight, heavier-than-air or lighter-than-air craft with wing surfaces that react against the air to create Lift (force), lift and Drag (physics), drag forces. A kite consists of wings, tethers and anchors. ...
s that power kite-rigged vessels, but do not employ a mast to support the airfoil and are beyond the scope of this article.


Rigs

Sailing craft employ two types of rig, the
square rig Square rig is a generic type of sail and rigging arrangement in which the primary driving sails are carried on horizontal spars which are perpendicular, or square, to the keel of the vessel and to the masts. These spars are called ''yards'' and ...
and the
fore-and-aft rig A fore-and-aft rig is a sailing vessel rigged mainly with sails set along the line of the keel, rather than perpendicular to it as on a square rigged vessel. Description Fore-and-aft rigged sails include staysails, Bermuda rigged sails, gaff ...
. The ''square rig'' carries the primary driving sails on horizontal
spars The United States Coast Guard (USCG) Women's Reserve, also known as the SPARS (SPARS was the acronym for "Semper Paratus—Always Ready"), was the women's branch of the United States Coast Guard Reserve. It was established by the United States ...
, which are perpendicular or
square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90-degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length adj ...
, to the
keel The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in Br ...
of the vessel and to the masts. These spars are called ''
yards The yard (symbol: yd) is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement standardized as exactly 0.914 ...
'' and their tips, beyond the last stay, are called the ''
yardarms A yard is a spar on a mast from which sails are set. It may be constructed of timber or steel or from more modern materials such as aluminium or carbon fibre. Although some types of fore and aft rigs have yards, the term is usually used to desc ...
''. A ship mainly so rigged is called a ''square-rigger''. The square rig is aerodynamically most efficient when ''
running Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions). This is ...
'' (sailing downwind). A ''fore-and-aft rig'' consists of sails that are set along the line of the
keel The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in Br ...
rather than perpendicular to it. Vessels so rigged are described as ''fore-and-aft rigged''.


History

Archaeological studies of the Cucuteni-Trypillian culture ceramics show use of sailing boats from the sixth millennium BCE onwards. Excavations of the
Ubaid period The Ubaid period (c. 6500–3700 BC) is a prehistoric period of Mesopotamia. The name derives from Tell al-'Ubaid where the earliest large excavation of Ubaid period material was conducted initially in 1919 by Henry Hall and later by Leonard Wool ...
(c. 6000–4300 BCE) in
Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...
provide direct evidence of sailing boats.


Square rigs

Sails from ancient Egypt are depicted around 3200 BCE,The sea-craft of prehistory, p76, by Paul Johnstone, Routledge, 1980 where
reed boats Reed boats and rafts, along with dugout canoes and other rafts, are among the oldest known types of boats. Often used as traditional fishing boats, they are still used in a few places around the world, though they have generally been replaced with ...
sailed upstream against the River
Nile The Nile, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered ...
's current. Ancient
Sumer Sumer () is the earliest known civilization in the historical region of southern Mesopotamia (south-central Iraq), emerging during the Chalcolithic and early Bronze Ages between the sixth and fifth millennium BC. It is one of the cradles of c ...
ians used square rigged sailing boats at about the same time, and it is believed they established sea trading routes as far away as the
Indus valley The Indus ( ) is a transboundary river of Asia and a trans-Himalayan river of South and Central Asia. The river rises in mountain springs northeast of Mount Kailash in Western Tibet, flows northwest through the disputed region of Kashmir, ...
.
Greeks The Greeks or Hellenes (; el, Έλληνες, ''Éllines'' ) are an ethnic group and nation indigenous to the Eastern Mediterranean and the Black Sea regions, namely Greece, Cyprus, Albania, Italy, Turkey, Egypt, and, to a lesser extent, oth ...
and
Phoenicians Phoenicia () was an ancient Semitic-speaking peoples, ancient thalassocracy, thalassocratic civilization originating in the Levant region of the eastern Mediterranean, primarily located in modern Lebanon. The territory of the Phoenician city-st ...
began trading by ship by around 1200 BCE. V-shaped square rigs with two spars that come together at the hull were the ancestral sailing rig of the
Austronesian peoples The Austronesian peoples, sometimes referred to as Austronesian-speaking peoples, are a large group of peoples in Taiwan, Maritime Southeast Asia, Micronesia, coastal New Guinea, Island Melanesia, Polynesia, and Madagascar that speak Austro ...
before they developed the fore-and-aft crab claw,
tanja Tanja ( sr, Тања) is a feminine given name. It may refer to: Mononyms *''Tanja'' (born 1983), Russian-Estonian singer, also known as Tanja Mihhailova Given name *Tanja Andrejeva (born 1978), Macedonian handball player * Tanja Bogosavljevi ...
and junk rigs. The date of introduction of these later Austronesian sails is disputed.


Lateen rigs

Lateen A lateen (from French ''latine'', meaning "Latin") or latin-rig is a triangular sail set on a long yard mounted at an angle on the mast, and running in a fore-and-aft direction. The settee can be considered to be an associated type of the same o ...
sails emerged by around the 2nd century CE in the Mediterranean. 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. 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. 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. 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. Lateen provided a cheaper rig to build and maintain, with no degradation of performance. 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. 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 popularity of the
caravel The caravel (Portuguese: , ) is a small maneuverable sailing ship used in the 15th century by the Portuguese to explore along the West African coast and into the Atlantic Ocean. The lateen sails gave it speed and the capacity for sailing win ...
in Northern European waters from about 1440 made lateen sails familiar in this part of the world. 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 A full-rigged ship or fully rigged ship is a sailing vessel's sail plan with three or more masts, all of them square-rigged. A full-rigged ship is said to have a ship rig or be ship-rigged. Such vessels also have each mast stepped in three se ...
. 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. The extensive amount of contemporary maritime art showing the lateen mizzen on 16th and 17th century ships often has the sail furled. Practical experience on the ''
Duyfken ''Duyfken'' (; Little Dove), also in the form ''Duifje'' or spelled ''Duifken'' or ''Duijfken'', was a small ship built in the Dutch Republic. She was a fast, lightly armed ship probably intended for shallow water, small valuable cargoes, bri ...
'' replica confirmed the role of the lateen mizzen.


Crab claw rigs

Austronesian invention of
catamaran A Formula 16 beachable catamaran Powered catamaran passenger ferry at Salem, Massachusetts, United States A catamaran () (informally, a "cat") is a multi-hulled watercraft featuring two parallel hulls of equal size. It is a geometry-stab ...
s,
outriggers An outrigger is a projecting structure on a boat, with specific meaning depending on types of vessel. Outriggers may also refer to legs on a wheeled vehicle that are folded out when it needs stabilization, for example on a crane that lifts ...
, and the bi-sparred triangular
crab claw sail The crab claw sail is a fore-and-aft triangular sail with spars along upper and lower edges. The crab claw sail was first developed by the Austronesian peoples some time around 1500 BC. It is used in many traditional Austronesian cultures in Isl ...
s enabled their ships to sail for vast distances in open ocean. It led to the
Austronesian Expansion The Austronesian peoples, sometimes referred to as Austronesian-speaking peoples, are a large group of peoples in Taiwan, Maritime Southeast Asia, Micronesia, coastal New Guinea, Island Melanesia, Polynesia, and Madagascar that speak Austron ...
. From Taiwan, they rapidly settled the islands of
Maritime Southeast Asia Maritime Southeast Asia comprises the countries of Brunei, Indonesia, Malaysia, the Philippines, Singapore, and East Timor. Maritime Southeast Asia is sometimes also referred to as Island Southeast Asia, Insular Southeast Asia or Oceanic Sout ...
, then later sailed further onwards to
Micronesia Micronesia (, ) is a subregion of Oceania, consisting of about 2,000 small islands in the western Pacific Ocean. It has a close shared cultural history with three other island regions: the Philippines to the west, Polynesia to the east, and ...
,
Island Melanesia Island Melanesia is a subregion of Melanesia in Oceania. It is located east of New Guinea island, from the Bismarck Archipelago to New Caledonia.Steadman, 2006. ''Extinction & biogeography of tropical Pacific birds'' See also Archaeology a ...
,
Polynesia Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...
, and
Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
, eventually settling a territory spanning half the globe. 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. The absence of proto-Austronesian words for some rigging parts is evidence that the more complex sails were later developments, so calling into question the traditionalist model of Austronesian sail development. Austronesian rigs were distinctive in that they had spars supporting both the upper and lower edges of the sails (and sometimes in between), in contrast to western rigs which only had a spar on the upper edge. The sails were also made from salt-resistant woven leaves, usually from pandan plants. Crab claw sails used with
single-outrigger Outrigger boats are various watercraft featuring one or more lateral support floats known as outriggers, which are fastened to one or both sides of the main hull. They can range from small dugout canoes to large plank-built vessels. Outrigger ...
ships in
Micronesia Micronesia (, ) is a subregion of Oceania, consisting of about 2,000 small islands in the western Pacific Ocean. It has a close shared cultural history with three other island regions: the Philippines to the west, Polynesia to the east, and ...
,
Island Melanesia Island Melanesia is a subregion of Melanesia in Oceania. It is located east of New Guinea island, from the Bismarck Archipelago to New Caledonia.Steadman, 2006. ''Extinction & biogeography of tropical Pacific birds'' See also Archaeology a ...
,
Polynesia Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...
, and
Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
were intrinsically unstable when tacking leeward. To deal with this, Austronesians in these regions developed the shunting technique in sailing, in conjunction with uniquely reversible single-outriggers. In the rest of
Austronesia The Austronesian peoples, sometimes referred to as Austronesian-speaking peoples, are a large group of peoples in Taiwan, Maritime Southeast Asia, Micronesia, coastal New Guinea, Island Melanesia, Polynesia, and Madagascar that speak Austrone ...
, crab claw sails were mainly for
double-outrigger A trimaran (or double-outrigger) is a multihull boat that comprises a main hull and two smaller outrigger hulls (or "floats") which are attached to the main hull with lateral beams. Most modern trimarans are sailing yachts designed for recreati ...
(
trimaran A trimaran (or double-outrigger) is a multihull boat that comprises a main hull and two smaller outrigger hulls (or "floats") which are attached to the main hull with lateral beams. Most modern trimarans are sailing yachts designed for recreati ...
s) and double-hulled (
catamaran A Formula 16 beachable catamaran Powered catamaran passenger ferry at Salem, Massachusetts, United States A catamaran () (informally, a "cat") is a multi-hulled watercraft featuring two parallel hulls of equal size. It is a geometry-stab ...
s) boats, which remained stable even leeward. In western
Island Southeast Asia Maritime Southeast Asia comprises the countries of Brunei, Indonesia, Malaysia, the Philippines, Singapore, and East Timor. Maritime Southeast Asia is sometimes also referred to as Island Southeast Asia, Insular Southeast Asia or Oceanic Sout ...
, later square sails also evolved from the crab claw sail, the
tanja Tanja ( sr, Тања) is a feminine given name. It may refer to: Mononyms *''Tanja'' (born 1983), Russian-Estonian singer, also known as Tanja Mihhailova Given name *Tanja Andrejeva (born 1978), Macedonian handball player * Tanja Bogosavljevi ...
and the junk rig, both of which retained the Austronesian characteristic of having more than one spar supporting the sail.


Aerodynamic forces

Aerodynamic forces on sails depend on wind speed and direction and the speed and direction of the craft. The direction that the craft is traveling with respect to the ''true wind'' (the wind direction and speed over the surface) is called the "point of sail". The speed of the craft at a given point of sail contributes to the apparent wind (VA)—the wind speed and direction as measured on the moving craft. The apparent wind on the sail creates a total aerodynamic force, which may be resolved into ''drag''—the force component in the direction of the apparent wind—and ''lift''—the force component
normal Normal(s) or The Normal(s) may refer to: Film and television * ''Normal'' (2003 film), starring Jessica Lange and Tom Wilkinson * ''Normal'' (2007 film), starring Carrie-Anne Moss, Kevin Zegers, Callum Keith Rennie, and Andrew Airlie * ''Norma ...
(90°) to the apparent wind. Depending on the alignment of the sail with the apparent wind, lift or drag may be the predominant propulsive component. Total aerodynamic force also resolves into a forward, propulsive, driving force—resisted by the medium through or over which the craft is passing (e.g. through water, air, or over ice, sand)—and a lateral force, resisted by the underwater foils, ice runners, or wheels of the sailing craft. For apparent wind angles aligned with the entry point of the sail, the sail acts 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 turbine. ...
and lift is the predominant component of propulsion. For apparent wind angles behind the sail, lift diminishes and drag increases as the predominant component of propulsion. For a given true wind velocity over the surface, a sail can propel a craft to a higher speed, on points of sail when the entry point of the sail is aligned with the apparent wind, than it can with the entry point not aligned, because of a combination of the diminished force from airflow around the sail and the diminished apparent wind from the velocity of the craft. Because of limitations on speed through the water, displacement sailboats generally derive power from sails generating lift on points of sail that include close-hauled through broad reach (approximately 40° to 135° off the wind). Because of low friction over the surface and high speeds over the ice that create high apparent wind speeds for most points of sail, iceboats can derive power from lift further off the wind than displacement boats. File:Sailboat on broad reach with spinnaker.jpg, Spinnaker set for a broad reach, mobilizing both lift and drag. File:Spinnaker trimmed for broad reach.jpg, Spinnaker cross-section trimmed for a broad reach showing air flow. File:Amante Choate 48 photo D Ramey Logan.jpg, Spinnaker downwind, primarily mobilizing drag. File:Symmetrical spinnaker with following apparent wind.jpg, Spinnaker cross-section with following apparent wind, showing air flow.


Types

Each rig is configured in a ''
sail plan A sail plan is a description of the specific ways that a sailing craft is rigged. Also, the term "sail plan" is a graphic depiction of the arrangement of the sails for a given sailing craft.> In the English language, ships were usually describe ...
'', appropriate to the size of the sailing craft. A sail plan is a set of drawings, usually prepared by a
naval architect This is the top category for all articles related to architecture and its practitioners. {{Commons category, Architecture occupations Design occupations Architecture, Occupations ...
which shows the various combinations of sail proposed for a
sailing ship A sailing ship is a sea-going vessel that uses sails mounted on masts to harness the power of wind and propel the vessel. There is a variety of sail plans that propel sailing ships, employing square-rigged or fore-and-aft sails. Some ships c ...
. Sail plans may vary for different wind conditions—light to heavy. Both square-rigged and fore-and-aft rigged vessels have been built with a wide range of configurations for single and multiple masts. Types of sail that can be part of a sail plan can be broadly classed by how they are ''attached'' to the sailing craft: *''To a stay'' – Sails attached to stays, include
jib A jib is a triangular sail that sets ahead of the foremast of a sailing vessel. Its tack is fixed to the bowsprit, to the bows, or to the deck between the bowsprit and the foremost mast. Jibs and spinnakers are the two main types of headsail ...
s, which are attached to
forestay On a sailing vessel, a forestay, sometimes just called a stay, is a piece of standing rigging which keeps a mast from falling backwards. It is attached either at the very top of the mast, or in fractional rigs between about 1/8 and 1/4 from the t ...
s and
staysail A staysail ("stays'l") is a fore-and-aft rigged sail whose Sail components#Edges, luff can be affixed to a stays (nautical), stay running forward (and most often but not always downwards) from a mast (sailing), mast to the deck (ship), deck, the b ...
s, which are mounted on other stays (typically wire cable) that support other masts from the bow aft. *''To a mast'' – Fore-and-aft sails directly attached to the mast at the luff include
gaff-rigged Gaff rig is a sailing rig (configuration of sails, mast and stays) in which the sail is four-cornered, fore-and-aft rigged, controlled at its peak and, usually, its entire head by a spar (pole) called the ''gaff''. Because of the size and shap ...
quadrilateral and
Bermuda ) , anthem = "God Save the King" , song_type = National song , song = " Hail to Bermuda" , image_map = , map_caption = , image_map2 = , mapsize2 = , map_caption2 = , subdivision_type = Sovereign state , subdivision_name = , e ...
triangular sails. *''To a spar'' – Sails attached to a spar include both
square sail Square rig is a generic type of sail and rigging arrangement in which the primary driving sails are carried on horizontal spars which are perpendicular, or square, to the keel of the vessel and to the masts. These spars are called ''yards'' and ...
s and such fore-and-aft quadrilateral sails as
lug rig The lug sail, or lugsail, is a fore-and-aft, four-cornered sail that is suspended from a spar, called a yard. When raised, the sail area overlaps the mast. For "standing lug" rigs, the sail may remain on the same side of the mast on both the port ...
s, junk and
spritsail The spritsail is a four-sided, fore-and-aft sail that is supported at its highest points by the mast and a diagonally running spar known as the sprit. The foot of the sail can be stretched by a boom or held loose-footed just by its sheets. A spr ...
s and such triangular sails as the
lateen A lateen (from French ''latine'', meaning "Latin") or latin-rig is a triangular sail set on a long yard mounted at an angle on the mast, and running in a fore-and-aft direction. The settee can be considered to be an associated type of the same o ...
, and the crab claw. *''To a halyard'' –
Spinnaker A spinnaker is a sail designed specifically for sailing off the wind on courses between a reach (wind at 90° to the course) to downwind (course in the same direction as the wind). Spinnakers are constructed of lightweight fabric, usually n ...
s are the predominant sail supported solely by a halyard. High-performance yachts, including the International C-Class Catamaran, have used or use rigid ''wing sails'', which perform better than traditional soft sails but are more difficult to manage. A rigid wing sail was used by '' Stars and Stripes'', the defender which won the 1988 America's Cup, and by ''
USA-17 ''USA-17'' (formerly known as ''BMW Oracle Racing 90'' or ''BOR90'') is a sloop rigged racing trimaran built by the American sailing team BMW Oracle Racing to challenge for the 2010 America's Cup. Designed by VPLP Yacht Design with consulta ...
'', the challenger which won the 2010 America's Cup. ''USA 17s performance during the 2010 America's Cup races demonstrated a
velocity made good Velocity made good, or VMG, is a term used in sailing, especially in yacht racing, indicating the speed of a sailboat towards (or from) the direction of the wind. The concept is useful because a sailboat cannot sail directly upwind, and thus often ...
upwind of over twice the wind speed and downwind of over 2.5 times the wind speed and the ability to sail as close as 20 degrees off the apparent wind.


Shape

The shape of a sail is defined by its edges and corners in the plane of the sail, laid out on a flat surface. The edges may be curved, either to extend the sail's shape as an airfoil or to define its shape in use. In use, the sail becomes a curved shape, adding the dimension of depth or ''draft''. *''Edges'' – The top of all sails is called the ''head'', the leading edge is called the ''luff'' on fore-and-aft sails and on windward leech symmetrical sails, the trailing edge is the ''leech'', and the bottom edge is the ''foot''. The ''head'' is attached at the throat and peak to a gaff,
yard The yard (symbol: yd) is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement standardized as exactly 0.914 ...
, or sprit. For a triangular sail the ''head'' refers to the topmost corner. :A fore-and-aft triangular mainsail achieves a better approximation of a wing form by extending the leech aft, beyond the line between the head and clew on an arc called the ''roach'', rather than having a triangular shape. This added area would flutter in the wind and not contribute to the efficient airfoil shape of the sail without the presence of
battens A batten is most commonly a strip of solid material, historically wood but can also be of plastic, metal, or fiberglass. Battens are variously used in construction, sailing, and other fields. In the lighting industry, battens refer to linea ...
. Offshore cruising mainsails sometimes have a ''hollow leech'' (the inverse of a roach) to obviate the need for battens and their ensuing likelihood of chafing the sail. The roach on a square sail design is the arc of a circle above a straight line from clew to clew at the foot of a square sail, which allows the foot of the sail to clear stays coming up the mast, as the sails are rotated from side to side. *''Corners'' – The names of corners of sails vary, depending on shape and symmetry. In a triangular sail, the corner where the luff and the leech connect is called the ''head''. On a square sail, the top corners are ''head cringles'', where there are grommets, called
cringle A cringle is an eye through which to pass a rope. In nautical settings, the word refers to a small hole anywhere along the edge or in the corner of a sail, rimmed with stranded cordage and worked into the boltrope. Typically it encloses a meta ...
s. On a quadrilateral sail, the ''peak'' is the upper aft corner of the sail, at the top end of a gaff or other spar. The ''throat'' is the upper forward corner of the sail, at the bottom end of a gaff or other spar. Gaff-rigged sails, and certain similar rigs, employ two
halyard In sailing, a halyard or halliard is a line (rope) that is used to hoist a ladder, sail, flag or yard. The term ''halyard'' comes from the phrase "to haul yards". Halyards, like most other parts of the running rigging, were classically made of n ...
s to raise the sails: the
throat halyard In sailing, the throat halyard (or throat for short) is a line that raises the end of a gaff nearer to the mast, as opposed to the peak halyard which raises the end further from the mast. Such rigging was normal in classic gaff-rigged schooner ...
raises the forward, throat end of the gaff, while the
peak halyard In sailing, the peak halyard (or peak for short) is a line that raises the end of a gaff which is further from the mast, as opposed to the throat halyard which raises the end which is nearer to the mast. Such rigging was normal in classic gaff-rigg ...
raises the aft, peak end. :The corner where the leech and foot connect is called the ''clew'' on a fore-and-aft sail. On a jib, the sheet is connected to the clew; on a mainsail, the sheet is connected to the boom (if present) near the clew. ''Clews'' are the lower two corners of a square sail. Square sails have sheets attached to their clews like triangular sails, but the sheets are used to pull the sail down to the yard below rather than to adjust the angle it makes with the wind. The corner where the leech and the foot connect is called the ''clew''. The corner on a fore-and-aft sail where the luff and foot connect is called the ''tack'' and, on a mainsail, is located where the boom and mast connect. :In the case of a symmetrical
spinnaker A spinnaker is a sail designed specifically for sailing off the wind on courses between a reach (wind at 90° to the course) to downwind (course in the same direction as the wind). Spinnakers are constructed of lightweight fabric, usually n ...
, each of the lower corners of the sail is a clew. However, under sail on a given tack, the corner to which the spinnaker sheet is attached is called the ''clew'', and the corner attached to the spinnaker pole is referred to as the ''tack''. On a square sail underway, the tack is the windward clew and also the line holding down that corner. *''Draft'' – Those triangular sails that are attached to both a mast along the luff and a boom along the foot have depth, called ''
draft Draft, The Draft, or Draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a vessel ...
'', which results from the luff and foot being curved, rather than straight as they are attached to those spars. Draft creates a more efficient
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 turbine. ...
shape for the sail. Draft can also be induced in triangular
staysails A staysail ("stays'l") is a fore-and-aft rigged sail whose Sail components#Edges, luff can be affixed to a stays (nautical), stay running forward (and most often but not always downwards) from a mast (sailing), mast to the deck (ship), deck, the b ...
by adjustment of the sheets and the angle from which they reach the sails.


Material

Sail characteristics derive, in part, from the design, construction and the attributes of the fibers, which are woven together to make the sail cloth. There are several key factors in evaluating a fiber for suitability in weaving a sail-cloth: '' initial modulus'', '' breaking strength (tenacity)'', '' creep'', and '' flex strength''. Both the initial cost and its durability of the material define its cost-effectiveness over time. Traditionally, sails were made from
flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. Textiles made from flax are known in ...
or
cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus ''Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor perce ...
canvas Canvas is an extremely durable plain-woven fabric used for making sails, tents, marquees, backpacks, shelters, as a support for oil painting and for other items for which sturdiness is required, as well as in such fashion objects as handbags ...
. Materials used in sails, as of the 21st century, include
nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from petro ...
for spinnakers—where light weight and elastic resistance to shock load are valued—and a range of fibers, used for triangular sails, that includes
Dacron Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...
,
aramid Aramid fibers, short for aromatic polyamide, are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic-rated body armor fabric and ballistic composites, in marine cordage, ma ...
fibers—including
Kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...
, and other
liquid crystal polymer Liquid crystal polymers (LCPs) are polymers with the property of liquid crystal, usually containing aromatic rings as mesogens. Despite uncrosslinked LCPs, polymeric materials like liquid crystal Elastomer, elastomers (LCEs) and liquid crystal n ...
fibers—including
Vectran Vectran is a manufactured fiber, spun from a liquid-crystal polymer (LCP) created by Celanese Corporation and now manufactured by Kuraray. Chemically it is an aromatic polyester produced by the polycondensation of 4-hydroxybenzoic acid and 6-hyd ...
. Woven materials, like Dacron, may specified as either high or low ''tenacity'', as indicated, in part by their denier count (a unit of measure for the
linear mass density Linear density is the measure of a quantity of any characteristic value per unit of length. Linear mass density (titer in textile engineering, the amount of mass per unit length) and linear charge density (the amount of electric charge per unit ...
of fibers).


Construction

''Cross-cut'' sails have the panels sewn parallel to one another, often parallel to the foot of the sail, and are the least expensive of the two sail constructions. Triangular cross-cut sail panels are designed to meet the mast and stay at an angle from either the warp or the weft (on the
bias Bias is a disproportionate weight ''in favor of'' or ''against'' an idea or thing, usually in a way that is closed-minded, prejudicial, or unfair. Biases can be innate or learned. People may develop biases for or against an individual, a group, ...
) to allow stretching along the luff, but minimize stretching on the luff and foot, where the fibers are aligned with the edges of the sail. ''Radial'' sails have panels that "radiate" from corners in order to efficiently transmit stress and are typically higher-performance than cross-cut sails. A ''bi-radial'' sail has panels radiating from two of three corners; a ''tri-radial'' sail has panels radiating from all three corners. Mainsails are more likely to be bi-radial, since there is very little stress at the tack, whereas head sails (spinnakers and jibs) are more likely to be tri-radial, because they are tensioned at their corners. Higher-performance sails may be laminated, constructed directly from multiple plies of filaments,
fiber Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
s,
taffeta Taffeta (archaically spelled taffety or taffata) is a crisp, smooth, plain woven fabric made from silk, cuprammonium rayons, acetate, and polyester. The word is Persian (تافته) in origin and means "twisted woven". As clothing, it is used in ...
s, and
films A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmosphere ...
—instead of woven textiles—and adhered together. ''Molded sails'' are laminated sails formed over a curved mold and adhered together into a shape that does not lie flat. Conventional sail panels are sewn together. Sails are tensile structures, so the role of a seam is to transmit a tensile load from panel to panel. For a sewn textile sail this is done through thread and is limited by the strength of the thread and the strength of the hole in the textile through which it passes. Sail seams are often overlapped between panels and sewn with zig-zag stitches that create many connections per unit of seam length. Whereas textiles are typically sewn together, other sail materials may be ultrasonically welded—a technique whereby high-frequency
ultrasonic Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies fr ...
acoustic
vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic function, periodic, such as the motion of a pendulum ...
s are locally applied to workpieces being held together under pressure to create a solid-state weld. It is commonly used for
plastics Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...
, and especially for joining dissimilar
materials Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geologic ...
. Sails feature reinforcements of fabric layers where lines attach at
grommet Curtain grommets, used among others in shower curtains. A grommet is a ring or edge strip inserted into a hole through thin material, typically a sheet of textile fabric, sheet metal or composite of carbon fiber, wood or honeycomb. Grommets ar ...
s or
cringle A cringle is an eye through which to pass a rope. In nautical settings, the word refers to a small hole anywhere along the edge or in the corner of a sail, rimmed with stranded cordage and worked into the boltrope. Typically it encloses a meta ...
s. A bolt rope may be sewn onto the edges of a sail to reinforce it, or to fix the sail into a groove in the boom, in the mast, or in the luff foil of a roller-furling jib. They may have stiffening features, called
battens A batten is most commonly a strip of solid material, historically wood but can also be of plastic, metal, or fiberglass. Battens are variously used in construction, sailing, and other fields. In the lighting industry, battens refer to linea ...
, that help shape the sail, when full length, or just the roach, when present. They may have a variety of means of
reefing Reefing reduces the area of a sail, usually by folding or rolling one edge of the canvas in on itself and attaching the unused portion to a spar or a stay, as the primary measure to preserve a sailing vessel's stability in strong winds. Restoring ...
them (reducing sail area), including rows of short lines affixed to the sail to wrap up unused sail, as on square and gaff rigs, or simply grommets through which a line or a hook may pass, as on Bermuda mainsails. Fore-and-aft sails may have tell-tales—pieces of yarn, thread or tape that are affixed to sails—to help visualize airflow over their surfaces. Zagiel horyzont.svg, Cross-cut Zagiel birad.svg, Bi-radial Zagiel gwiazda.svg, Tri-radial


Running rigging

The lines that attach to and control sails are part of the
running rigging Running rigging is the rigging of a sailing vessel that is used for raising, lowering, shaping and controlling the sails on a sailing vessel—as opposed to the standing rigging, which supports the mast and bowsprit. Running rigging varies bet ...
and differ between square and fore-and-aft rigs. Some rigs shift from one side of the mast to the other, e.g. the dipping lug sail and the lateen. The lines can be categorized as those that support the sail, those that shape it, and those that control its angle to the wind.


Fore-and-aft rigged vessels

Fore-and-aft rigged vessels have rigging that supports, shapes, and adjusts the sails to optimize their performance in the wind, which include the following lines: *''Supporting'' – ''Halyards'' raise sails and control luff tension. ''Topping lifts'' hold booms and yards aloft. On a gaff sail, ''
brail Brails, in a sailing ship, are small lines used to haul in or up the edges (leeches) or corners of sails, before furling.''Webster's Revised Unabridged Dictionary'', 1913. On a ship rig, these brails are most often found on the mizzen sail. T ...
s'' run from the leech to the spar to facilitate furling. *''Shaping'' – ''Barber haulers'' adjust a spinnaker/jib sheeting angle inboard at right angles to the sheet with a ring or clip on the sheet attached to cordage which is secured and adjusted via fairlead and cam cleat. '' Kicking straps/boom vangs'' control a boom-footed sail's leech tension by exerting downward force mid-boom. ''
Cunningham Cunningham is a surname of Scottish origin, see Clan Cunningham. Notable people sharing this surname A–C *Aaron Cunningham (born 1986), American baseball player *Abe Cunningham, American drummer * Adrian Cunningham (born 1960), Australian ...
s'' tighten the luff of a boom-footed sail by pulling downward on a cringle in the luff of a mainsail above the tack. ''
Downhaul The downhaul is a line which is part of the rigging on a sailboat; it applies downward force on a spar or sail. The most common downhaul on a modern sailboat is attached to the spinnaker pole, though this may be referred to as the foreguy in some ...
s'' lower a sail or a yard and can adjust the tension on the luff of a sail. ''
Outhaul An outhaul is a control line found on a sailboat. It is an element of the running rigging, used to attach the mainsail Parts of a sail#Corners, clew to the boom (sailing), boom and tensions the Sail components#Edges, foot of the sail. It commonly ...
s'' control the foot tension of a boom-footed sail. *''Adjusting angle to the wind'' – '' Sheets'' control angle of attack with respect to the apparent wind, the amount of leech "twist" near the head of the sail, and the foot tension of loose-footed sails. A ''
preventer A gybe preventer, preventer, or jibe-guard, is a mechanical device on a sailing vessel which limits the boom's ability to swing unexpectedly across the boat due to an unplanned accidental jibe. During an unplanned accidental jibe (or ''gybe'') ...
'' attaches to the end of the boom from a point near the mast to prevent an accidental gybe. '' Guys'' control spinnaker pole angle with respect to the apparent wind.


Square-rigged vessels

Square-rigged vessels require more controlling lines than fore-and-aft rigged ones, including the following. *''Supporting'' – ''Halyards'' raise and lower the yards. ''Brails'' run from the leech to the spar to facilitate furling. '' Buntlines'' serve to raise the foot up for shortening sail or for furling. ''Lifts'' adjust the tilt of a yard, to raise or lower the ends off the horizontal. ''Leechlines'' run to the
leech Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...
(outer vertical edges) of a sail and serve to pull the leech both in and up when furling. *''Shaping'' – ''Bowlines'' run from the leech forward towards the bow to control the weather leech, keeping it taut and thus preventing it from curling back on itself. '' Clewlines'' raise the clews to the yard above. *''Adjusting angle to the wind'' – '' Braces'' adjust the fore and aft angle of a
yard The yard (symbol: yd) is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement standardized as exactly 0.914 ...
(i.e. to rotate the yard laterally, fore and aft, around the mast). ''Sheets'' attach to the clew to control the sail's angle to the wind. ''
Tack TACK is a group of archaea acronym for Thaumarchaeota (now Nitrososphaerota), Aigarchaeota, Crenarchaeota (now Thermoproteota), and Korarchaeota, the first groups discovered. They are found in different environments ranging from acidophilic the ...
s'' haul the clew of a square sail forward.


Gallery

File:Bladerider-8.jpg, International Moth on foils. File:Funboard.jpg,
Windsurfer Windsurfing is a wind propelled water sport that is a combination of sailing and surfing. It is also referred to as "sailboarding" and "boardsailing", and emerged in the late 1960s from the aerospace and surf culture of California. Windsurfing ga ...
. File:Bladef16-1up.jpg,
Formula 16 The Formula 16 (F16) sport catamaran is an ISAF recognised 5 m long beach catamaran with an asymmetric spinnaker setup. It is actively sailed in two modes: doublehanded with a jib (''2-up''), and singlehanded without a jib (''1-up''). Its c ...
catamaran A Formula 16 beachable catamaran Powered catamaran passenger ferry at Salem, Massachusetts, United States A catamaran () (informally, a "cat") is a multi-hulled watercraft featuring two parallel hulls of equal size. It is a geometry-stab ...
. File:DN ice boat--Ice Nine--Lake Sunapee NH.jpg, DN class ice boat. File:LandYacht.jpg, Land sailing craft.


See also

;Components *
Marine canvas Marine canvas refers to a varied array of fabrics used in the fabrication and production of awnings, covers, tarps, sunshades, signs and banners for the advertising, boating, trucking, tenting, structural and medical industries. The term "marine ca ...
* Sail Class Markings *
Baggywrinkle Baggywrinkle is a soft covering for cables (or any other obstructions) to reduce sail chafe. There are many points in the rig of a large sailing ship where the sails come into contact with the standing rigging; unprotected sails would soon devel ...
;Concepts *
Sail twist Sail twist is a phenomenon in sailing where the head of the sail is at a different angle of incidence from the foot of the sail in order to change the lift distribution with height. Twist is measured by comparing the angle of a straight line betwe ...
;Related *
Cruising (maritime) Cruising by boat is an activity that involves living for extended time on a vessel while traveling from place to place for pleasure. Cruising generally refers to trips of a few days or more, and can extend to round-the-world voyages. History ...
*
SkySails SkySails Group GmbH is a Hamburg-based company that sells kite rigs to propel cargo ships, large yachts and fishing vessels by wind energy as well as airborne wind energy systems for electricity production from high-altitude winds. Busines ...
;Types of sails *
Mainsail A mainsail is a sail rigged on the main mast of a sailing vessel. * On a square rigged vessel, it is the lowest and largest sail on the main mast. * On a fore-and-aft rigged vessel, it is the sail rigged aft of the main mast. The sail's foot ...
*
Mizzen The mast of a sailing vessel is a tall spar, or arrangement of spars, erected more or less vertically on the centre-line of a ship or boat. Its purposes include carrying sails, spars, and derricks, and giving necessary height to a navigation ligh ...
*
Wingsail A wingsail, twin-skin sail or double skin sail is a variable-camber aerodynamic structure that is fitted to a marine vessel in place of conventional sails. Wingsails are analogous to airplane wings, except that they are designed to provide lif ...


Legend


Notes


References


Further reading

* * * * * * * * *


External links


Sailboats database: sailing yacht specifications worldwideSail Design Software


* {{Authority control Ancient Egyptian technology Chinese inventions Cucuteni–Trypillia culture Marine propulsion Sailboat components Sailing rigs and rigging