A spinnaker is a sail designed for sailing off the wind from a reaching course to a downwind, i.e. with the wind 90–180° off bow. The spinnaker fills with wind and balloons out in front of the boat when it is deployed, called flying, it is constructed of lightweight fabric nylon, is brightly coloured. It may be optimised for a particular range of wind angles, as either a reaching or a running spinnaker, by the shaping of the panels and seams; the spinnaker is called a kite, or a chute because it somewhat resembles a parachute in both construction and appearance. This should not be confused with the spinnaker chute, a hull fitting sometimes used for launching and recovering the spinnaker. A purported etymology has the first boat to carry this sail being a Cowes yacht named Sphinx, from which "Sphinx's Acre" and "Spinnaker". A spinnaker is used for sailing with the direction of the wind. Symmetrical spinnakers have large amounts of camber. Both lift and drag propel the boat forward. Reaching spinnakers have less camber.
A well designed spinnaker will have taut leading edges. Such a sail will have a smooth curve when filled, with no bubbles or depressions caused by inconsistent stretching of the fabric. Any deviations from a smooth curve will cause the airflow over the leeward side of the sail to separate causing a reduction in lift and reduced performance. There are two main categories of spinnakers and asymmetric depending on whether a plane of symmetry exists for that particular sail. Asymmetric spinnakers operate more like a jib, generating lift from the side, rather than the top like a symmetric spinnaker; this makes asymmetrics a better choice on reaching courses than symmetric spinnakers, which excel when running. While a equipped racing boat might have a number of spinnakers, both symmetric and asymmetric, to cover all courses and wind conditions, cruising boats always use an asymmetric, due to the broader application and easier handling afforded by the asymmetric; the symmetric one is the most classic type, running symmetrical alongside the boat controlled by lines known as a sheet and a guy running from the lower two corners of the sail.
The windward line, or guy, is attached to the corner called the tack of the sail, is stabilized by a spinnaker pole. The leeward line is called the sheet, it is used to control the shape of the sail. The spinnaker pole must be moved in each gybe, is quite difficult for beginners to use. However, it can be sailed in all downwind wind directions. Symmetric spinnakers when sailing across the wind develop most of their lift on the forward quarter, where the airflow remains attached; when set for reaching, the leading edges of a symmetric spinnaker should be nearly parallel to the wind, so the flow of air over the leading edge remains attached. When reaching, the sail camber allows only some attached flow over the leeward side of the spinnaker. On running the spinnaker is angled for maximum drag, with the spinnaker pole at right angles to the apparent wind; the symmetric spinnaker requires care when packing, since the three corners must be available on the top of the packing. Asymmetrical spinnaker resembling large jibs and flown from spinnaker poles are not a new idea and date back to at least the 19th Century.
However in the 1980s a new concept appeared. Since the 1960s many faster sailing craft, starting with catamaran classes, had discovered that it is faster to sail downwind on a series of broad reaches with efficient airflow across the sail rather than directly downwind with the sails stalled; this technique had developed to the extent that in bar conversation at the end of one season Andrew Buckland observed that the 18s had sailed all season without pulling the spinnaker pole back from the forestay and that all the systems could be simplified by eliminating the pole and setting the spinnaker from a fixed bowsprit. The concept evolved to a sail with a loose luff much more like a conventional spinnaker than the old jib style asymmetric sails. Julian Bethwaite was the first to rig and sail a boat with one the next season, followed shortly by Andrew Buckland; the first modern offshore sailboats to incorporate a retractable bow sprit and an asymmetric spinnaker was the J/Boats J/105. The concept has spread through the sailing world.
The tack of the sail may be attached at the bow like a genoa but is mounted on a bowsprit a retracting one. If the spinnaker is mounted to a special bowsprit, it is possible to fly the spinnaker and the jib at the same time; the asymmetric has two sheets much like a jib, but is not attached to the forestay along the length of the luff, but only at the corners. Unlike a symmetric spinnaker, the asymmetric does not require a spinnaker pole, since it is fixed to the bow or bowsprit; the asymmetric is easy to gybe since it only requires releasing one sheet and pulling in the other one, passing the sail in front of the forestay. Asymmetrics are less suited to sailing directly downwind than spinnakers, so instead the boat will sail a zig-zag course downwind, gybing at the corners. An asymmetric spinnaker is effective on fast planing dinghies as their speed generates an apparent wind on the bow allowing them to sail more directly downwind, it is particu
The Optimist known as the ‘opti’ or'bathtub', is a small, single-handed sailing dinghy intended for use by children up to the age of 15. Contemporary boats are made of fibreglass, although wooden boats are still built, it is one of the most popular sailing dinghies in the world, with over 150,000 boats registered with the class and many more built but never registered. The dinghy is good for children learning to sail; the Optimist is recognized as an International Class by the International Sailing Federation. The Optimist was designed in 1947 by American Clark Mills at the request of the Clearwater Florida Optimist service club following a proposal by Major Clifford McKay to offer low-cost sailing for young people; the Optimist Club wanted more than a single-day event. Thus they were looking for a low-cost equivalent for sailing, he designed a simple pram that could be built from two 4' x 8' sheets of plywood, donated the plan to the Optimists. The design was modified and introduced to Europe by Axel Damgaard, spread outwards across Europe from Scandinavia.
The design was standardized in 1960 and became a strict One-Design in 1995. The Optimist is sailed in over 120 countries and it is one of only two yachts approved by the International Sailing Federation for sailors under 16; the single sail of the Optimist is sprit-rigged. Two battens stiffen the leech, it is secured evenly with ties along the luff to the mast and along the foot to the boom, pulled down by a vang/kicker. The light, slim third spar, the sprit, extends through a loop at the peak of the sail. Raising and lowering the sprit and adjusting the boom vang allow for adaptation of sail trim to a range of wind conditions; the Optimist has a small string outhaul on the end of the boom. It is correct to tighten the boomvang and sprit in heavy winds and loosen them in light winds; as well as this, huge adjustments can be made to sail shape, due to all of the ties running along the mast and boom. The spars are invariably aluminium in modern boats. A monograph-style "IO" insignia on the sail is a registered trade-mark and may only be used under licence from the International Optimist Association.
Optimists have a national sail number using the Olympic abbreviation of their country and a sequential numbers. E.g. RSA for South Africa; the Optimist has a pram hull formed from five pieces of plywood. It was the biggest hull. Just in front of a bulkhead, which partitions the boat nearly in half, is the daggerboard case. Right behind it on the centerline of the hull floor are attached a ratchet block; these anchor its pulley on the boom directly above. At the bow resides a thwart to support the mast which passes through a hole in its centre to the mast step mounted on the centre line of the boat; the painter, a rope used for securing a boat like a mooring line, is tied around the mast step. Buoyancy bags are installed inboard along each side in the front half of the boat and at the stern to add buoyancy in the event of capsizing. Two straps, known as "hiking straps", run lengthwise along the floor from bulkhead to stern; these and a tiller extension allow a sailor to hang off the side for weight distribution—commonly called "hiking out".
This can be crucial to maintaining the boat in near horizontal disposition during heavy air, allowing greater speed through the water and more manoeuvrability. The vast majority of hulls today are made of Fiberglass, although it is still possible to make and buy wooden hulls; the rudder and daggerboard may be made from plywood or a composite of foam, glass fibre, epoxy. While younger lighter sailors begin in Optimists, competitive sailors weigh between 35 and 55 kg. Optimists can be sailed by children from age 8 to 15; this wide range of weights, not typical of most dinghies is made possible by different cuts of sail. Due to its inherent stability, unstayed rig, robust construction and small sail, the Optimist can be sailed in winds of up to 30 knots. Optimists are manufactured to the same specification by over 20 builders on four continents. There is strong evidence. Sails and spars of differing qualities enable sailors to upgrade their equipment; the Optimist is the slowest dinghy in the world according to the RYA Portsmouth Yardstick scheme, with a Portsmouth number of 1646.
Its equivalent rating in the US scheme is a D-PN of 123.6. Optimists are used for beginners. Light weight sailors continue to race them up 14 to 15 years of age; the age limit is 15. Small children are sometimes "doubled up" but the boats are single-handers. Many sailing schools and yacht clubs own a number of them and they are the first boat most beginners will sail; the Optimist is the biggest youth racing class in the world. As well as the annual world championship the class has six continental championships, attended by a total of over 850 sailors a year. Many of the top world Optimist sailors have become world-class Laser Radial or 4.7 sailors after they "age-out" but many excel in double-handers such as the 420 and 29er. At the 2016 Olympics at least 85% of the boat skippers were former Optimist sailors; the first World Championships were held in Great Britain in 1962, they have since been arranged annually. For the first 20 years, the class was dominated by sailors from the Scandinavian countries, with 13 world champio
A sail is a tensile structure—made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, windsurfers, ice boats, 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—its angle with respect to the apparent wind. 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 constrained by the sailing craft's orientation to the wind or point of sail. 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.
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 to the wind. Sails may be attached to a mast, boom or other spar or may be attached to a wire, suspended by a mast, they are raised by a line, called a halyard, their angle with respect to the wind is controlled by a line, called a sheet. In use, they may be designed to be curved in both directions along their surface as a result of their curved edges. Battens 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 wingsails, which are rigid wing-like structures, kites that power kite-rigged vessels, but do not employ a mast to support the airfoil and are beyond the scope of this article. Sailing craft employ two types of the square rig and the fore-and-aft rig.
The square rig carries 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 their tips, beyond the last stay, are called the yardarms. A ship so rigged is called a square-rigger; the square rig is aerodynamically most efficient. A fore-and-aft rig consists of sails that are set along the line of the keel rather than perpendicular to it. Vessels so rigged. Archaeological studies of the Cucuteni-Trypillian culture ceramics show use of sailing boats from the sixth millennium BCE onwards. Excavations of the Ubaid period in Mesopotamia provides direct evidence of sailing boats. Sails from ancient Egypt are depicted around 3200 BCE, where reed boats sailed upstream against the River Nile's current. Ancient Sumerians used square rigged sailing boats at about the same time, it is believed they established sea trading routes as far away as the Indus valley; the proto-Austronesian words for sail and other rigging parts date to about 3000 BCE when this group began their Pacific expansion.
Greeks and Phoenicians began trading by ship by around 1200 BCE. Triangular fore-and-aft rigs were invented in the Mediterranean as single-yarded lateen sails and independently in the Pacific as the more efficient bi-sparred crab claw sail, continue to be used throughout the world. During the 16th-19th centuries other fore-and-aft sails were developed in Europe, such as the spritsail, gaff rig, genoa and Bermuda rig mainsail, improving the upwind sailing ability of European vessels; the fore-and-aft rig began as a convention of southern Europe and the Mediterranean Sea: the gentle climate made its use practical, in Italy a few centuries before the Renaissance it began to replace the square rig which had dominated all of Europe since the dawn of sea travel. Northern Europeans were resistant to adopting the fore-and-aft rig, despite having seen its use in the course of trade and during the Crusades; the Renaissance changed this: beginning in 1475, their use increased and within a hundred years the fore-and-aft rig was in common use on rivers and in estuaries in Britain, northern France, the Low Countries, though the square rig remained standard for the harsher conditions of the open North Sea as well as for trans-Atlantic sailing.
The lateen sail proved to have better upwind performance for smaller vessels. 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 is called the "point of sail". The speed of the craft at a given point of sail contributes to the apparent wind —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 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 resolves into a forward, driving force—resisted by the medium through or over which the craft is passing —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 and lift is the predominant component of propulsion.
In sailing, a course is the lowermost sail on a mast. This term is used predominantly in the plural to describe the lowest sails on a square rigged vessel, i.e. a ship's courses would be the foresail, and, on the rare occasions in which one is shipped, mizzen. Gaff-rigged vessels may use the term, but are more to refer to a mainsail, etc. A Bermuda- or lateen-rigged yacht, whether sloop, ketch or yawl, would not be described as having a course
Sailcloth encompasses a wide variety of materials that span those from natural fibers, such as flax, hemp or cotton in various forms of sail canvas, to synthetic fibers, including nylon, polyester and carbon fibers in a variety of woven and molded textiles. Doek is Dutch for cloth, evolved into the English word "duck" in reference to sail canvas. Duck was made from cotton or linen, with some use of hemp; these natural fibers have poor resistance to UV light and water absorption. Linen is stronger. Linen was the traditional fiber of sails. At first cotton was used as a matter of necessity in the United States as it was indigenous and the supply of flax was periodically interrupted by wars such as the War of 1812, during which demand for sailcloth for military use was high; as sail size grew linen was too heavy to be practical so cotton became more popular. Cotton did not replace linen worldwide until the end of the age of sail, it was not until the late 20th century that natural fibers were replaced by synthetics in mainstream use.
Cotton sailcloth is still used for sportswear and draperies. The traditional width for carded cotton sailcloth in the US was 23 inches while the British standard was 24 inches; the wa proa of the Caroline Islands traditionally used pandanus matting as sailcloth. The characteristics of a sail are due to design and the attributes of the fibers, which are woven together to make the sail cloth; the following sections discuss the attributes of fibers assuming a good design and careful construction. According to Mahr, there are six key factors in evaluating a fiber for suitability in weaving a sail-cloth: Initial modulus – The ability to resist stretching. Higher resistance is better for upwind sails. Breaking strength – Measured as a force per cross sectional area of fiber. Higher is better for sails. Creep – Describes the long term stretch of a fiber or fabric. A material with creep lose its shape over time. Resistance to ultraviolet light – Strength loss from exposure to the Sun’s UV rays measured by a standardized exposure test.
Flex strength – Strength lost due to bending, folding, or flogging, measured with an industry standard 50 fold test. Cost-effectiveness –Both the initial cost and its durability of the material define its cost-effectiveness over time. There is no perfect solution since in most cases the increase of one attribute results in the decreased attractiveness of another. Reduced stretch also reduces the flexibility causing a trade-off of performance for durability. Solving both problems sends the price out of range for most sailors. Nylon is used in spinnakers because of its light weight, high tensile strength, superior abrasion resistance and flexibility. However, it has a low modulus allowing too much stretch to be suitable for upwind sails. Nylon is more susceptible to UV and chemical degradation than polyesters and its physical properties can change due to moisture absorption. Polyethylene terephthalate, the most common type of polyester, is the most common fiber used in sailcloth. PET has excellent resiliency, high abrasion resistance, high UV resistance, high flex strength and low cost.
Low absorbency allows the fiber to dry quickly. PET has been replaced by stronger fibers for most serious racing applications, but remains the most popular sail cloth due to lower price and high durability. Dacron is the brand name of Dupont’s Type 52 high modulus fiber made for sailcloth. Allied Signal has produced. Other trade names include Terylene, Tetoron and Diolen. PEN known by Honeywell's trade name "Pentex", is another kind of polyester fiber, which stretches only 40% as much as standard PET fibers, but about twice as much as Kevlar 29; because it only shrinks about a third as much as a good PET, PEN can not be woven as tightly. PEN is better suited for making laminated sailcloth, where the fibers are laid straight for strength and are bonded to sheets of film for stability, or as a taffeta outer layer of a laminate, protecting a PET film. PEN laminates are an economical alternative for higher performance sail. Kevlar, an aramid fiber, has become the predominant fiber for racing sails, since it was introduced by DuPont in 1971.
It is stronger, has a higher strength to weight ratio than steel, has a modulus, five times greater than PET, about twice as high as PEN. There are two popular types of Kevlar: Type 29 and Type 49, the latter having a 50% higher initial modulus than Type 29 but a lower flex loss. DuPont has developed higher modulus Types 129, 149 and 159, but these have seen little use in sails, since as the modulus increases the flex strength decreases. DuPont has introduced Kevlar Edge, a fiber developed for sails with 25% higher flex strength and a higher modulus than Kevlar 49. Kevlar, along with other aramid fibers, have poor UV resistance and rapid loss of strength with flexing and flogging. Minimal flogging and careful handling can extend the life of a Kevlar sail. Technora is an aramid, produced in Japan by Teijin, has a lower modulus strength than Kevlar 29 but a s
A gennaker is a sail, developed around 1990. Used when sailing downwind, it is a cross between a spinnaker, it is not symmetric like a true spinnaker but is asymmetric like a genoa, but the gennaker is not attached to the forestay like a jib or genoa. The gennaker is rigged like a spinnaker but the tack is fastened to the hull or to a bowsprit, it has greater camber than a genoa. This is optimal for generating lift at larger angles of attack. An early form of gennaker was the "gollywhomper", used in the 1870s; the gennaker is a specialty sail used on racing boats to bridge the performance gap between a genoa and a spinnaker. It is sometimes the only downwind sail on board because it is easier to use and less expensive than a spinnaker. Due to its geometry, the sail is less prone to collapsing than a spinnaker. A gennaker is optimal for a beam reach, while an asymmetrical spinnaker is optimal for a broad reach or run
A wingsail is a variable-camber aerodynamic structure, fitted to a marine vessel in place of conventional sails. Wingsails are analogous to airplane wings, except that they are designed to provide lift on either side to accommodate being on either tack. Whereas wings adjust camber with flaps, wingsails adjust camber with a flexible or jointed structure. Wingsails are mounted on an unstayed spar—often made of carbon fiber for lightness and strength; the geometry of wingsails provides more lift, a better lift-to-drag ratio, than traditional sails. Wingsails are more expensive than conventional sails. Wingsails are of two basic constructions that create an airfoil, "soft" and "hard". L. Francis Herreshoff pioneered a precursor rig that had jib and main, each with a two-ply sail with leading edges attached to a rotating spar; the C Class Catamaran class has been experimenting and refining wingsails in a racing context since the 60s. Englishman, John Walker, explored the use of wingsails in cargo ships and developed the first practical application for sailing yachts in the 1990s.
Wingsails have been applied to small vessels, like the Optimist dinghy and Laser, to cruising yachts, most notably to high-performance multihull racing sailboats, like USA-17. The smallest craft have a unitary wing, manually stepped. Cruising rigs have a soft rig. High-performance rigs are assembled of rigid components and must be stepped and unstepped by shore-side equipment. Wingsails change camber, depending on tack, wind speed. A wingsail becomes more efficient with greater curvature towards on the downwind side. Since the windward side changes with each tack, so must sail curvature change; this happens passively on a conventional sail. On a wingsail, a change in camber requires a mechanism. Wingsails change camber to adjust for windspeed. On an aircraft flaps increase the camber or curvature of the wing, raising the maximum lift coefficient—the lift a wing can generate—at a lower speeds of air passing over it. A wingsail has the same need for camber adjustment, as windspeed changes—a straighter camber curvature as windspeed increases, more curved as it decreases.
Mechanisms for camber adjustment are similar for hard wingsails. Each employs independent leading and trailing airfoil segments that are adjusted independently for camber. More sophisticated rigs allow for variable adjustment of camber with height above the water to account for increased windspeed; the presence of rigging, supporting the mast of a conventional fore-and-aft rig limits sail geometry to shapes that are less efficient than the narrow chord of the wingsail. However, conventional sails are simple to adjust for windspeed by reefing. Wingsails are a fixed surface area. Conventional sails can be furled easily. Nielsen summarised the efficiencies of wingsails, compared with conventional sails, for different points of sail, as follows: Close-hauled: At 30° apparent wind, the wingsail has a 10-degree angle of attack and more lift, compared to the conventional sail plan and its angles of attack of 15° for the jib and 20° for the mainsail. Beam reach: At 90° apparent wind, the wingsail, positioned across the boat, functions efficiently as a wing, providing forward lift, whereas the jib of the conventional sail plan suffers from being difficult to shape as a wing.
Broad reach: At 135° apparent wind, the wingsail may be eased in such a manner that it still functions efficiently as a wing, whereas the jib and main sail no longer provide lift—instead they present themselves perpendicular to the wind and provide force from drag only