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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 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 (for hard wingsails). Wingsails are typically mounted on an unstayed spar—often made of carbon fiber for lightness and strength. The geometry of wingsails provides more lift, and a better lift-to-drag ratio, than traditional sails. Wingsails are more complex and expensive than conventional sails. Introduction Wingsails are of two basic constructions that create an airfoil, "soft" and "hard", both mounted on an unstayed rotating mast. Whereas hard wingsails are rigid structures that are stowed only upon removal from the boat, soft wingsails can be furled or stowed on board. L. Fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 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 often 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio. The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at sufficient lift. Lifting structures used in water include various foils, such as hydrofoils. Hydrodynamics is the governing science, rather than aerodynamics. Applications of underwater foils occur in hydroplanes, sailboats and submarines. Etymology and usage For many centuries, the word "wing", from the Old Norse ''vængr'', referred mainly to the foremost limbs of birds (in addition to the architectural aisle). But in recent centuries the word's meanin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Downwind
Windward () and leeward () are terms used to describe the direction of the wind. Windward is ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming; leeward is ''downwind'' from the point of reference, i.e. along the direction towards which the wind is going. The side of a ship that is towards the leeward is its "lee side". If the vessel is heeling under the pressure of crosswind, the lee side will be the "lower side". During the Age of Sail, the term ''weather'' was used as a synonym for ''windward'' in some contexts, as in the ''weather gage''. Because it captures rain, the windward side of a mountain tends to be wet compared to the leeward it blocks. Origin The term "lee" comes from the middle-low German word // meaning "where the sea is not exposed to the wind" or "mild". The terms Luv and Lee (engl. Windward and Leeward) have been in use since the 17th century. Usage Windward and leeward directions (and the points of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Broad Reach
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. For many sailing craft 45° on either side of the wind is a ''no-go'' zone, where a sail is unable to mobilize power from the wind. Sailing on a course as close to the wind as possible—approximately 45°—is termed ''beating'', a point of sail when the sails are ''close-hauled''. At 90° off the wind, a craft is on a ''beam reach''. The point of sail between beating and a beam reach is called a ''close reach''. At 135° off the wind, a craft is on a ''broad reach''. At 180° off the wind (sailing in the same direction as the wind), a craft is ''running downwind''. A given point of sail (beating, close reach, beam reach, broad reach, and running downwind) is defined in reference to the true wind—the wind felt by a stationary observ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. For many sailing craft 45° on either side of the wind is a ''no-go'' zone, where a sail is unable to mobilize power from the wind. Sailing on a course as close to the wind as possible—approximately 45°—is termed ''beating'', a point of sail when the sails are ''close-hauled''. At 90° off the wind, a craft is on a ''beam reach''. The point of sail between beating and a beam reach is called a ''close reach''. At 135° off the wind, a craft is on a ''broad reach''. At 180° off the wind (sailing in the same direction as the wind), a craft is ''running downwind''. A given point of sail (beating, close reach, beam reach, broad reach, and running downwind) is defined in reference to the true wind—the wind felt by a stationary observe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lift (force)
A fluid flowing around an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it can act in any direction at right angles to the flow. If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force. Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatic lift or buoyancy, in which an internal fluid is lighter than the surrounding fluid, does not require movement and is used by balloons, blimps, dirigibles, boats, and submarines. Planing lift, in which only the lower portion of the body is immersed in a liquid flow, is used by motorboats, surfboards, windsurfers, sailboats, and water-skis. Overview A fluid flowing arou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 moving. Angle of attack is the angle between the body's reference line and the oncoming flow. This article focuses on the most common application, the angle of attack of a wing or airfoil moving through air. In aerodynamics, angle of attack specifies the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. Since a wing can have twist, a chord line of the whole wing may not be definable, so an alternate reference line is simply defined. Often, the chord line of the root of the wing is chosen as the reference line. Another choice is to use a horizontal line on the fuselage as the reference line (and also as the longitudinal axis). Some aut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 of the apparent wind'' is the vector sum of the ''velocity of the headwind'' (which is the velocity a moving object would experience in still air) plus the ''velocity of the true wind''. The headwind is the additive inverse of the object's velocity; therefore, the ''velocity of the apparent wind'' can also be defined as a vector sum of the ''velocity of the true wind'' minus the ''velocity of the object''. Apparent wind in sailing In sailing, ''apparent wind'' is the speed and direction of wind indicated by a wind instrument ( anemometer) on a ''moving'' craft (on water, land or ice) in undisturbed air. It is composed of the ''combined'' speeds and directions of the craft and wind observed by a ''stationary'' wind instrument—the ''true ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Close-hauled
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. For many sailing craft 45° on either side of the wind is a ''no-go'' zone, where a sail is unable to mobilize power from the wind. Sailing on a course as close to the wind as possible—approximately 45°—is termed ''beating'', a point of sail when the sails are ''close-hauled''. At 90° off the wind, a craft is on a ''beam reach''. The point of sail between beating and a beam reach is called a ''close reach''. At 135° off the wind, a craft is on a ''broad reach''. At 180° off the wind (sailing in the same direction as the wind), a craft is ''running downwind''. A given point of sail (beating, close reach, beam reach, broad reach, and running downwind) is defined in reference to the true wind—the wind felt by a stationary observe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. For many sailing craft 45° on either side of the wind is a ''no-go'' zone, where a sail is unable to mobilize power from the wind. Sailing on a course as close to the wind as possible—approximately 45°—is termed ''beating'', a point of sail when the sails are ''close-hauled''. At 90° off the wind, a craft is on a ''beam reach''. The point of sail between beating and a beam reach is called a ''close reach''. At 135° off the wind, a craft is on a ''broad reach''. At 180° off the wind (sailing in the same direction as the wind), a craft is ''running downwind''. A given point of sail (beating, close reach, beam reach, broad reach, and running downwind) is defined in reference to the true wind—the wind felt by a stationary observe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 full sail area is termed ''shaking out'' a reef. Whereas fore-and-aft rigged vessels store the unused portion of the sail on a boom, below the sail, square-rigged vessels stow the unused portion on a spar, above the sail. Reefing may occur by rolling the sail around its luff or foot, either on a rotating stay or within a spar. Fore-and-aft rigs Sails may have built-in alternative attachment points that allow their area to be reduced. In a mainsail, pairs of grommets, called reefing tacks, reefing clews, or reefing cringles may be installed in the sail; a cruising boat will typically have two to three pairs. Pulling these points down to the boom forms a new tack and clew, reducing the sail's area. Using the pair of grommets closest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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