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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 between the leading edge (luff) and trailing edge (leech) with that of the boom. Some twist is desirable, but too much can induce weather helm or ruin the slot between the mainsail and jib. Three sail shape controls which control the leech tension, and therefore sail twist, are the mainsheet, the boom vang and the traveler. The mainsheet pulls the boom (and therefore the foot of the sail) primarily inwards at lower points of sail and downwards at higher points of sail. Manipulation of the traveler can counteract this because it always pulls the boom laterally. The vang on the other hand does the opposite, it always changes the height of the boom. Computer cut sails can produce the amount of twist specified by the sailmaker, and in different c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sailing
Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, windsurfer, or kitesurfer), on ''ice'' (iceboat) or on ''land'' (land yacht) over a chosen course, which is often part of a larger plan of navigation. From prehistory until the second half of the 19th century, sailing craft were the primary means of maritime trade and transportation; exploration across the seas and oceans was reliant on sail for anything other than the shortest distances. Naval power in this period used sail to varying degrees depending on the current technology, culminating in the gun-armed sailing warships of the Age of Sail. Sail was slowly replaced by steam as the method of propulsion for ships over the latter part of the 19th century – seeing a gradual improvement in the technology of steam through a number of stepwise developments. Steam allowed scheduled services that ran at higher average speeds than sail ... [...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 air p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angle Of Incidence (aerodynamics)
On fixed-wing aircraft, the angle of incidence (sometimes referred to as the ''mounting angle'' or ''setting angle'') is the angle between the chord line of the wing where the wing is mounted to the fuselage, and a reference axis along the fuselage (often the direction of minimum drag, or where applicable, the longitudinal axis). The angle of incidence is fixed in the design of the aircraft, and with rare exceptions, cannot be varied in flight. The term can also be applied to horizontal surfaces in general (such as canards or horizontal stabilizers) for the angle they make relative the longitudinal axis of the fuselage. The figure to the right shows a side view of an airplane. The extended chord line of the wing root (red line) makes an angle with the longitudinal axis (roll axis) of the aircraft (blue line). Wings are typically mounted at a small positive angle of incidence, to allow the fuselage to have a low angle with the airflow in cruising flight. Angles of incidence o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lift Distribution
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 around ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boom (sailing)
In sailing, a boom is a spar (pole), along the of a fore and aft rigged sail, that greatly improves control of the angle and shape of the sail. The primary action of the boom is to keep the ''foot'' flatter when the sail angle is away from the centerline of the boat. The boom also serves as an attachment point for more sophisticated control lines. Because of the improved sail control it is rare to find a non-headsail without a boom, but lateen sails, for instance, are loose-footed. In some modern applications, the sail is rolled up into the boom for storage or reefing (shortening sail). Boom attachment The forward end of the boom attaches to a mast just below the sail, with a joint called the gooseneck. The gooseneck pivots allowing the other end of the boom to move freely. The clew (back corner) of the sail attaches to the free end of the boom. The entire ''foot'' of the sail may be attached to the boom or just the clew. If the ''foot'' is not attached to the boom, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weather Helm
Weather helm is the tendency of sailing vessels to turn towards the source of wind, creating an unbalanced helm that requires pulling the tiller to windward (i.e. 'to weather') in order to counteract the effect. Weather helm is the opposite of lee helm. It is generally less troublesome than lee helm. Overview Weather helm is the result of a leeward and aft shift of a vessel's vector center of effort (the direction to which the force generated by the sails is pushing). This shift is caused by excess pressure on the mainsail, which overpowers the windward lateral resistance generated by the jib (or other head sail) and keel or centerboard. This results in an imbalance of force at the stern from windward, and the craft pivots about the center of drag (often near the center of the keel or centerboard), causing the bow to drive windward. Weather helm does not only result from an overpowered main; when a vessel is heeling to leeward, the aft component of keel drag is moved to windwar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 is normally attached to a boom. (In extremely heavy weather, the mainsail may be lowered, and a much smaller trysail hoisted in its place). Historical fore-and-aft rigs used a four-sided gaff rigged mainsail, sometimes setting a gaff topsail above it. Whereas once the mainsail was typically the largest sail, today the mainsail may be smaller than the jib or genoa; Prout catamarans typically have a mainmast stepped further aft than in a standard sloop, so that the mainsail is much smaller than the foresail. Bermuda rig The modern Bermuda rig uses a triangular mainsail aft of the mast, closely coordinated with a jib for sailing upwind. A large overlapping jib or genoa is often larger than the mainsail. In downwind conditions (with t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mainsheet
In sailing, a sheet is a line (rope, Cable-laid, cable or chain) used to control the movable corner(s) (Sail components#Corners, clews) of a sail. Terminology In nautical usage the term "sheet" is applied to a line or chain attached to the lower corners of a sail for the purpose of extension or change of direction. The connection in derivation with the root "shoot" is more clearly seen in "sheet-anchor", one that is kept in reserve, to be "shot" in case of emergency. Fore-and-aft rigs Fore-and-aft rigs comprise the vast majority of sailing vessels in use today, including effectively all dinghy, dinghies and yachts. The sheet on a fore-and-aft sail controls the angle of the sail to the wind, and should be adjusted to keep the sail just filled. Most smaller boats use the Bermuda rig, which has two or three sets of sheets: * The mainsheet is attached to the boom, and is used to control the mainsail. In a rig with no boom on the mainsail, the mainsheet would attach directly to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boom Vang
A boom vang (US) or kicking strap (UK) (often shortened to "vang" or "kicker") is a line or piston system on a sailboat used to exert downward force on the boom and thus control the shape of the sail. The Collins English Dictionary defines it as "A rope or tackle extended from the boom of a fore-and-aft mainsail to a deck fitting of a vessel when running, in order to keep the boom from riding up". The vang typically runs from the base of the mast to the boom. Due to the great force necessary to change the height of the boom while a boat is under sail, a line-based boom vang usually includes some sort of a pulley system. Hydraulic piston vangs are used on larger sailboats and controlled by manual or electric hydraulic pumps. By controlling leech tension, the boom vang is one way of controlling sail twist. The boom vang may also be used to flatten the mainsail on dinghies. On small sailboats and some cruising sailboats a vang may be omitted. If a vang is not installed, then th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Traveller
A traveller is a part of the rigging of a boat or ship that provides a moving attachment point for a rope, sail or yard to a fixed part of the vessel. It may take the form of anything from a simple ring on a metal bar or a spar to, especially in a modern yacht, a more complex "car" – a component with bearing-mounted wheels running on a shaped aluminium extrusion. There are three common examples of the use of a traveller. The sheet of a sail is attached to a traveller on the horse, allowing the sail's clew to be positioned to leeward on each tack, thereby giving a more aerodynamically efficient position of the sail. A jib may be attached to a bowsprit with a traveller. This allows the sail to be set and handed without having to go out onto the bowsprit. Lastly, the yard of a lugsail is usually attached to the mast using a traveller. This often consists of a metal ring around the mast with a hook above and below the ring for, respectively, the halyard and the yard to fasten. A tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sailmaker
A sailmaker makes and repairs sails for sailboats, kites, hang gliders, wind art, architectural sails, or other structures using sails. A sailmaker typically works on shore in a sail loft; the sail loft has other sailmakers. Large ocean-going sailing ships often had sailmakers in the crew. The sailmaker maintained and repaired sails. This required knowledge of the sailmaker's craft and the tools of the sailmakers loft on shore. Today, one of a sailmaker's important jobs is to teach people how to set and trim their sails to get the most out of them. Sometimes a sailmaker will accompany the client out on the water and adjust the sails. The modern sailmaker uses computer-aided design and manufacturing tools. Computer graphics allow the sailmaker to produce a "lines drawing" of the sail. Once the design is complete, the sailmaker can now use a low-power laser to cut the material to the exact shape. Broadseam CFD Sailmakers have recently started using Computational fluid dynamics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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