A sail is any type of surface intended to generate thrust by being placed in a wind—in essence a vertically-oriented wing. Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws. Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) WING "ESPN 1410" is a commercial AM radio station in Dayton Ohio operating with 5000 watts at 1410 kHz with studios offices and transmitter located on David Sails are used in sailing. Sailing is the art of controlling a Sailing vessel. By changing the Rigging, Rudder and dagger or centre board a Sailor manages the force
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Use of sails
Sails are primarily used on the water by sailing ships and sail boats as a propulsion system. Sailing ship is now used to refer to any large Wind -powered Vessel. In some cases less is more The purpose of this article is to give an overview Marine propulsion is the act of moving a floating object over or through water For purposes of commerce, sails have been greatly superseded by other forms of propulsion, such as the internal combustion engine. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a For recreation, however, sailing vessels remain popular. Recreation or fun is the expenditure of time in a manner designed for therapeutic refreshment of one's Body or Mind.
The most familiar type of sailboat, a small pleasure yacht, usually has a sail-plan called a sloop. A yacht is a recreational boat It designates two rather different classes of Watercraft, sailing and power yachts A sail-plan is a set of drawings usually prepared by a naval architect. For the military definition of sloop see Sloop-of-war. For the open learning project see SLOOP Project. This has two sails in a fore-and-aft arrangement: the mainsail and the jib. A mainsail is the most important sail raised from the main (or only mast of a sailing vessel A jib (also spelled jibb) is a triangular Staysail set ahead of the foremost mast of a sailing boat
The mainsail extends aftward and is secured the whole length of its edges to the mast and to a boom also hung from the mast. The mast of a sailing ship is a tall vertical or near vertical Spar, or arrangement of Spars which supports the Sails Large ships have several masts In Sailing, a boom is a Spar (pole along the foot (bottom of a Fore and aft rigged Sail, that greatly improves control of the angle The sails of tall ships are attached to wooden timbers or "spars". In Sailing, a spar is also know as a round pole of wood or Metal used on a Sailing ship.
The jib is secured along its leading edge to a forestay (strong wire) strung from the top of the mast to the bowsprit on the bow (nose) of the boat. A jib (also spelled jibb) is a triangular Staysail set ahead of the foremost mast of a sailing boat On a Sailing vessel a forestay, sometimes just called a stay is a piece of Standing rigging which keeps a mast from falling backwards The bowsprit, or boltsprit, of a Sailing vessel is a pole extending forward from the vessel's prow A genoa is also used on some boats. The genoa or jenny was originally referred to as the 'overlapping jib' or the Genoa jib, being named after the city of Genoa as explained below It is a type of jib that is larger, and cut so that it is fuller than an ordinary jib.
Fore-and-aft sails can be switched from one side of the boat to the other in order to provide propulsion as the sailboat changes direction relative to the wind. When the boat's stern crosses the wind, this is called jibing; when the bow crosses the wind, it is called tacking. A jibe or gybe is a sailing maneuver where a Sailing vessel turns its Stern through the wind such that the wind direction changes from one side of the Tacking repeatedly from port to starboard and/or vice versa, called "beating", is done in order to allow the boat to follow a course into the wind.
A primary feature of a properly designed sail is an amount of "draft", caused by curvature of the surface of the sail. In nautical parlance the draft or draught of a Sail is a degree of Curvature in a horizontal cross-section When the leading edge of a sail is oriented into the wind, the correct curvature helps maximise lift while minimising turbulence and drag, much like the carefully designed curves of aircraft wings. Modern sails are manufactured with a combination of broadseaming and non-stretch fabric (ref New technology below). Broadseam is a term particular to the making of a Sail. The panels that make up the sections of a sail are cut with curves on the connecting edges or seams. The former adds draft, while the latter allows the sail to keep a constant shape as the wind pressure increases. The draft of the sail can be reduced in stronger winds by use of a cunningham and outhaul, and also by bending the mast and increasing the downward pressure of the boom by use of a boom vang. In Sailing, a cunningham or cunningham's eye is a type of Downhaul used on a Bermuda rigged sailboat to change the shape of a sail An outhaul is a line which is part of the Running rigging of a Sailboat, which is used to extend a Sail, and control the shape of the curve of the A boom vang (US or kicking strap (UK is a line or piston system on a Sailboat used to exert downward force on the boom and thus control the shape
Other sail powered machines include ice yachts, windmills, kites, signs, hang gliders, electric generators, windsurfers , and land sailing vehicles. A machine is any device that uses Energy to perform some activity An ice boat (often spelled as "iceboat" once called an ice scooter) is a Boat or purpose-built framework similar in appearance to a Sail boat A windmill is a machine that is powered by the energy of the wind A kite is a flying tethered object that depends upon the tension of a tethering system History See also History of hang gliding Summary: Hang gliding existed in China perhaps by the 4th century AD according to the writing of the Windsurfing is a surface water sport using a windsurf board also commonly called a sailboard usually two to five meters long and powered by a single sail Land sailing, also known as sand yachting or land yachting, is the act of moving across land in a wheeled Vehicle powered by Wind
Sail construction is governed by the science of aerodynamics.
Sail aerodynamics
Sails propel the boat in one of two ways. When the boat is going in the direction of the wind (i. e. downwind - see Points of sail), the sails may be set merely to trap the air as it flows by. Points of sail describes a sailing boat's course in relation to the wind direction Sails acting in this way are aerodynamically stalled. For other uses see Stall. In Aerodynamics, a stall is a sudden reduction in the lift forces generated by an Airfoil In stronger winds, turbulence created behind stalled sails can lead to aerodynamic instability, which in turn can manifest as increased downwind rolling of the boat. Spinnakers and square-rigged sails are often trimmed so that their upper edges become leading edges and they operate as airfoils again, but with airflow directed more or less vertically downwards. This mode of trim also provides the boat with some actual lift and may reduce both wetted area and the risk of 'digging in' to waves.
The other way sails propel the boat occurs when the boat is traveling across or into the wind. In these situations, the sails propel the boat by redirecting the wind coming in from the side towards the rear. In accordance with the law of conservation of momentum, air is redirected backwards, making the boat go forward. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product This driving force is called lift although it acts largely horizontally. In the context of a Fluid flow relative to a body the lift force is the component of the Aerodynamic force that is Perpendicular to the flow
On a sailing boat, a keel or centreboard helps to prevent the boat from moving sideways. Dinghy sailing is the activity of Sailing small boats by using (1 the Sails and (2 underwater foils ( Daggerboard or Centreboard In boats and ships keel can refer to either of two parts a structural element or a hydrodynamic element The shape of the keel has a much smaller cross section in the fore and aft axis and a much larger cross section on the athwart axis (across the beam of the boat). The resistance to motion along the smallest cross section is low while resistance to motion across the large cross section is high, so the boat moves forward rather than sideways. In other words it is easier for the sail to push the boat forward rather than sideways. However, there is always a small amount of sideways motion, or "leeway".
Forces across the boat are resolved by balancing the sideways force from the sail with the sideways resistance of the keel or centerboard. Also, if the boat heels, there are restoring forces due to the shape of the hull and the mass of the ballast in the keel being raised against gravity. Forward forces are balanced by velocity through the water and friction between the hull, keel and the water.
Parts of the sail
The lower edge of a triangular sail is called the "foot" of the sail, while the upper point is known as the "head". The lower two points of the sail, on either end of the foot, are called the "tack" (forward) and "clew" (aft). The forward edge of the sail is called the "luff" (from which derives the term "luffing", a rippling of the sail when the angle of the wind fails to maintain a good aerodynamic shape near the luff). The aft edge of a sail is called the "leech".
Modern sails are designed such that the warp and the weft of the sailcloth are oriented parallel to the luff and foot of the sail. In Weaving, the warp is the set of lengthwise Yarns through which the Weft is woven WEFT Champaign 901FM is a Community radio station in Champaign Illinois, founded in 1981 and owned by Prairie Air Inc This places the most stretchable axis of the cloth along the diagonal axis (parallel to the leech), and makes it possible for sailors to reduce the draft of the sail by tensioning the sail, mast and boom in various ways.
Often tell-tales, small pieces of yarn, are attached to the sail. A tell-tale is a reference indicator or a sign that clearly signals that something else is true or is about to happen They are used as a guide when trimming the sail.
An alternative approach to sail design is that used in Junks, originally an oriental design. -HK CityHall Seaview 51217 5png|thumb|300px|A modern junk in Hong Kong]]A junk is a Chinese sailing vessel. It uses horizontal sail curving to produce an efficient and easily controlled sail-plan. [1].
Sail types
Modern sails can be classified into three main categories: Mainsail, Headsail, and Spinnaker or downwind sail (also termed Kite). A mainsail is the most important sail raised from the main (or only mast of a sailing vessel A headsail of a Sailing vessel is any Sail set forward of the foremost mast. A spinnaker is a special type of Sail that is designed specifically for Sailing off the wind from a reaching course to a downwind i Special-purpose sails are often a variation of the three main categories. Most modern yachts including bermuda rig, ketch and yawl boats have a sail "inventory" which usually includes more than one of these types of sails. The term Bermuda rig refers to a configuration of mast and Rigging for a type of Sailboat and is also known as a Marconi rig; this is the typical A ketch is a Sailing Craft with two masts: a main mast and a shorter Mizzen mast abaft (rearward of the main mast YAWL (Yet Another Workflow Language is a Workflow language based on the Workflow patterns. Although the mainsail is “permanently” hoisted while sailing, headsails and spinnakers can be changed depending on the particular weather conditions to allow better handling and speed.
Mainsails as the name implies are the main element of the sailplan. A "motor" as well as a rudder for the boat, mainsails can be as simple as a traditional triangle-shaped, cross-cut sail (see Sail Construction below). In most cases, the mainsail isn’t changed while sailing although there are mechanisms to reduce its surface if the wind is very strong (a technique called reefing). Reefing is a sailing manoeuvre intended to reduce the area of a Sail on a Sailboat or Sailing ship, which can improve the ship's stability and reduce In extreme weather, a mainsail can be folded and a trysail hoisted to allow steerage without endangering the boat. A trysail is small Fore-and-aft Sail used in very high winds or in storms to maintain control to avoid ship damage and to keep the bow to the wind
Headsails are the main driving sails when going upwind (sailing towards the wind). There are many types of headsails with Genoa and Jib being the most commonly used. The genoa or jenny was originally referred to as the 'overlapping jib' or the Genoa jib, being named after the city of Genoa as explained below A jib (also spelled jibb) is a triangular Staysail set ahead of the foremost mast of a sailing boat Both these types have different subtypes depending on their intended use. Headsails are usually classified according to their weight (that is, the relative weight of the sailcloth used) and size or total area of the sail. A common classification is numbering from 1 to 3 (larger to smaller) with a description of the use for example: #1 Heavy or #1 Medium/Light. Special types of headsails include the Gennaker (also named Code 0 by some sailmakers), the drifter (a type of Genoa that is used like an asymmetrical spinnaker), the screecher (essentially a large Genoa), the windseeker and storm jib. A gennaker is a recently-developed Sail used when Sailing Downwind; it can be described as a cross between Certain Genoas and Jibs also have battens which assist in maintaining an optimal shape for the sail.
Spinnakers are used for reaching and running (downwind sailing). They are very light and have a balloon-like shape. As with headsails there are many types of spinnakers depending on the shape, area and cloth weight. Symmetrical spinnakers are most efficient on runs and dead runs (sailing with wind coming directly from behind) while asymmetric spinnakers are very efficient in reaching (the wind coming from the rear but at an angle to the boat or from the side).
Sail construction
A sail might look flat when lying on the floor but once it's hoisted, it becomes a three-dimensional, curved surface, in essence an airfoil. An airfoil (in American English) or aerofoil (in British English) is the shape of a Wing or blade (of a Propeller, rotor In order for a sail to be "built", it has to be designed in a number of elements (or panels) which are cut and sewn together to form the foil. In older days, this was rightfully considered an art which was later complemented (and arguably overshadowed) by technology. With the advent of computers, sail manufacturers were able to model their sails using special computer-aided design (CAD) programs and directly feed the data to very accurate laser plotters/cutters which cut the panels from rolls of sail cloth, replacing the traditional manual process (scissors).
The key features that distinguish a "fast" from a "slow" sail are its shape related to the particular boat and rig and its ability to consistently maintain that shape. These two features rely mostly on the design of the sail (the way that the panels are placed with one another) and the sail cloth used.
The traditional parallel-panel (cross-cut) gave way to more complex (radial) designs where the panels have different shapes for the top, mid, and lower sections of the sail depending on pressure of the air caused by its flow over the sail surface. Again aided by CAD and special modelling software the sailmakers use cloths of different weight, placing heavier cloth panels where there is more stress and lighter cloth where there is less to make savings in weight.
Older fabrics (especially cotton and low budget synthetic), have the tendency to stretch with wind pressure which results in distorted and consequently inefficient sail shapes. Sails have been made from Cloth for all of recorded history Typically sails were made from Flax ( Linen) Hemp or Cotton in various Moreover, the cloth itself is heavy which adds to the inefficiency. Synthetic materials such as Nylon and Dacron were followed by advanced sail cloths made from exotic material yarns such as Aramid (e. Overview Nylon is a Thermoplastic silky material first used commercially in a nylon- Bristled Toothbrush (1938 followed more famously by Uses PET can be semi-rigid to rigid depending on its thickness and is very lightweight Aramid fibers are a class of heat-resistant and strong Synthetic fibers They are used in aerospace and military applications for ballistic rated body armor g. Twaron, Technora or kevlar), carbon fiber, HMPE (e.g. Spectra/Dyneema), Zylon (PBO) and Vectran (see also Sailcloth). Twaron is the brandname of Teijin Aramid for a para-aramid. History Twaron is a heat-resistant and strong Synthetic fiber developed Technora is the brandname of Teijin for a aromatic copolyamid. Kevlar is the registered Trademark for a light strong para-aramid Synthetic fiber, related to other Aramids such as Nomex and Ultra high molecular weight polyethylene ( UHMWPE) also known as high-modulus polyethylene ( HMPE) or high-performance polyethylene ( HPPE Zylon is a Trademarked name for a range of Thermoset Polyurethane Synthetic polymer materials manufactured by the Toyobo Corporation Vectran is a manufactured fibre spun from a Liquid crystal polymer created by Celanese Acetate LLC and now manufactured by Kuraray Co Sails have been made from Cloth for all of recorded history Typically sails were made from Flax ( Linen) Hemp or Cotton in various These materials were a breakthrough in sail technology as they provided the raw material in the manufacture of low-stretch, low-weight and long-life sail cloths. Manufacturers were able to use different weights of yarn to weave cloths with exceptional properties.
Once the panels are sewn together, the sailmakers complete the sail by placing the finishing elements such as the leech and foot lines, protective patches in the areas where the sail will scrape against hardware (stanchions, spreaders), steel rings and straps at the tack and clew, cleats, batten pockets (if required) and sail numbers.
Lamination
Woven cloth or ribbons of high tensile fabric inserts can be "sandwiched" between two films of Mylar and placed in special ovens under pressure to bond into a single body, a process called lamination. Biaxially-oriented Polyethylene terephthalate (boPET Polyester film is used for its high Tensile strength, Chemical and dimensional Stability A laminate is a material constructed by uniting two or more layers of material together The inserts provide the strength and the mylar the continuity and wind resistance. An alternative method is to sandwich a sheet of Mylar between two layers of woven cloth. The latter process is popular when using cloth with high strength and UV tolerance, but an open weave. In the latter process the cloth protects the more brittle mylar. A more complex sail may combine the processes. See also sailcloth. Sails have been made from Cloth for all of recorded history Typically sails were made from Flax ( Linen) Hemp or Cotton in various
History of sails
Sails were invented in the ancient age, and were the most important source of propulsion during the age of sail. "Ancient" redirects here For other uses see Ancient_(disambiguation. The Age of Sail was the period in which International trade and Naval warfare were dominated by Sailing Ships lasting from the 16th to the mid
Advances in sail materials and manufacture
In addition to advances in the exotic materials and consequent cloths themselves, manufacturers have also progressed the manufacturing process with the creation of glued and molded sails.
Glued sails are regular paneled sails but instead of sewing the pieces together, the sailmaker uses a special, ultra-strong polymer glue which bonds through the use of ultrasound. Not to be confused with Supersonic. Ultrasound is cyclic Sound pressure with a Frequency greater than the upper In molding, a curved mold is designed and created in the optimum (three dimensional) shape of the sail that the sailmaker wants to produce. A film of Mylar is placed on the mold and a special gantry hovers over the film laying the yarns based on instructions of a computer that has the model of the sail. Biaxially-oriented Polyethylene terephthalate (boPET Polyester film is used for its high Tensile strength, Chemical and dimensional Stability Once this is done, a second sheet of Mylar film is placed on top and the whole mold (with the sail) is placed in a vacuum oven which causes the materials to bond (curing). Curing is a term in Polymer chemistry and Process engineering that refers to the toughening or hardening of a Polymer material by Cross-linking The result is a smooth sail which is lighter and has a wider effective wind range (the minimum and maximum wind speed that the sail can withstand and be effective).
Molding initially targeted high-end competition boats because of the costs of the sails produced but has steadily moved on to cover cruising yachts although panelled (woven) sails account for the majority of sails (racing or recreational) used around the world. The concept of molded sails was introduced by Sobstad Sails with its Genesis line but did not maintain consistent product performance. North Sails introduced its successful 3DL product line which also resulted in a legal battle with Sobstad. Variations of the molding sailmaking process are used by other leading sail manufacturers such as Quantum with the Fusion-M line and Doyle Sailmakers with the Stratis line and Dimension-Polyant with D4 which is available to all sailmakers. Other sailmakers are producing lines which make use of molding concepts although not necessarily the production process itself such as the UK-Halsey TapeDrive line.
Alternatives To Traditional Sails
Kites are currently being tested as an alternative to traditional sail technology. MS Beluga Skysails is the first ship [1] to use this technology which will has the potential to provide supplemental propulsion to both ships and boats [2]. Kite power The kite has an initial area of which should reduce fuel consumption by 20% and can be unfurled to in order to save about 30%
See also
Types of sails |
References
- ^ "Kite to pull ship across Atlantic", BBC, 2008-01-22. Sailing is the art of controlling a Sailing vessel. By changing the Rigging, Rudder and dagger or centre board a Sailor manages the force Sails have been made from Cloth for all of recorded history Typically sails were made from Flax ( Linen) Hemp or Cotton in various This article is about yacht cruising For cruising on cruise liners see the article Cruise ship. Points of sail describes a sailing boat's course in relation to the wind direction A sail-plan is a set of drawings usually prepared by a naval architect. Rigging (from Anglo-Saxon wrigan or wringing, "to clothe" is on Sailboats and Sailing ships the collection of WING "ESPN 1410" is a commercial AM radio station in Dayton Ohio operating with 5000 watts at 1410 kHz with studios offices and transmitter located on David A rudder is a device used to steer a Ship, Boat, Submarine, Hovercraft, or other conveyance that move through a fluid (generally air or fin is a surface used to produce lift and Thrust or to steer while traveling in Water, air or other Fluid media Solar sails (also called light sails or photon sails, especially when they use Light sources other than the Sun) are a proposed form of Sail twist is a phenomenon in Sailing where the head of the Sail is at a different Angle of attack from the foot of the sail in order to change the Marine canvas refers to the field of work concerned with the Design and Fabrication of Functional Canvas products (usually custom Baggywrinkle is a soft covering for cables (or any other obstructions to reduce Sail chafe. A kite is a flying tethered object that depends upon the tension of a tethering system History See also History of hang gliding Summary: Hang gliding existed in China perhaps by the 4th century AD according to the writing of the A lugger is a type of small Sailing vessel setting lugsails on two or more masts and perhaps lug Topsails. Gaff rig is a Sailing rig (configuration of sails in which the Sail is four-cornered Fore-and-aft rigged controlled at its peak and usually A royal is a small Sail flown immediately above the topgallant on Square rigged Sailing ships It was originally called the "topgallant royal" A wingsail is a form of marine propulsion similar to conventional sails A turbosail is a naval propulsion system invented by Jacques-Yves Cousteau and used on the ''Alcyone''. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 565 - Eutychius is deposed as Patriarch of Constantinople by John Scholasticus. Retrieved on 2008-01-22. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 565 - Eutychius is deposed as Patriarch of Constantinople by John Scholasticus.
- ^ A Comprehensive Look at SkySails and Green Propulsion.
External links
- Sailboats database: sailing yacht data sheets all over the world
- Sail Design Software
- The quest for the perfect sailshape
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