1976 July Independence Day Regatta Philadelphia 2 pair 2nd place
Because there are several alternatives offered to the existing title, I thought that perhaps a ranked-choice poll would help identify a consensus in this matter, in light of the discussion above. Accordingly, I invite each of you, who has weighed in so far, to rank your preference among the alternatives. I would propose to assign a Borda count score to each of your rankings. So, out of four choices, your first choice would score 4-1= 3 points; your fourth choice would score 4-4 = 0 points. Here is a opportunity for each of you to score the alternatives in the order that they were offered (of course, you don't have to vote for an alternative that's unacceptable to you):[2]
Hopson Road
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For other uses, see Sailing (disambiguation). |
Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the water (sailing ship, sailboat, 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
A course defined with respect to the true wind direction is called a point of sail.
Conventional sailing craft cannot derive power from sails on a point of sail that is too close into the wind. On a given point of sail, the sailor adjusts the alignment of each sail with respect to the apparent wind direction (as perceived on the craft) to mobilize the power of the wind. The forces transmitted via the sails are resisted by forces from the hull, keel, and rudder of a sailing craft, by forces from skate runners of an iceboat, or by forces from wheels of a land sailing craft to allow steering the course.
In the 21st century, most sailing represents a form of recreation or sport. Recreational sailing or yachting can be divided into racing and cruising. Cruising can include extended offshore and ocean-crossing trips, coastal sailing within sight of land, and daysailing.
From the 16th century until the middle of the 19th century, sailing ships were the primary means for marine commerce and naval warfare, this period is known as Age of Sail.
Further information: Maritime history and Sailing ship § History |
Throughout history sailing has been a key form of propulsion that allowed greater mobility than travel over land, whether for exploration, trade, transport, or warfare, and that increased the capacity for fishing, compared to that from shore.
Early square rigs generally could not sail much closer than 80° to the wind, whereas early fore-and-aft rigs could sail as close as 60–75° off the wind.[3] Later square-rigged vessels too were able to sail to windward, and became the standard for European ships through the Age of Discovery when vessels ventured around Africa to India, to the Americas and around the world.[4] Sailing ships became longer and faster over time, with ship-rigged vessels carrying taller masts with more square sails. The Age of Sail (1570–1870) reached its peak in the 18th and 19th centuries with merchant sailing ships that were able to travel at speeds that exceeded those of the newly introduced steamships.
Austronesian peoples sailed from what is now Southern China and Taiwan with of catamarans or vessels outriggers,[5] and crab claw sails,[6] which enabled the Austronesian Expansion at around 3000 to 1500 BCE into the islands of Maritime Southeast Asia, and thence to Micronesia, Island Melanesia, Polynesia, and Madagascar.[7] They traveled vast distances of open ocean in outrigger canoes using navigation methods such as stick charts.[8][9]
By the time of the Age of Discovery—starting in the 15th century—square-rigged, multi-masted vessels were the norm and were guided by navigation techniques that included the magnetic compass and making sightings of the sun and stars that allowed transoceanic voyages.[4]
During the Age of Discovery, sailing ships figured in European voyages around Africa to China and Japan; and across the Atlantic Ocean to North and South America. Later, sailing ships ventured into the Arctic to explore northern sea routes and assess natural resources. In the 18th and 19th centuries sailing vessels made hydrographic surveys to develop charts for navigation and, at times, carried scientists aboard as with the voyages of James Cook and the Second voyage of HMS Beagle with naturalist Charles Darwin.
In the early 1800s, fast blockade-running schooners and brigantines—Baltimore clippers—evolved into three-masted, typically ship-rigged sailing vessels with fine lines that enhanced speed, but lessened capacity for high-value cargo, like tea from China.[10] Masts were as high as 100 feet (30 m) and were able to achieve speeds of 19 knots (35 km/h), allowing for passages of up to 465 nautical miles (861 km) per 24 hours. Clippers yielded to bulkier, slower vessels, which became economically competitive in the mid 19th century.[11] Sail plans with just fore-and-aft sails (schooners), or a mixture of the two (brigantines, barques and barquentines) emerged.[4] Coastal top-sail schooners with a crew as small as two managing the sail handling became an efficient way to carry bulk cargo, since only the fore-sails required tending while tacking and steam-driven machinery was often available for raising the sails and the anchor.[12]
Iron-hulled sailing ships represented the final evolution of sailing ships at the end of the Age of Sail. They were built to carry bulk cargo for long distances in the nineteenth and early twentieth centuries.[13] They were the largest of merchant sailing ships, with three to five masts and square sails, as well as other sail plans. They carried bulk cargoes between continents. Iron-hulled sailing ships were mainly built from the 1870s to 1900, when steamships began to outpace them economically, due to their ability to keep a schedule regardless of the wind. Steel hulls also replaced iron hulls at around the same time. Even into the twentieth century, sailing ships could hold their own on transoceanic voyages such as Australia to Europe, since they did not require bunkerage for coal nor fresh water for steam, and they were faster than the early steamers, which usually could barely make 8 knots (15 km/h).[14] Ultimately, the steamships' independence from the wind and their ability to take shorter routes, passing through the Suez and Panama Canals, made sailing ships uneconomical.[15]
Further information: Sailing ship tactics |
Until the general adoption of carvel-built ships that relied on an internal skeleton structure to bear the weight of the ship and for gun ports to be cut in the side, sailing ships were just vehicles for delivering fighters to the enemy for engagement.[16] By 1500, gun ports allowed sailing vessels to sail alongside alongside an enemy vessel and fire a broadside of multiple cannon.[17] This development allowed for naval fleets to array themselves into a line of battle, whereby, warships would maintain their place in the line to engage the enemy in a parallel or perpendicular line.[18]
Recreational sailing can be divided into two categories, day-sailing, where one gets off the boat for the night, and cruising, where one stays aboard.
Day-sailing primarily affords experiencing the pleasure of sailing a boat. No destination is required. It is an opportunity to share the experience with others.[19] A variety of boats with no overnight accomations, ranging in size from 10 feet (3.0 m) to over 30 feet (9.1 m), may be regarded as day sailers.[20]
Cruising may be either near-shore or passage-making out of sight of land and entails the use of sailboats that support sustained overnight use.[21] Coastal cruising grounds include areas of the Mediterranean and Black Seas, Northern Europe, Western Europe and islands of the North Atlantic, West Africa and the islands of the South Atlantic, the Caribbean, and regions of North and Central America.[22] Passage-making under sail occurs on routes through oceans all over the world. Circular routes exist between the Americas and Europe, and between South Africa and South America. There are many routes from the Americas, Australia, New Zealand, and Asia to island destinations in the South Pacific. Some cruisers circumnavigate the globe.[23]
Main article: Sailing (sport) |
Sailing as a sport is organized on a hierarchical basis, starting at the yacht club level and reaching up into national and international federations. Sailboat racing is governed by World Sailing with most racing formats using the Racing Rules of Sailing.[24] It entails a variety of different disciplines, including:
Main article: Forces on sails |
The physics of sailing arises from a balance of forces between the wind powering the sailing craft as it passes over its sails and the resistance by the sailing craft against being blown off course, which is provided in the water by the keel, rudder, underwater foils and other elements of the underbody of a sailboat, on ice by the runners of an ice boat, or on land by the wheels of a sail-powered land vehicle.
Forces on sails depend on wind speed and direction and the speed and direction of the craft. 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 (90°) to the apparent wind. Depending on the alignment of the sail with the apparent wind (angle of attack), lift or drag may be the predominant propulsive component. Depending on the angle of attack of a set of sails with respect to the apparent wind, each sail is providing motive force to the sailing craft either from lift-dominant attached flow or drag-dominant separated flow. Additionally, sails may interact with one another to create forces that are different from the sum of the individual contributions of each sail, when used alone.
The term "velocity" refers both to speed and direction. As applied to wind, apparent wind velocity (VA) is the air velocity acting upon the leading edge of the most forward sail or as experienced by instrumentation or crew on a moving sailing craft. In nautical terminology, wind speeds are normally expressed in knots and wind angles in degrees. All sailing craft reach a constant forward velocity (VB) for a given true wind velocity (VT) and point of sail. The craft's point of sail affects its velocity for a given true wind velocity. Conventional sailing craft cannot derive power from the wind in a "no-go" zone that is approximately 40° to 50° away from the true wind, depending on the craft. Likewise, the directly downwind speed of all conventional sailing craft is limited to the true wind speed. As a sailboat sails further from the wind, the apparent wind becomes smaller and the lateral component becomes less; boat speed is highest on the beam reach. In order to act like an airfoil, the sail on a sailboat is sheeted further out as the course is further off the wind.[31] As an iceboat sails further from the wind, the apparent wind increases slightly and the boat speed is highest on the broad reach. In order to act like an airfoil, the sail on an iceboat is sheeted in for all three points of sail.[32]
Main articles: Lift (force) and Lift-induced drag |
Lift on a sail, acting as an airfoil, occurs in a direction perpendicular to the incident airstream (the apparent wind velocity for the head sail) and is a result of pressure differences between the windward and leeward surfaces and depends on angle of attack, sail shape, air density, and speed of the apparent wind. The lift force results from the average pressure on the windward surface of the sail being higher than the average pressure on the leeward side.[33] These pressure differences arise in conjunction with the curved air flow. As air follows a curved path along the windward side of a sail, there is a pressure gradient perpendicular to the flow direction with higher pressure on the outside of the curve and lower pressure on the inside. To generate lift, a sail must present an "angle of attack" between the chord line of the sail and the apparent wind velocity. Angle of attack is a function of both the craft's point of sail and how the sail is adjusted with respect to the apparent wind.[34]
As the lift generated by a sail increases, so does lift-induced drag, which together with parasitic drag constitute total drag, which acts in a direction parallel to the incident airstream. This occurs as the angle of attack increases with sail trim or change of course and causes the lift coefficient to increase up to the point of aerodynamic stall along with the lift-induced drag coefficient. At the onset of stall, lift is abruptly decreased, as is lift-induced drag. Sails with the apparent wind behind them (especially going downwind) operate in a stalled condition.[35]
Lift and drag are components of the total aerodynamic force on sail, which are resisted by forces in the water (for a boat) or on the traveled surface (for an ice boat or land sailing craft). Sails act in two basic modes; under the lift-predominant mode, the sail behaves in a manner analogous to a wing with airflow attached to both surfaces; under the drag-predominant mode, the sail acts in a manner analogous to a parachute with airflow in detached flow, eddying around the sail.
Sails allow progress of a sailing craft to windward, thanks to their ability to generate lift (and the craft's ability to resist the lateral forces that result). Each sail configuration has a characteristic coefficient of lift and attendant coefficient of drag, which can be determined experimentally and calculated theoretically. Sailing craft orient their sails with a favorable angle of attack between the entry point of the sail and the apparent wind even as their course changes. The ability to generate lift is limited by sailing too close to the wind when no effective angle of attack is available to generate lift (causing luffing) and sailing sufficiently off the wind that the sail cannot be oriented at a favorable angle of attack to prevent the sail from stalling with flow separation.
When sailing craft are on a course where the angle between the sail and the apparent wind (the angle of attack) exceeds the point of maximum lift, separation of flow occurs.[36] Drag increases and lift decreases with increasing angle of attack as the separation becomes progressively pronounced until the sail is perpendicular to the apparent wind, when lift becomes negligible and drag predominates. In addition to the sails used upwind, spinnakers provide area and curvature appropriate for sailing with separated flow on downwind points of sail, analogous to parachutes, which provide both lift and drag.[37]
Further information: Wind gradient § Sailing |
Wind speed increases with height above the surface; at the same time, wind speed may vary over short periods of time as gusts.
Wind shear affects sailing craft in motion by presenting a different wind speed and direction at different heights along the mast. Wind shear occurs because of friction above a water surface slowing the flow of air.[38] The ratio of wind at the surface to wind at a height above the surface varies by a power law with an exponent of 0.11-0.13 over the ocean. This means that a 5-m/s (≈10-knot) wind at 3 m above the water would be approximately 6 m/s (≈12 knots) at 15 m above the water. In hurricane-force winds with 40-m/s (≈78 knots) at the surface the speed at 15 m would be 49 m/s (≈95 knots).[39] This suggests that sails that reach higher above the surface can be subject to stronger wind forces that move the centre of effort on them higher above the surface and increase the heeling moment. Additionally, apparent wind direction moves aft with height above water, which may necessitate a corresponding twist in the shape of the sail to achieve attached flow with height.[40]
Gusts may be predicted by the same value that serves as an exponent for wind shear, serving as a gust factor. So, one can expect gusts to be about 1.5 times stronger than the prevailing wind speed (a 10-knot wind might gust up to 15 knots). This, combined with changes in wind direction suggest the degree to which a sailing craft must adjust sail angle to wind gusts on a given course.[41]
See also: High-performance sailing |
Waterborne sailing craft rely on the design of the hull and keel to provide minimal forward drag in opposition to the sails' propulsive power and maximum resistance to the sails' lateral forces. In modern sailboats, drag is minimized by control of the hull's shape (blunt or fine), appendages, and slipperiness. The keel or other underwater foils provide the lateral resistance to forces on the sails. Heeling increases both drag and the ability of the boat to track along its desired course. Wave generation for a displacement hull is another important limitation on boat speed.[42]
Drag due to its form is described by a prismatic coefficient, Cp = displaced volume of the vessel divided by waterline length times maximum displaced section area—the maximum value of Cp = 1.0 being for a constant displace cross section area, as would be found on a barge. For modern sailboats, values of 0.53 ≤ Cp ≤ 0.6 are likely because of the tapered shape of the submerged hull towards both ends. Reducing interior volume allows creating a finer hull with less drag. Because a keel or other underwater foil produces lift, it also produces drag, which increases as the boat heels. Wetted area of the hull affects total the amount of friction between the water and the hull's surface, creating another component of drag.[42]
Sailboats use some sort of underwater foil to generate lift that maintains the forward direction of the boat under sail. Whereas sails operate at angles of attack between 10° to 90° incident to the wind, underwater foils operate at angles of attack between 0° to 10° incident to the water passing by. Neither their angle of attack nor surface is adjustable (except for moveable foils) and they are never intentionally stalled. Heeling the vessel away from perpendicular into the water significantly degrades the boat's ability to point into the wind.[42]
For displacement hulls have are limited in speed at a level defined by the square roof of the boat's water line, the boat's hull speed. The addition of more power from sails or other source does not allow the vessel to go faster, it merely generates a wake with higher waves.[42] Planing sailboats transcend this limitation, whereby speed becomes a linear function of power.[43]
Sailing craft on foils, ice runners or wheels transcend the above consideration.[43]
The most basic control of the sail consists of setting its angle relative to the wind. The control line that accomplishes this is called a "sheet." If the sheet is too loose the sail will flap in the wind, an occurrence that is called "luffing." Optimum sail angle can be approximated by pulling the sheet in just so far as to make the luffing stop, or by using tell-tails – small ribbons or yarn attached each side of the sail that both stream horizontally to indicate a properly trimmed sail. Finer controls adjust the overall shape of the sail.
Two or more sails are frequently combined to maximize the smooth flow of air. The sails are adjusted to create a smooth laminar flow over the sail surfaces. This is called the "slot effect". The combined sails fit into an imaginary aerofoil outline, so that the most forward sails are more in line with the wind, whereas the more aft sails are more in line with the course followed. The combined efficiency of this sail plan is greater than the sum of each sail used in isolation.
More detailed aspects include specific control of the sail's shape, e.g.:
An important safety aspect of sailing is to adjust the amount of sail to suit the wind conditions. As the wind speed increases the crew should progressively reduce the amount of sail. On a small boat with only jib and mainsail this is done by furling the jib and by partially lowering the mainsail, a process called 'reefing the main'.
Reefing means reducing the area of a sail without actually changing it for a smaller sail. Ideally, reefing does not only result in a reduced sail area but also in a lower centre of effort from the sails, reducing the heeling moment and keeping the boat more upright.
There are three common methods of reefing the mainsail:
Mainsail furling systems have become increasingly popular on cruising yachts, as they can be operated shorthanded and from the cockpit, in most cases. However, the sail can become jammed in the mast or boom slot if not operated correctly. Mainsail furling is almost never used while racing because it results in a less efficient sail profile. The classical slab-reefing method is the most widely used. Mainsail furling has an additional disadvantage in that its complicated gear may somewhat increase weight aloft. However, as the size of the boat increases, the benefits of mainsail roller furling increase dramatically.
An old saying goes, "Once you've realized it's time to reef, it's too late". A similar one says, "The time to reef is when you first think about it".[61]
Hull trim is the adjustment of a boat's loading so as to change its fore-and-aft attitude in the water. In small boats, it is done by positioning the crew. In larger boats, the weight of a person has less effect on the hull trim, but it can be adjusted by shifting gear, fuel, water, or supplies. Different hull trim efforts are required for different kinds of boats and different conditions. Here are just a few examples: In a lightweight racing dinghy like a Thistle, the hull should be kept level, on its designed water line for best performance in all conditions. In many small boats, weight too far aft can cause drag by submerging the transom, especially in light to moderate winds. Weight too far forward can cause the bow to dig into the waves. In heavy winds, a boat with its bow too low may capsize by pitching forward over its bow (pitch-pole) or dive under the waves (submarine). On a run in heavy winds, the forces on the sails tend to drive a boat's bow down, so the crew weight is moved far aft.
When a ship or boat leans over to one side, from the action of waves or from the centrifugal force of a turn or under wind pressure or from the amount of exposed topsides, it is said to 'heel'. A sailing boat that is over-canvassed and therefore heeling excessively, may sail less efficiently. This is caused by factors such as wind gusts, crew ability, the point of sail, or hull size and design.
When a vessel is subject to a heeling force (such as wind pressure), vessel buoyancy and beam of the hull will counteract the heeling force. A weighted keel provides additional means to right the boat. In some high-performance racing yachts, water ballast or the angle of a canting keel can be changed to provide additional righting force to counteract heeling. The crew may move their personal weight to the high (upwind) side of the boat, this is called hiking, which also changes the centre of gravity and produces a righting lever to reduce the degree of heeling. Incidental benefits include faster vessel speed caused by more efficient action of the hull and sails. Other options to reduce heeling include reducing exposed sail area and efficiency of the sail setting and a variant of hiking called "trapezing". This can only be done if the vessel is designed for this, as in dinghy sailing. A sailor can (usually involuntarily) try turning upwind in gusts (it is known as rounding up). This can lead to difficulties in controlling the vessel if over-canvassed. Wind can be spilled from the sails by 'sheeting out', or loosening them. The number of sails, their size and shape can be altered. Raising the dinghy centreboard can reduce heeling by allowing more leeway.
The increasingly asymmetric underwater shape of the hull matching the increasing angle of heel may generate an increasing directional turning force into the wind. The sails' centre of effort will also increase this turning effect or force on the vessel's motion due to increasing lever effect with increased heeling which shows itself as increased human effort required to steer a straight course. Increased heeling reduces exposed sail area relative to the wind direction, so leading to an equilibrium state. As more heeling force causes more heel, weather helm may be experienced. This condition has a braking effect on the vessel but has the safety effect in that an excessively hard pressed boat will try and turn into the wind, therefore, reducing the forces on the sail. Small amounts (≤5 degrees) of weather helm are generally considered desirable because of the consequent aerofoil lift effect from the rudder. This aerofoil lift produces helpful motion to windward and the corollary of the reason why lee helm is dangerous. Lee helm, the opposite of weather helm, is generally considered to be dangerous because the vessel turns away from the wind when the helm is released, thus increasing forces on the sail at a time when the helmsperson is not in control.
Multihulls use flotation and/or weight positioned away from the centre line of the sailboat to counter the force of the wind. This is in contrast to heavy ballast that can account for up to 90% (in extreme cases like AC boats) of the weight of a monohull sailboat. In the case of a standard catamaran, there are two similarly-sized and -shaped slender hulls connected by beams, which are sometimes overlaid by a deck superstructure. Another catamaran variation is the proa. In the case of trimarans, which have an unballasted centre hull similar to a monohull, two smaller amas are situated parallel to the centre hull to resist the sideways force of the wind. The advantage of multihulled sailboats is that they do not suffer the performance penalty of having to carry heavy ballast, and their relatively lesser draft reduces the amount of drag, caused by friction and inertia when moving through the water.
One of the most common dinghy hulls in the world is the Laser hull. It was designed by Bruce Kirby in 1969 and unveiled at the New York boat show (1971). It was designed with speed and simplicity in mind. The Laser is 13 feet 10.5 inches long and a 12.5 foot water line and 76 square feet (7.1 m2) of sail.
Seamanship encompasses all aspects of taking a sailing vessel in and out of port, navigating it to its destination, and securing it at anchor or alongside a dock. Important aspects of seamanship include employing a common language aboard a sailing craft and the management of lines that control the sails and rigging.[62]
Further information: Glossary of nautical terms |
Nautical terms for elements of a vessel: starboard (right-hand side), port or larboard (left-hand side), forward or fore (frontward), aft or abaft (rearward), bow (forward part of the hull), stern (aft part of the hull), beam (the widest part). Spars, supporting sails, include masts, booms, yards, gaffs and poles. Moveable lines that control sails or other equipment are known collectively as a vessel's running rigging. Lines that raise sails are called halyards while those that strike them are called downhauls. Lines that adjust (trim) the sails are called sheets. These are often referred to using the name of the sail they control (such as main sheet or jib sheet). Guys are used to control the ends of other spars such as spinnaker poles. Lines used to tie a boat up when alongside are called docklines, docking cables or mooring warps. A rode is what attaches an anchored boat to its anchor.[63]
The following knots are regarded as integral to handling ropes and lines, while sailing:[64][65]
Lines and halyards are typically coiled neatly for stowage and reuse.[66]