Cmmdre
07-13-2013, 09:06
The point of sail describes a sailing boat's course in relation to the wind direction.
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No sailboat can sail directly into the wind (known as being "in irons"), and for a given boat there is a minimum angle that it can sail relative to the wind; attempting to sail closer than that leads to the sails luffing and the boat will slow down and stop. This "no-go zone" (shown shaded in accompanying figure) is about 45° either side of the true wind for a modern sloop.
There are 5 main points of sail. In order from the edge of the no-go zone (or "irons") to directly downwind they are:
close haul (the minimum angle to the wind that the boat and its rig can manage - typically about 45° )
close reach (between close hauled and a beam reach)
beam reach (approximately 90° to the wind)
broad reach (between a beam reach and running)
running (close to directly downwind)
The sail trim on a boat is relative to the point of sail one is on: on a beam reach sails are mostly let out, on a run sails are all the way out, and close hauled sails are pulled in very tightly. Two main skills of sailing are trimming the sails correctly for the direction and strength of the wind, and maintaining a course relative to the wind that suits the sails once trimmed.
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Close Hauled or "Beating"
Using a series of close-hauled legs to beat a course upwind.
A boat can be 'worked to windward', to arrive at an upwind destination, by sailing close-hauled with the wind coming from one side, then tacking (turning the boat through the eye of the wind) and sailing with the wind coming from the other side. By this method of zig-zagging into the wind, known as beating, it is possible to reach any upwind destination.[9] A yacht beating to a mark directly upwind one mile away will cover a distance through the water of at least 1.4 miles, if it can tack through an angle of 90 degrees including leeway. An old adage describes beating as sailing for twice the distance at half the speed and three times the discomfort.[13]
An estimate of the correct tacking distance can be obtained (and thereby the time taken to travel it at various boat speeds) by using Pythagoras' theorem with equal tacks (assume a value of 1). This also assumes a tacking angle of 90°. The straight line distance is the hypotenuse value of √2
When beating to windward one tack may be more favorable than the other - more in the desired direction. The best strategy is to stay on the favorable tack as much as possible. If the wind shifts in the sailor's favor, called a lift, so much the better, then this tack is even more favorable. But if it shifts against the sailor's, called a header, then the opposite tack may become the more favorable course. So when the destination is directly into the wind the best strategy is given by the racing adage "tack on a header." This is true because a header on one tack is a lift on the other.
How closely a boat can sail into the wind depends on the boat's design, sail shape and trim, the sea state, and the wind speed.
Typical minimum pointing angles to the true wind are as follows. Actual course over the ground will be worse due to leeway.
about 35° for modern racing yachts which have been optimized for upwind performance (like America's Cup yachts)
about 40 to 45° for modern cruiser-racer yachts (fast cruising yachts)
about 50 to 60° for cruisers and workboats with inefficient keels, inefficient hull shapes, or low draught, when compared to craft designed for sailing performance, and for boats carrying two or more masts (since the forward sails adversely affect the windward ability of sails further aft when sailing upwind)
close to 90° for square riggers and similar vessels due to the sail shape which is very ineffective when sailing upwind
Sailing close-hauled under a large amount of sail, and heeling a great deal, can induce weather helm, or a tendency for the boat to turn into the wind. This requires pulling the tiller to windward (i.e. 'to weather'), or turning the wheel leeward, in order to counteract the effect and maintain the required course. The lee side of the hull is more under water than the weather side and the resulting shape of the submerged parts of the hull usually creates a force that pushes the bow to weather. Driving both the asymmetric heeling hull form and the angled rudder through the water produces drag that slows the boat down. If weather helm builds further, it can limit the ability of the helmsman to steer the boat, which can be turned towards but not effectively away from the wind. At more extreme angles of heel, the boat will spontaneously 'round up' into the wind during gusts, i.e. it will turn into the wind regardless of any corrective action taken on the helm.
Any action that reduces the angle of heel of a boat that is reaching or beating to windward will help reduce excessive weather helm. Racing sailors use their body weight to bring the boat to a more upright position, but are not allowed to use "movable ballast" during a race. [14] Reducing or reefing the total sail area will have the same effect and many boats will sail faster with less sail in a stiff breeze due to the reduction in underwater drag. Easing the sheets on aft-most sails, such as the mainsail in a sloop or cutter can have an immediate effect, especially to help with manoeuvering. Moving or increasing sail area forward can also help, for example by raising the jib (and maybe lowering the staysail) on a cutter.
Reaching
When the boat is traveling approximately perpendicular to the wind, this is called reaching. A beam reach is with the wind at right angles to the boat, a close reach is anywhere between beating and a beam reach, and a broad reach is between a beam reach and running.
For most modern sailboats, that is boats with fore-and-aft sails, reaching is the fastest way to travel. The direction of the wind is ideal when reaching because it can maximize the lift generated on the sails in the forward direction of the boat, giving the best boat speed. Also when reaching, the boat can be steered exactly in the direction that is most desirable, and the sails can be trimmed for that direction.
Reaching may, however, put the boat on a course parallel with the crests of the waves. When the waves are steep, it may be necessary to sail closer to the wind to avoid waves directly on the beam.
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Running
Sailing the boat within roughly 30 degrees either side of dead downwind is called a run. This can be the most comfortable point of sail, but requires constant attention. Loss of attention by the helmsman can lead to an accidental jibe, causing injury to the boat or crew. All on deck must be aware of, and if possible avoid, the potential arc of the boom, mainsheet and other gear in case an accidental jibe occurs during a run. A preventer can be rigged to reduce danger and damage from accidental jibes.
This is generally the most unstable point of sail, but the easiest for a novice to grasp conceptually, making it a common downfall for beginners. In stronger winds, rolling increases as there is less rolling resistance provided by the sails, as they are eased out. Also, having the sails and boom(s) perpendicular to the boat throws weight and some wind force to that side, making the boat harder to balance. In smaller boats, death rolls can build up and lead to capsize.
Also on a run an inexperienced or inattentive sailor can easily misjudge the real wind strength since the boat speed subtracts directly from the true wind speed and makes the apparent wind less. In addition sea conditions can also falsely seem milder than they are as the waves ahead are being viewed from behind making white caps less apparent. When changing course from this point of sail to a reach or a beat, a sailboat that seemed under control can instantly become over-canvassed and in danger. Any boat over-canvassed on a run can round up, heel excessively and stop suddenly in the water. This is called broaching and it can lead to capsize, possible crew injury and loss of crew into the water.
Options for maneuvering are also reduced. On other points of sail, it is easy to stop or slow the boat by heading into the wind; there may be no such easy way out when running, especially in close quarters or when a spinnaker, whisker pole or preventer are set.
5779
See more here.
http://en.wikipedia.org/wiki/Sailing
http://en.wikipedia.org/wiki/Points_of_sail
Or...
http://www.sailsofglory.org/showthread.php?1095-HOLDING-THE-WEATHER&highlight=holding+weather
http://www.sailsofglory.org/showthread.php?1131-GLOSSARY-OF-NAUTICAL-TERMS&highlight=glossary+nautical+terms
http://www.sailsofglory.org/showthread.php?829-Seamanship-ion-the-Age-of-Sail&highlight=Seamanship+Age+Sail
Further information...
http://web.mit.edu/2.972/www/reports/sail_boat/sail_boat.html
http://www.physics.unsw.edu.au/~jw/sailing.html
5776
No sailboat can sail directly into the wind (known as being "in irons"), and for a given boat there is a minimum angle that it can sail relative to the wind; attempting to sail closer than that leads to the sails luffing and the boat will slow down and stop. This "no-go zone" (shown shaded in accompanying figure) is about 45° either side of the true wind for a modern sloop.
There are 5 main points of sail. In order from the edge of the no-go zone (or "irons") to directly downwind they are:
close haul (the minimum angle to the wind that the boat and its rig can manage - typically about 45° )
close reach (between close hauled and a beam reach)
beam reach (approximately 90° to the wind)
broad reach (between a beam reach and running)
running (close to directly downwind)
The sail trim on a boat is relative to the point of sail one is on: on a beam reach sails are mostly let out, on a run sails are all the way out, and close hauled sails are pulled in very tightly. Two main skills of sailing are trimming the sails correctly for the direction and strength of the wind, and maintaining a course relative to the wind that suits the sails once trimmed.
5777
Close Hauled or "Beating"
Using a series of close-hauled legs to beat a course upwind.
A boat can be 'worked to windward', to arrive at an upwind destination, by sailing close-hauled with the wind coming from one side, then tacking (turning the boat through the eye of the wind) and sailing with the wind coming from the other side. By this method of zig-zagging into the wind, known as beating, it is possible to reach any upwind destination.[9] A yacht beating to a mark directly upwind one mile away will cover a distance through the water of at least 1.4 miles, if it can tack through an angle of 90 degrees including leeway. An old adage describes beating as sailing for twice the distance at half the speed and three times the discomfort.[13]
An estimate of the correct tacking distance can be obtained (and thereby the time taken to travel it at various boat speeds) by using Pythagoras' theorem with equal tacks (assume a value of 1). This also assumes a tacking angle of 90°. The straight line distance is the hypotenuse value of √2
When beating to windward one tack may be more favorable than the other - more in the desired direction. The best strategy is to stay on the favorable tack as much as possible. If the wind shifts in the sailor's favor, called a lift, so much the better, then this tack is even more favorable. But if it shifts against the sailor's, called a header, then the opposite tack may become the more favorable course. So when the destination is directly into the wind the best strategy is given by the racing adage "tack on a header." This is true because a header on one tack is a lift on the other.
How closely a boat can sail into the wind depends on the boat's design, sail shape and trim, the sea state, and the wind speed.
Typical minimum pointing angles to the true wind are as follows. Actual course over the ground will be worse due to leeway.
about 35° for modern racing yachts which have been optimized for upwind performance (like America's Cup yachts)
about 40 to 45° for modern cruiser-racer yachts (fast cruising yachts)
about 50 to 60° for cruisers and workboats with inefficient keels, inefficient hull shapes, or low draught, when compared to craft designed for sailing performance, and for boats carrying two or more masts (since the forward sails adversely affect the windward ability of sails further aft when sailing upwind)
close to 90° for square riggers and similar vessels due to the sail shape which is very ineffective when sailing upwind
Sailing close-hauled under a large amount of sail, and heeling a great deal, can induce weather helm, or a tendency for the boat to turn into the wind. This requires pulling the tiller to windward (i.e. 'to weather'), or turning the wheel leeward, in order to counteract the effect and maintain the required course. The lee side of the hull is more under water than the weather side and the resulting shape of the submerged parts of the hull usually creates a force that pushes the bow to weather. Driving both the asymmetric heeling hull form and the angled rudder through the water produces drag that slows the boat down. If weather helm builds further, it can limit the ability of the helmsman to steer the boat, which can be turned towards but not effectively away from the wind. At more extreme angles of heel, the boat will spontaneously 'round up' into the wind during gusts, i.e. it will turn into the wind regardless of any corrective action taken on the helm.
Any action that reduces the angle of heel of a boat that is reaching or beating to windward will help reduce excessive weather helm. Racing sailors use their body weight to bring the boat to a more upright position, but are not allowed to use "movable ballast" during a race. [14] Reducing or reefing the total sail area will have the same effect and many boats will sail faster with less sail in a stiff breeze due to the reduction in underwater drag. Easing the sheets on aft-most sails, such as the mainsail in a sloop or cutter can have an immediate effect, especially to help with manoeuvering. Moving or increasing sail area forward can also help, for example by raising the jib (and maybe lowering the staysail) on a cutter.
Reaching
When the boat is traveling approximately perpendicular to the wind, this is called reaching. A beam reach is with the wind at right angles to the boat, a close reach is anywhere between beating and a beam reach, and a broad reach is between a beam reach and running.
For most modern sailboats, that is boats with fore-and-aft sails, reaching is the fastest way to travel. The direction of the wind is ideal when reaching because it can maximize the lift generated on the sails in the forward direction of the boat, giving the best boat speed. Also when reaching, the boat can be steered exactly in the direction that is most desirable, and the sails can be trimmed for that direction.
Reaching may, however, put the boat on a course parallel with the crests of the waves. When the waves are steep, it may be necessary to sail closer to the wind to avoid waves directly on the beam.
5778
Running
Sailing the boat within roughly 30 degrees either side of dead downwind is called a run. This can be the most comfortable point of sail, but requires constant attention. Loss of attention by the helmsman can lead to an accidental jibe, causing injury to the boat or crew. All on deck must be aware of, and if possible avoid, the potential arc of the boom, mainsheet and other gear in case an accidental jibe occurs during a run. A preventer can be rigged to reduce danger and damage from accidental jibes.
This is generally the most unstable point of sail, but the easiest for a novice to grasp conceptually, making it a common downfall for beginners. In stronger winds, rolling increases as there is less rolling resistance provided by the sails, as they are eased out. Also, having the sails and boom(s) perpendicular to the boat throws weight and some wind force to that side, making the boat harder to balance. In smaller boats, death rolls can build up and lead to capsize.
Also on a run an inexperienced or inattentive sailor can easily misjudge the real wind strength since the boat speed subtracts directly from the true wind speed and makes the apparent wind less. In addition sea conditions can also falsely seem milder than they are as the waves ahead are being viewed from behind making white caps less apparent. When changing course from this point of sail to a reach or a beat, a sailboat that seemed under control can instantly become over-canvassed and in danger. Any boat over-canvassed on a run can round up, heel excessively and stop suddenly in the water. This is called broaching and it can lead to capsize, possible crew injury and loss of crew into the water.
Options for maneuvering are also reduced. On other points of sail, it is easy to stop or slow the boat by heading into the wind; there may be no such easy way out when running, especially in close quarters or when a spinnaker, whisker pole or preventer are set.
5779
See more here.
http://en.wikipedia.org/wiki/Sailing
http://en.wikipedia.org/wiki/Points_of_sail
Or...
http://www.sailsofglory.org/showthread.php?1095-HOLDING-THE-WEATHER&highlight=holding+weather
http://www.sailsofglory.org/showthread.php?1131-GLOSSARY-OF-NAUTICAL-TERMS&highlight=glossary+nautical+terms
http://www.sailsofglory.org/showthread.php?829-Seamanship-ion-the-Age-of-Sail&highlight=Seamanship+Age+Sail
Further information...
http://web.mit.edu/2.972/www/reports/sail_boat/sail_boat.html
http://www.physics.unsw.edu.au/~jw/sailing.html