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Sail-plan
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A sail-plan is a formal set of drawings, usually prepared by a naval architect. It shows the various combinations of sail proposed for a sailing ship.
The combinations shown in a sail-plan almost always include three configurations:
A light air sail plan. Over most of the Earth, most of the time, the wind force is Force 1 or less. Thus an effective sail plan should include a set of huge, lightweight sails that will keep the ship underway in light breezes.
A working sail plan. This is the set of sails that are changed rapidly in variable conditions. They are much stronger than the light air sails, but still lightweight. An economical sail in this set will include several sets of reefing ties, so the area of the sail can be reduced in a stronger wind.
A storm sail plan. This is the set of very small, very rugged sails flown in a gale, to keep the vessel under way and in control.
In all sail plans, the architect attempts to balance the force of the sails against the drag of the underwater keel in such a way that the vessel naturally points into the wind. In this way, if control is lost, the vessel will avoid broaching (turning edge-to-the wind), and being beaten by breaking waves. Broaching always causes uncomfortable motion, and in a storm, the breaking waves can destroy a lightly-built boat.
The architect also tries to balance the wind force on each sail plan against a range of loads and ballast. The calculation assures that the sail will not knock the vessel sideways with its mast in the water, a capsize and possible sinking.
TerminologyIn English, thanks to the British Admiralty, all sail-plans call a sail by the same name, no matter what their sail-plan. Once a sail is named, its lines have standard names according to their use. Once a sailor learns the standard names for the sails, he knows the terms for all the parts on any sail-plan.
A sail plan is made by combining just a few basic types of sails:
- A fore and aft sail is one that, when flat, runs fore and aft. These types of sails are the easiest to manage, because they often do not need to be relaid when the ship changes course.
- A gaff rigged sail is a fore-and-aft sail shaped like a truncated triangle the upper edge of which is made fast to a spar called a gaff. The top of the gaff rigged sail tends to twist away from the wind reducing its efficiency when close-hauled. However, due to the gaff on the top edge of the sail the center of effort is typically lower, somewhat reducing the angle of heel (leaning of the boat caused by wind force on the sails) compared to a similar sized Bermuda rigged sail.
- A square sail is set square to the mast from a yard, a spar running transversely in relation to the hull (athwartships). To furl and unfurl this sail, sailors would have to climb the rigging and walk out on "footropes" under the yard. It is not, as commonly thought, named after its approximate shape. Some cruising craft with fore-and-aft sails will carry a small square sail with top and bottom yards that are easily rigged and hauled up from the deck (not requiring climbing the mast); such a sail is used as the only sail when running downwind under storm conditions, as the vessel becomes much easier to handle than under its usual sails, even if they are severely reefed (shortened).
- A lateen sail is a triangle with one or two sides attached to a wooden pole. This is one of the lowest drag (the sailing term is windage) sails, and it is not easy to manage.
- A Bermuda or Marconi sail is a triangular sail with one point going straight up.
- A staysail ("stays'l") is a piece of cloth that has one or two sides attached to a stay, that is, one of the ropes or wires that helps hold the mast in place. A staysail was classically attached to the stay with wooden or steel hoops. Sailors would test the hoops by climbing on them.
- A jib is a staysail that flies in front of the foremost vertical mast.
- a bowsprit is a horizontal spar extending from the bow (front) of the boat. It is used to attach the forestay to the foremost mast.
Sails were classically made of hemp or cotton. They are now made from polyesters|PET film]]), sometimes reinforced with crystalline hydrocarbons. Some large, lightweight sails are made of polyamides.
Ropes are almost as important:
- Standing rigging does not change position. Usually it braces the masts.
- Running rigging is used to adjust sails and anchors.
- A line is a rope that has been put to use aboard a sailing vessel.
- A stay is a wire or rope that supports a mast. It is part of the standing rigging, usually located in the fore-aft plane of the vessel.
- A shroud is similar to a stay, but is located in the athwartship plane of the vessel. Thus, shrouds come down to the sides of the boat and are attached to chainplates.
- A vang is a rope used to pull something around or down.
- A sheet is a line used to adjust the position of a sail so that it catches the wind properly.
- A block is the seaman's name for a pulley-block. It may be fixed to some part of the vessel or spars, or even tied to the end of a line.
- The sheave is the wheel within a block, or a spar, over which a line is rove.
- A fiddle block has two or more sheaves in one block, each with its own axle, so the sheaves are aligned.
- A snatch-block can be closed around a line, to grab the line, rather than threading the end of the line through the block.
- A shackle is a piece of metal to attach two ropes, or a block to a rope, or a sail to a rope. Customarily, a shackle has a screw-in pin which often is so tight that a shackle-key must be used to unscrew it. A snap-shackle does not screw, and can be released by hand, but it is usually less strong or more expensive than a regular shackle.
- halyards are the lines on which one pulls to hoist something; e.g. the main-topgallant-staysail-halyard would be the line on which one pulls to hoist (unfurl) the main-topgallant-staysail.
- running lines are made fast (unmoving) by belaying them to (wrapping them around) a cleat or a belaying-pin located in a pin-rail.
Ropes were classically made of manila, cotton, hemp, or jute; papyrus (in ancient Egypt) and coir have also been seen. They are now made of stainless steel (301), galvanized steel, polyester (Dacron), polyamides (nylon), and sometimes crystallized hydrocarbons (Kevlar and Spectra).
The standard terminology assumes three masts, from front to back, the fore-mast, main-mast and mizzen-mast. On ships with fewer than three masts, the tallest is the main-mast. Ships with more masts number them. Some barks (see below) have had as many as twelve masts.
The heights of the sails on a square-rigged vessel are named roughly after the bravery of the man needed to work on each, except the skysail ("skys'l"). From bottom to top, the sails of each mast are named by the mast and position on the mast, e.g. for the mainmast, from lowest to highest: main course, main topsail, main topgallant ("t'gallant"), main royal, and main skysail. Since the early twentieth century, the topsails and topgallants are often split into a lower and an upper sail to allow them to be more easily handled.
On many warships, sails above the fighting top (a platform just above the lowest sail on which snipers were positioned) were mounted on separate masts ("topmasts" or "topgallant masts") held in wooden sockets called "tabernacles". These masts and their stays could be rigged or struck as the weather and tactical situation demanded.
In light breezes, the working square sails would be supplemented by studding sails ("stuns'l") out on the ends of the yardarms. These were called as a regular sail, with the addition of "studding". For example, the main top studding sail.
The staysails between the masts are named from the sail immediately below the highest attachment point of the stay holding up the staysail. Thus, the mizzen topgallant staysail can be found dangling from the stay leading from above the mizzen (third) mast's topgallant sail to some place (usually two sails down) on the second (main) mast.
The jibs, staysails between the first mast and the bowsprit, were named (in order of distance along the bowsprit) fore topmast staysail (or foretop stay), inner jib, outer jib and flying jib. All of the jib's stays meet the foremast just above the fore topgallant. Unusually, a fore royal staysail may also be set.
The stays below a bowsprit are martingales, and those above it bracing the bowsprit are bobstays. The martingales are often the strongest stays on a ship, and often constructed of chain. The pole hanging vertically down from the bowsprit is called the "dolphin striker".
The stays on a ship roughly form hoops of tension holding the masts up against the wind. Many ships have been "tuned" by tightening the rigging in one area, and loosening it in others. The tuning can create most of the stress on the stays in some ships. This was a common emergency procedure on sailing warships.
Almost every type of tall ship had a gaff-sail on the mizzenmast, and called it the spanker. This would sometimes be split into lower and upper spankers.
A ship would fly its ensign and anchor light off a drop line from the spanker's gaff.
Standard plans - Sloop: a Bermuda or gaff mainsail lifted by a single mast with a single jib bent onto the forestay, held taut with a backstay. The mainsail is usually managed with a spar on the underside called a "boom." One of the best-performing rigs per square foot of sail area and is fast for up-wind passages. In modern times by far the most popular for recreational boating because of its potential for high performance. On small boats, it can be a simple rig. On larger sloops, the large sails have high loads, and one must manage them with winches or multiple purchase block-and-tackles.
- Cutter: like a sloop with two jibs (a staysail and a yankee) in the foretriangle. Better than a sloop for light winds, it's also easier to manage. It has slightly less up-wind ability than a sloop because it has more windage.
- Yawl: like a sloop or catboat with a mizzen mast located aft (closer to the stern of the vessel) of the rudder post. The mizzen is relatively small, and is intended to help provide helm balance.
- Ketch: like a yawl, but the mizzenmast is often much larger, and is located forward of the rudder post. The purpose of the mizzen sail in a ketch rig, unlike the yawl rig, is to provide drive to the hull. A ketch rig allows for shorter sails than a sloop with the same sail area, resulting in a lower center of sail and less overturning momentum. The shorter masts therefore reduce the amount of ballast and stress on the rigging needed to keep the boat upright. Generally the rig is safer and less prone to broaching or capsize than a comparable sloop, and has more flexibility in sailplan when reducing sail under strong crosswind conditions – the mainsail can be brought down entirely (not requiring reefing) and the remaining rig will be both balanced on the helm and capable of driving the boat. The ketch is a classic small cargo boat.
- Catboat: a sailboat with a single mast and single sail, usually gaff-rigged. This is the easiest sail-plan to sail, and is used on the smallest and simplest boats. The catboat is a classic fishing boat. A popular movement among home-built boats uses this simple rig to make "folk-boats." One of the advantages of this type is that it can be rigged with no boom to hit one's head or knock one into the water. However, the gaff requires two halyards and often two topping lifts. The weight of the gaff spar high in the rigging can be undesirable. The gaff's fork (jaws) is held on by a rope threaded through beads called trucks (US) or parrel beads (UK). The gaff must slide down the mast, and therefore prevents any stays from bracing the mast. This usually makes the rig even heavier, requiring yet more ballast.
- Gunter: a rig designed for smaller boats where the mast is often taken down. It consists of a relatively short mast (usually slightly shorter than the boat so that it can be stowed inside) and a long gaff (often only slightly shorter than the mast). However, rather than the usual trapezoidal shape of a gaff sail, it is essentially triangular, like a Bermuda rig. This allows the gaff, when hoisted, to pivot upwards until it is vertical, effectively forming an extension to the mast. Thus a decent-sized sailing rig can be added to the boat while still allowing all the equipment to be stowed completely inside it. The popular Mirror class of dinghy is gunter rigged for this reason.
- Schooner: a fore-and-aft rig having at least two masts, with a foremast that is usually smaller than the other masts. Schooners have traditionally been gaff-rigged and in small craft are generally two-masted, however many have been built with Marconi rigs (and even junk rigs) rather than gaffs and in the golden age of sail, vessels were built with as many as seven masts. One of the easiest types to sail, but performs poorly to windward without gaff topsails. The extra sails and ease of the gaff sails make the rig easier to operate, though not necessarily faster, than a sloop on all points of sail other than up-wind. Schooners were more popular than sloops prior to the upsurge in recreational boating. The better performance of the sloop upwind was outweighed for most sailors by the better performance of the schooner at all other, more comfortable, points of sail. Advances in design and equipment over the last hundred years have diminished the advantages of the schooner rig. Many schooners sailing today are either reproductions or replicas of famous schooners of old.
- Brig: two masts, both square-rigged with a spanker on the mainmast.
- Brigantine: two masts, square-rigged on the foremast and fore-and-aft rigged on the mainmast.
- Barquentine: is a three masted vessel, square rigged on the foremast and fore-an-aft rigged on the main and mizzen masts. Some sailors who have sailed on them say it is a poor-handling compromise between a barque and a ship, though having more speed than a barque or schooner.
- Barque: three masts or more, square rigged on all except the aftmost mast. Usually three or four masted but five masted barques have been built. Lower-speed, especially downwind, but requiring fewer sailors than a ship. This is a classic slow-cargo ship.
- Fully rigged Ship: three or more masts, square rigged on all, with stay-sails between. The classic ship rig originally had exactly three masts, but four and five masted ships were also built. The classic sailing warship — the ship of the line — was fully rigged in this way, because of high performance on all points of wind. They were larger than brigs and brigantines, and faster than barques or barquentines, but required more sailors.
- Bragana or felucca: a classic in the Mediterranean or Indian Ocean. Three lateen sails in a row.
- Polacre: a three master with a narrow hull; carrying a square-rigged foremast, followed by two lateen sails. The same vessel, if she substituted her square-rigged mast with another lateen rigged one, would be called a xebec.
- junk: the standard Chinese design: Elliptical sails made flat with bamboo inserts (battens), permitting them to sail well on any point of sail. Easy to sail, and reasonably fast. The nature of the rig places no extreme loads anywhere on the sail or rigging, thus can be built using light-weight, less expensive materials. Some of the largest sailing ships ever constructed were junks for the Chinese treasure fleets. Junks also customarily had internal water-tight rooms, kept so by not having doors between them. Usually they were constructed of teak or mahogany.
Sail-Plan MeasurementsEvery sail-plan has maximum dimensions. These maxima are for the largest sail possible and they are defined by a letter abbreviation.
- J The base of the foretriangle measured along the deck from the forestay pin to the front of the mast.
- I The height measured along the front of mast from the jib halyard to the deck.
- E The foot length of the mainsail along the boom.
- P The luff length of the mainsail measured along the aft of the mast from the top of the boom to the highest point that the mainsail can be hoisted at the top of the mast.
- Ey The length of a second boom (For a Ketch or Yawl).
- Py The height of the second mast from the boom to the top of the mast.
See also
External reference
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