Archive: Sail Plan

Sail plan
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.

Terminology
In 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 ropes 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 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.
• 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's often easy to manage.
• A Bermuda or Marconi sail is a triangular sail with one point going straight up.
• A staysail 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 (Dacron and PET film), sometimes reinforced with crystalline hydrocarbons (Kevlar and Spectra™). Some large, lightweight sails are made of polyamides (Nylon).
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.
• a stay is a rope that doesn't move, 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 rope used to adjust the position of a sail so that it catches the wind properly.
• a block is the nautical name for a pulley. It may be fixed to some part of the vessel or spars, or even tied to the end of a rope.
  • The sheave is the wheel.
  • A fiddle block has two or more sheaves in one block.
  • 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 doesn't screw, and can be released by hand, but it's usually less strong or more expensive than a regular shackle.
• halyards are the ropes on which one pulls to hoist something. E.g. the main-topgallant-halyard would be the rope on which one pulls to hoist (unfurl) the main-topgallant-sail.
• 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. 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. 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 (pronounced "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 (pronounced "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, the staysails between the first mast and the bowsprit, were named (in order of distance along the bowsprit) fore topmast staysail, 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. The martingale has similarity with the martingale on a horse's bridle, which prevents the horse's head from being raised further than a desired point, 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 taught 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.

Characteristics

The mainsail of a sloop may be Bermuda or gaff rigged. The luff of the mainsail is attached to the mast by a track, hoops or other means, and the mainsail foot is managed by a boom.

A sloop traditionally carries a single jib, bent onto the forestay. It is often compared to the similar cutter which traditionally carries multiple jibs. The distinction between sloop and cutter has become somewhat lost in recent years, and the terms are used interchangeably by some production builders and marketing types.

The sloop rig may be masthead, meaning that the forestay (on which the jib is carried) is affixed to the masthead, or fractional if the forestay is affixed somewhat farther down the mast.​

Examples

The vast majority of small to medium sized recreational boats are sloop rigged.

The rig is also popular among extreme high-performance race boats.
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Performance

The sloop rig is generally viewed as one of the best-performing rigs for a given sail area, and can be designed for excellent windward ability.​

Handling

For boats under ten metres / 30 feet, the sloop rig can be very simple and easily managed. In one- or two-person dinghies, few control lines are needed and their loads are light, making the sloop an ideal training rig.

In larger sizes, the loading on the sloop's two sails becomes very high. Multiple block-and-tackle systems become necessary to manage the sheets, along with large (and sometimes powered or multi-speed) winches.​

• cutter, Like a sloop with two jibs (a staysail and a yankee) in the foretriangle. Better than a sloop for light winds. It's easier to manage, too. But, it has (very) slightly less up-wind ability than a sloop because it has more windage.

Characteristics

Cutters may carry a Bermuda or gaff rigged mainsail. Its foot is managed by a boom, and its luff is secured to the mast.

The traditional cutter is distinguished from the sloop by its multiple headsails, as compared to the single jib carried by the sloop. However, it has become common in recent years for boats to be marketed as "sloops" or "cutters" based on marketing preference, rather than the actual rig, and the distinction between the two is not always respected.
​

• yawl, is 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.

Characteristics

The yawl's mizzen mast is stepped aft of the rudder post, distinguishing it from the ketch whose larger mizzen is carried forward of the rudder.

A yawl's mizzen is generally quite small, and does not contribute significantly to propulsion. The mizzen serves to provide the skipper with better control over the helm balance, allowing him/her to adjust the helm balance as wind direction and boat speed change.​

• ketch, is 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 also 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 moment. 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 adverse conditions. The ketch is a classic small cargo boat.

Characteristics

A ketch rig is a two-masted fore-and-aft rig, where the mainmast is located forward of a smaller mizzen mast. Each mast carries either a gaff or Bermudan sail, and one or more jibs may be carried ahead of the mainmast. If the mizzen accounts for a substantial part of the sail area, additional staysails are occasionally carried on the mizzen mast.

ue to the added drag of the extra mast it is advisable to have the mizzen as 20% or more of the total ‘design’ sail area, (the fore triangle + main + mizzen ). A good separation between the two masts allows the carrying of a large light air mizzen staysail which is a real boon with this rig. A smaller staysail can be flown in the triangle between the leech of the main and the mizzen mast, this is called a mizzen mule, the clew of the mule is sheeted to the mizzen mast top. On larger boats the fore-triangle with often be a cutter arrangement and we often see this rig with a bowsprit.

The ketch is distinguished from its close cousin the yawl by the location of its mizzen mast. Where a yawl carries a small mizzen mast aft of the rudder post for helm balance, the ketch carries a larger mizzen for both balance and propulsion, with the mizzen mast stepped ahead of the rudder.

A variant known as a cat-ketch moves one mast close to the bow, catboat style, with the second mast usually just aft of amidships. In this setup, both masts are usually free-standing and carry sails of about the same size.​

• 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 parrell 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.

Characteristics

The catboat may carry its mainsail in virtually any fashion- it might be gaff rigged, or Bermudan, or lateen, or virtually any other fore-and-aft setup. It is distinguished primarily by the fact that its mast is stepped in the bow.

The traditional catboat, in the purest sense, has a gaff-rigged sail, usually with a gaff nearly as long as the boom; however, the term is generally used for any vessel whose single mast is stepped in the forepeak.​

Examples

The Nonsuch line of cruisers is perhaps the best known catboat among cruising sailboats. Built in 22', 26', 30', 33' and 36' versions by Hinterhoeller Yachts in St. Catharines, Ontario, the Nonsuch carried a single triangular sail on an unstayed mast with wishbone boom.

Catboat rigs were used on small fishing boats long before accurate records of their design and numbers were kept, and continue to be a popular choice for smaller craft.
​

• 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 bark and a ship, though having more speed than a bark 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.

• ship a series of square-rigged masts, with stay-sails between. Ships originally had exactly three masts but four and five masted ships were also built. Faster, but requiring more sailors than a barque. The ship was the classic sailing warship because it had the highest performance on all points of wind.

• bragana or felucca: A classic in the Mediterranean or Indian Ocean: three lateen sails in a row.

• xebec, a three master with square-rigged first mast, and two lateen sails following.

• 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.

From Sail plan - Wikipedia http://en.wikipedia.org/wiki/Sail-plan#Terminology
Text is available under the terms of the GNU Free Documentation License.

Note: this is an archived page from the Boat Design Wiki project which was active from 2007 through 2010 and archived in 2017.