Sail plan


A sail plan is a description of the specific ways that a sailing craft is rigged, as [|discussed below]. Also, the term “sail plan” is a graphic depiction of the arrangement of the sails for a given sailing craft.

Overview

A well-designed sail plan should be balanced, requiring only light forces on the helm to keep the sailing craft on course. The fore-and-aft center of effort on a sail plan is usually slightly behind the center of resistance of the hull, so that the sailing craft will tend to turn into the wind if the helm is unattended. The height of the sail plan's center of effort above the surface is limited by the sailing craft's ability to avoid capsize, which is a function of its hull shape, ballast, or hull spacing.

Types of rig

Each form of rig requires its own type of sails. Among them are:
The standard terminology assumes three masts, from front to back, the foremast, mainmast and mizzenmast. On ships with fewer than three masts, the tallest is the mainmast. Ships with more masts number them.
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, main royal, main skysail, and main moonraker. Since the early nineteenth century, the topsails and topgallants are often split into a lower and an upper sail to allow them to be more easily handled. This makes the mast appear to have more "sails" than it officially has.
On many ships, sails above the top were mounted on separate masts held in wooden sockets called "trestletrees". These masts and their stays could be rigged or struck as the weather conditions required, or for maintenance and repair.
In light breezes, the working square sails would be supplemented by studding sails 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.
Between the main mast and mizzen as well as between main mast and foremast, the staysails between the masts are named from the sail immediately below the highest attachment point of the stay holding up that staysail. Thus, the mizzen topgallant staysail can be found dangling from the stay leading from above the mizzen mast's topgallant sail to at least one and usually two sails down from that on the main mast.
The jibs are named fore topmast staysail, inner jib, outer jib and flying jib. Many of the jibs' stays meet the foremast just above the fore topgallant. A fore royal staysail may also be set.

Types of sailing vessels

Sailing vessels may be distinguished by:

Types of sails

Quadrilateral sails

Triangular sails

Trivia

All of these sails may have a boom along the bottom, or they may have none. A boom-footed sail gives better control of the sail shape and thus makes the sail more efficient, especially upwind. One of the advantages of boomless sails is that there is no boom to hit one's head or knock one into the water. Boats without booms are also lighter and cheaper to make.
Some gaff and some junk rigs get in the way of shroud lines strung between the mast and hull. If the mast cannot be held up by shrouds, it must stand up by itself, which makes it heavier, especially on a large boat.
A gunter rig is often used for smaller boats where the mast is frequently taken down; the mast is made short enough to be stored flat inside the boat. The popular Mirror class of racing dinghy is gunter-rigged for this reason.
Lug, lateen and settee sails have an efficient tack and an inefficient tack, in which the sail presses against the mast, spoiling its aerodynamics. Some swing their yards around the mast to make both tacks efficient, but this is difficult with larger sails.
Crab-claws are easily to construct, as they work well when cut from a single flat sheet. On a small boat like the Sunfish, their rigging can also be limited to one sheet and one halyard.
Junk rigs, like crab-claws, place no extreme loads anywhere on the sail or rigging, so they can be built using light-weight, weaker, less-expensive materials. The subdivided sails make them easy for a small crew to handle, and they are easy to reef. Junks also customarily have internal water-tight bulkheads, as do modern ships.

[Aspect ratio]

The sails above vary in shape from square to triangular. A triangular sail has half the surface area of a squarish sail of the same height. For the sails to have the same surface area, the triangular sail must be twice as tall.
There are several disadvantages to a tall rig. Firstly, it makes the boat less stable. If the sails are tall, the wind tends to push the boat over. A boat is also more tippy if it has a taller mast or heavy spars high up. An outrigger, ballast, and/or a long keel is needed to keep the boat upright. Secondly, a taller rig makes it harder to hold the mast onto the boat. Generally, taller rigs are more highly stressed structures than shorter rigs. This makes them more expensive and more fragile for a given strength of material. Stronger, cheaper modern materials are one reason why shorter, squarer rigs are becoming rare.
Why, then, use a tall triangular sail? Because it is more aerodynamic than a squarish one. Downwind, a sail acts like a windsock; the wind just hits and bounces, pushing the boat downwind. But at right angles to the wind, the sail catches the wind and redirects it, letting it sail faster than the wind. Pushing the wind around to a different direction pushes the sailboat off in the opposite direction. A sailboat can't sail directly upwind, but by redirecting the wind it can sail nearly upwind. It can then tack in a zigzag to move directly upwind.
A tall, thin sail redirects the wind more smoothly, so it can sail more nearly upwind than a wide sail. Sailing a race in a circle, everyone has to go upwind. So other things being equal, the most weatherly boat will win. This is why almost all racing boats have tall, thin sails. They also have deep, heavy keels, or are multihulls, so that they don't tip over, and strong standing rigging, so their masts don't blow off.
Boats with shorter, wider sails have lighter, shallower hulls. They may wait for a favorable wind to avoid sailing upwind. They may go faster than a high-aspect-ratio sailboat when not going upwind; for instance, crab-claws sail extremely well on a beam reach.
Distinctions in nomenclature
European, and especially English, watercraft terminology draws a strong distinction between square-rigged vessels and fore-and-aft rigged ones. It is important to note that any other sail, even if it is geometrically square, is not a square sail in the technical sense used in European sail terminology. It is merely a quadrilateral fore-and-aft sail. Vessels are named by the number of square-rigged masts that they have. This is because square-rigged vessels used to be the fastest rig, and more masts were faster.
Junk rigs essentially have the stack of sails, but without all the gaps between them. Where the yards controlled the towers of square sails, the battens controlled the junk sail. In East Asia, the largest and the smallest boats traditionally use junk sails, and vessels are not named by sail type, but by region, function, and other characteristics.
Likewise, in the Pacific both large and small sailing vessels traditionally use what are generally called crabclaw sails, although they are of many different types. Other sails are also traditionally used.
In the Middle East, on the east coast of Africa, and as far east as India, lateens and settees were in common use. Ships were named more with regard to purpose than number of masts or type of sail. For instance, feluccas and sambuks were mostly used for fishing and ferrying, dhows are heavy cargo vessels. Xebecs, which also had oars, were used by corsairs to outpace merchant vessels, which were also often xebecs.
Attempts to blend nomenclature, as in the junk diagram to the left above, occur. A ship can be rigged with one of its sails as a junk sail and another as a Bermuda rig without being considered a junk vessel.

Catboat (one mast, one sail)

A catboat is a sailboat with a single mast and single sail; for examples of the variety of catboats, see the section above. 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 for home-built boats uses this simple rig to make "folk-boats".
The term "catboat" is usually qualified by the type of sail, for example, "a gaff catboat".

Proa

A proa has one sail, and is thus a catboat, though it is rarely called a catboat. Both ends are alike, and the boat is sailed in either direction, but it has a fixed leeward side and a windward side. The boat is shunted from beam reach to beam reach to change direction, with the wind over the side, a low-force procedure. The bottom corner of the crabclaw sail is moved to the other end, which becomes the bow as the boat sets off back the way it came. The mast usually hinges, adjusting its rake. The proa is a low-stress rig, which can be built with simple tools and low-tech materials, but it is extremely fast. On a beam reach, it may be the fastest simple rig.
In a traditional Pacific proa, the outrigger lies on the windward side of the main hull, with its weight helping keep the proa upright. The ama is very thin, to punch through waves, smoothing the ride. The first Europeans, building proas from travelers' reports, built Atlantic proas, with the outrigger on the leeward side, with its buoyancy keeping the proa upright.
"To be clear, we can blame Richard C. Newick for the debate", "since it was he who came up with the Atlantic proa in the first place, with his groundbreaking Cheers - the “giant killer” that came in third in the 1968 OSTAR. Unlike all proas until Cheers, Newick placed the ama to lee and the rig to windward, concentrating all the ballast to windward and thus multiplying the righting moment."

Sloop (one mast, two sails)

A Bermuda or gaff mainsail lifted by a single mast with a single jib attached to a bowsprit, bent onto the forestay, held taut with a backstay. The mainsail is usually managed with a spar on the underside called a "boom".
A Bermuda-rigged sloop is one of the best racing rigs per square foot of sail area as is it very weatherly, making it faster on upwind passages. This rig is 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-tackle devices.

Cutter (one mast, two or more foresails)

A small single-masted ship with three or more sails. A common rig is a gaff-rigged mainsail, multiple headsails, and, often, a gaff- or square-rigged topsail above. Sometimes cutters also had an additional square-rigged mainsail when traveling downwind. The mast was normally set amidships, and two or more headsails were set from the mast to the running bowsprit. Considered better than a sloop for light winds; it is also easier to manage, as the sail area is more subdivided.

Multi-masted vessels

Schooner

A fore-and-aft rig having at least two masts, the foremast normally being shorter than the others. The rig is rarely found on a hull of less than 50 feet LOA, and small schooners are generally two-masted. In the two decades around 1900, larger multi-masted schooners were built in New England and on the Great Lakes with four, five, six, or even, seven masts. Schooners were traditionally gaff-rigged, and some schooners sailing today are either reproductions of famous schooners of old, but modern vessels tend to be Bermuda rigged. While a sloop rig is simpler and cheaper, the schooner rig may be chosen on a larger boat so as to reduce the overall mast height and to keep each sail to a more manageable size, giving a mainsail that is easier to handle and to reef. An issue when planning a two-masted schooner's rig is how to fill the space between the masts: for instance, one may adopt a gaff sail on the foremast, or a main staysail, often with a fisherman topsail to fill the gap at the top in light airs.

Topsail schooner

A topsail schooner also has a square topsail on the foremast, to which may be added a topgallant and other square sails, but not a fore course, as that would make the vessel a brigantine. A lower yard is still needed to carry the sheets of the square topsail. The fore and aft sails are as for any other schooner. The square sails improve downwind performance.

Lugger

A lugger is usually a two or three masted vessel, setting lug sails on each mast. A jib or staysail may be set on some luggers. More rarely, lug topsails are used by some luggers - notably the chasse-marée. A lug sail is an asymmetric quadrilateral sail that fastens to a yard along the head of the sail. The yard is held to the mast either by a parrel or by a traveller. A dipping lug sail is fastened at the tack some distance in front of the mast. A standing lug's tack is fastened near the foot of the mast. The halyard for a dipping lug is usually made fast to the weather gunwale, thereby allowing the mast to be unstayed. A common arrangement is to have a dipping lug foresail and a standing lug mizzen. This arrangement is found on many traditional British fishing vessels, such as the fifie - but there are examples of dipping lugs on two masts or standing lugs on all of 2 or 3 masts.
A standing lug may be used with or without a boom; most working craft were boomless to allow more working space. The dipping lug never uses a boom. A dipping lug has to be moved to the leeward side of the mast when going about, so that the sail can take a good aerodynamic shape on the new tack. There are several methods of doing this - one of which is to simply lower the sail, manhandle the yard and sail to the other side of the mast and re-hoist. All the various methods are time and labour consuming. A standing lug can be left unaltered when tacking as it still sets reasonably well with the sail pressed against the mast. Some users would still dip the yard of a standing lug. Conversely many fishermen would always hoist a standing lug on the same side of the mast regardless of which tack they expected to be sailing on.
Sailing performance with a standing lug relies on the right amount of luff tension. An essential component of this rig is the tack tackle, a purchase with which luff tension is adjusted for various points of sail.
The balanced lug has a boom that projects in front of the mast roughly the same distance as the yard. This is generally used in dinghies. The sail is left on the same side of the mast regardless of the wind direction. A downhaul is set up from the boom to a point close to the heel of the mast and its adjustment is critical to getting this sort of sail to set correctly.

Two-masted vessels

Ketch

A small ship with two masts, both fore-and-aft rigged, with the mizzen located well forward of the rudder post and of only slightly smaller size than the mainmast. If square-rigged on her mainmast above the course, it is called a "square topsail ketch". Historically the mainmast was square-rigged instead of fore-and-aft, but in modern usage only the latter is called a ketch. The purpose of the mizzen sail in a ketch rig, unlike the mizzen on a 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 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 sail plan when reducing sail under strong crosswind conditions—the mainsail can be brought down entirely 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.

Yawl

A small ship, fore-and-aft rigged on its two masts, with its mainmast much taller than its mizzen and with or without headsails. The mizzen mast is located aft of the rudderpost, sometimes directly on the transom, and is intended to help provide helm balance.

Bilander

The bilander is a two-masted vessel, the foremast carrying square rigs on all of its yards and its taller mainmast having a long lateen mainsail yard with corresponding trapezoidal sail and rig inclined at about 45° with square rigs on the yards above that, the lowermost secured at the corners by a crossjack. The design was popular in the Mediterranean Sea as well as around New England in the first half of the 18th century but was soon surpassed by better designs. It is considered the forerunner of the brig.

Brig

In American parlance, the brig encompasses three classes of ship: the full-rigged brig, the hermaphrodite brig, and the brigantine. All American brigs are defined by having exactly two masts that are entirely or partially square-rigged. The foremast of each is always entirely square-rigged; variations in the taller mainmast are what define the different subtypes .
Full-rigged brig
For the full-rigged brig, the foremast and mainmast each has three spars, all of them square rigged. In addition, the mainmast has a small gaff-rigged sail mounted behind the mainmast.
Hermaphrodite brig
On a hermaphrodite brig, also called a "half brig" and a "schooner brig", the main mast carries no yards: it is made in two spars and carries two sails, a gaff mainsail and gaff topsail, making it half schooner and half brig. If it also carries one or more square-rigged topsails on the mainmast, it is then considered a "jackass brig". Some authors have asserted that this type of sail plan is that of a brigantine.
Brigantine
Like the hermaphrodite brig, a brigantine also has a main mast made in two spars, and its large mainsail is also fore and aft rigged. However, above this it carries two or three square-rigged yards instead of a gaff topsail, and carries no square-rigged sail at all on its lowermost yard of its mainmast.

Snow

Although superficially similar in appearance to the brig or brigantine, the snow is a much older three masted design which evolved from the larger fully rigged ship. The foremast and mainmast are both square-rigged, but the fore and aft rigged spanker sail is attached to a small trysail mast stepped directly behind the mainmast. This "snow-mast" allows the gaff to raised unhindered by the mainmast and higher than the main yard, which in turn also allows the snow to fly a main course without complications.

Three-masted vessels

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 than a full-rigged ship, especially downwind, but requiring fewer sailors than a full-rigged ship. Optimum rig for transoceanic voyages. This is a classic windjammer rig.

Barquentine or Schooner Barque

A three-masted vessel, square-rigged on the foremast and fore-and-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.

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.

Fully rigged or ship-rigged ship

Three or more masts, square-rigged on all, usually with stay-sails between masts. Occasionally the mizzen mast of a ship-rigged ship would have a fore-and-aft sail as its course sail, but in order to qualify as a "fully rigged ship" the vessel would need to have a square-rigged topsail mounted above this. The classic ship rig originally had exactly three masts, but later, four- and five-masted ships were also built. The classic sailing warship—the ship of the line—was full rigged in this way, because of high performance on all points of wind. In particular, studding sails or topping sails could be easily added for light airs or high speeds. Square rigs have twice the sail area per mast height compared to triangular sails, and when tuned, more exactly approximate a multiple airfoil, and therefore apply larger forces to the hull. Windage is more than triangular rigs, which have smaller tip vortices. Therefore, historic ships could not point as far upwind as high-performance sloops. However, contemporary Marconi rigs were limited in size by the strength of available materials, especially their sails and the running rigging to set them. Ships were not so limited, because their sails were smaller relative to the hull, distributing forces more evenly, over more masts. Therefore, due to their much larger, longer waterline length, ships had much faster hull speeds and could run down or away from any contemporary sloop or other Marconi rig, even if it pointed more upwind. Schooners have a heavier rig and require more ballast than ships, which increases the wetted area and hull friction of a large schooner compared to a ship of the same size. The result is that a ship can run down or away from a schooner of the same hull length. Ships were larger than brigs and brigantines, and faster than barques or barquentines, but required more sailors. Also called "ship-rigged".

Sail-plan measurements

Every sail plan has maximum dimensions. These maxima are for the largest sail possible and they are defined by a letter abbreviation.