A fractional rig on a sailing vessel consists of a

foresail A foresail is one of a few different types of sail set on the foremost mast (''foremast'') of a sailing vessel: * A fore-and-aft sail set on the foremast of a schooner or similar vessel. * The lowest square sail on the foremast of a full-rig ...

, such as a

jib A jib is a triangular sail that sets ahead of the foremast of a sailing vessel. Its tack is fixed to the bowsprit, to the bows, or to the deck between the bowsprit and the foremost mast. Jibs and spinnakers are the two main types of headsail ...

or genoa sail, that does not reach all the way to the top of the mast. The

forestay On a sailing vessel, a forestay, sometimes just called a stay, is a piece of standing rigging which keeps a mast from falling backwards. It is attached either at the very top of the mast, or in fractional rigs between about 1/8 and 1/4 from the t ...

is a wire that secures the mast to the front of the boat. With a fractional rig, the forestay is attached between about 1/8 and 1/4 of the length of the mast lower down, rather than being attached to the top of the mast as in a

masthead rig A masthead rig on a sailing vessel consists of a forestay and backstay both attached at the top of the mast. The Bermuda rig can be split into two groups: the masthead rig and the fractional rig. The masthead rig has larger and more headsails, ...

. The foresail (jib or genoa) is then rigged to this

stay Stay may refer to: Places * Stay, Kentucky, an unincorporated community in the US Law * Stay of execution, a ruling to temporarily suspend the enforcement of a court judgment * Stay of proceedings, a ruling halting further legal process in a tri ...

. The mast is farther forward on the boat than on a

and so it has a larger

mainsail A mainsail is a sail rigged on the main mast of a sailing vessel. * On a square rigged vessel, it is the lowest and largest sail on the main mast. * On a fore-and-aft rigged vessel, it is the sail rigged aft of the main mast. The sail's foot i ...

. Masthead rigs are most common on larger

keelboats A keelboat is a riverine cargo-capable working boat, or a small- to mid-sized recreational sailing yacht. The boats in the first category have shallow structural keels, and are nearly flat-bottomed and often used leeboards if forced in open w ...

or cruisers. A fractional rig is typically used on sailing

dinghies A dinghy is a type of small boat, often carried or towed by a larger vessel for use as a tender. Utility dinghies are usually rowboats or have an outboard motor. Some are rigged for sailing but they differ from sailing dinghies, which ...

and racing oriented keelboats, such as the J/24. Fractional rigs were introduced on race boats in order to allow more controllability of the surface of the mainsail and also less drag when sailing upwind. According to one manufacturer, "a key to making fast boats easier to sail than slow boats is the 'fractional rig'". Fractional rigs tend to have a larger mainsail and a smaller

headsail A sail plan is a description of the specific ways that a sailing craft is rigged. Also, the term "sail plan" is a graphic depiction of the arrangement of the sails for a given sailing craft.> In the English language, ships were usually describe ...

which is often a non-overlapping jib. This configuration is optimized for upwind sailing efficiency. For downwind sailing without a spinnaker, the larger mainsail of a fractional rig has a significant advantage over a masthead rig but a disadvantage when spinnakers are flown. Many newer high-performance fractional rig sailboats, fly the spinnaker or the

gennaker A gennaker is a sail that was developed around 1990. Used when sailing downwind, it is a cross between a genoa and a spinnaker. It is not symmetric like a true spinnaker but is asymmetric like a genoa, but the gennaker is not attached to the f ...

from the masthead. On many modern skiffs and race dinghies, the jib is relatively small compared to the size of the main and it is normally left in place when the spinnaker or gennaker is used due to this type of jib's minimal aerodynamic interference. Another major advantage of the fractional rig, especially the '3/4' rig (where the fore stay goes 3/4 the way up the mast), is that the jib can be taken in without inducing excessive weather helm which could cause the boat to lose control and “round up” into the wind. With the masthead sloop, both the main and the jib must be reduced in size evenly when shortening sail. This is typically accomplished by

reefing Reefing reduces the area of a sail, usually by folding or rolling one edge of the canvas in on itself and attaching the unused portion to a spar or a stay, as the primary measure to preserve a sailing vessel's stability in strong winds. Restoring ...

the main and either rolling up a portion of the headsail on a furler, or changing to a smaller headsail. Since jibs need considerable forestay tension to set properly and the amount of tension needed increases with wind speed, being able to drop the jib altogether in windy conditions puts less strain on the rig and hull. Fractional rigs are used on lightly built

multihulls A multihull is a boat or ship with more than one hull, whereas a vessel with a single hull is a monohull. The most common multihulls are catamarans (with two hulls), and trimarans (with three hulls). There are other types, with four or more hul ...

for this reason.

History

Throughout the 20th century, most

sloops A sloop is a sailboat with a single mast typically having only one headsail in front of the mast and one mainsail aft of (behind) the mast. Such an arrangement is called a fore-and-aft rig, and can be rigged as a Bermuda rig with triangular ...

of less than 20 feet in length had fractional rigs. Many (perhaps most) sailing sloops from the first part of the 20th century were fractional rigged. The increased prevalence of fractional rigs on sloops in the early 20th century probably coincided roughly with the disappearance of the

gaff rig Gaff rig is a sailing rig (configuration of sails, mast and stays) in which the sail is four-cornered, fore-and-aft rigged, controlled at its peak and, usually, its entire head by a spar (pole) called the ''gaff''. Because of the size and shap ...

. One possibility for its increased prevalence during this era is that, relative to a masthead rig, it allows the designer to provide the boat with more sail area without using a

bowsprit The bowsprit of a sailing vessel is a spar extending forward from the vessel's prow. The bowsprit is typically held down by a bobstay A bobstay is a part of the rigging of a sailing boat or ship. Its purpose is to counteract the upward tensio ...

or a

boom Boom may refer to: Objects * Boom (containment), a temporary floating barrier used to contain an oil spill * Boom (navigational barrier), an obstacle used to control or block marine navigation * Boom (sailing), a sailboat part * Boom (windsurfi ...

that extends beyond the stern, and without demanding that the sails be of a very high aspect ratio. This was important because the

sailcloth Sailcloth encompasses a wide variety of materials that span those from natural fibers, such as flax, hemp or cotton in various forms of sail canvas, to synthetic fibers, including nylon, polyester, aramids, and carbon fibers in a variety of wov ...

available in those days made it difficult to construct high-aspect sails. As sailcloth improved in the second half of the 20th century, it became possible to construct sails of a higher aspect ratio. It therefore became more practical for sloops to be designed with the simpler masthead-rigged mast. Most production sailboats from the '60s and '70s were masthead-rigged sloops. Masthead-rigged sloops typically carry a larger spinnaker than fractional-rigged sloops, and therefore enjoy a speed advantage when racing downwind. Fractional rigged sloops are starting to become popular again, especially for high-performance racing boats. A fractional rig allows the mast to bend more easily, which in turn allows more adjustment to the shape of the mainsail, especially when sailing upwind. Many people believe that a fractional-rigged sloop is faster upwind than a similar masthead-rigged sloop, especially as the wind strength increases. Most of the newest generation of fractional-rigged sloops fly their spinnakers from the top of the mast. These boats are said to have "masthead spinnakers" and this development gives the boat very good performance both upwind and downwind in all wind strengths.

Maintaining forestay tension

An inherent problem of a fractional rig is its inability to exert as much tension on the forestay as a similar masthead rig. The reason for this is because the attachment point of the forestay is not directly opposite to the

backstay A backstay is a piece of standing rigging on a sailing vessel that runs from the mast to either its transom or rear quarter, counteracting the forestay and jib. It is an important sail trim control and has a direct effect on the shape of the ma ...

. Under certain conditions, the moment arm that results from these offset attachment points can be used to advantage as this is an effective method of inducing bend in the mast which in turn flattens the mainsail. If the distance between the attachment points is too great, a mast of average stiffness will be unable to apply optimum forestay tension, unless one of the following mast-stiffening design features is used: * Jumper stays — These additional stays and their associated jumper struts limit the amount that the upper portion of the mast can bend and thereby enable tension to be effectively transferred from the backstay to the forestay. Jumper stays were common in the first part of the 20th century. Their biggest disadvantage is weight and

windage Windage is a term used in aerodynamics, firearms ballistics, and automobiles. Usage Aerodynamics Windage is a force created on an object by friction when there is relative movement between air and the object. Windage loss is the reduction in ...

aloft. * Running backstays — These are supplemental temporary backstays (one on each side) that attach opposite of the forestay. They are very effective at generating forestay tension, but make the boat more difficult to tack because one running backstay needs to be released and the other one applied each time the boat tacks. * Swept back spreaders — Swept back spreaders (or rather their associated

shrouds Shroud usually refers to an item, such as a cloth, that covers or protects some other object. The term is most often used in reference to '' burial sheets'', mound shroud, grave clothes, winding-cloths or winding-sheets, such as the famous S ...

, which attach to the deck significantly aft of the mast) provide significant fore-and-aft support to the mast and thereby increase tension in the forestay. The biggest disadvantage of this scheme is that it makes it difficult to deliberately slacken the forestay for the purpose of making the jib fuller in light winds.

Reference list

{{DEFAULTSORT:Fractional Rig Sailing rigs and rigging