A backstay is a piece of standing rigging on a

sailing Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, windsurfer, or kitesurfer), on ''ice'' (iceboat) or on ''land'' ( land yacht) over a chose ...

vessel that runs from the

mast Mast, MAST or MASt may refer to: Engineering * Mast (sailing), a vertical spar on a sailing ship * Flagmast, a pole for flying a flag * Guyed mast, a structure supported by guy-wires * Mooring mast, a structure for docking an airship * Radio mas ...

to either its transom or rear quarter, counteracting 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 ...

and jib. It is an important sail trim control and has a direct effect on the shape of the

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 ...

and the

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 ...

. Backstays are generally adjusted by

block and tackle A block and tackle or only tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift heavy loads. The pulleys are assembled to form blocks and then blocks are paired so that one is fixed and on ...

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counte ...

adjusters, or lines leading to winches.

Types

Backstays may be ''permanent'' or ''running''. A permanent backstay is attached to the top of the mast. Running backstays appear in pairs attached about two-thirds of the way up the mast (sometimes at multiple locations along the length of the mast). In general, most modern sailboats have a permanent backstay and some have a permanent backstay combined with running backstays. Backstays are not always found on all vessels, especially smaller ones. A permanent backstay is attached at the top of the mast and may or may not be readily adjustable. 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, ...

, tensioning the permanent backstay directly tensions the forestay. This control is used to adjust the amount of "sag" in the headsail. In a

fractional rig A fractional rig on a sailing vessel consists of a foresail, such as a jib or genoa sail, that does not reach all the way to the top of the mast. The forestay is a wire that secures the mast to the front of the boat. With a fractional rig, th ...

, tensioning the permanent backstay has two effects: First, the forestay is tensioned (controls sag in headsail) and second, the mast bend is increased, particularly in the upper one-half to one-third of the mast. Increased mast bend tends to reduce the draft ( camber) of the mainsail. A running backstay always attaches to the mast at a point below the top of the mast and is generally used in conjunction with a permanent backstay. Running backstays are found on both masthead rigs and fractional rigs. There are some rigs for which running backstays may be used without a permanent backstay. This occurs most often where the mainsail has a significant

roach Roach may refer to: Animals * Cockroach, various insect species of the order Blattodea * Common roach (''Rutilus rutilus''), a fresh and brackish water fish of the family Cyprinidae ** ''Rutilus'' or roaches, a genus of fishes * California roa ...

or a very large mainsail, especially combined with narrow hull beam.

Gaff rigged 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 ...

boats invariably have running backstays with no permanent backstay. In both of these cases the mainsail extends aft of a line from masthead to stern, and so a permanent backstay would interfere with the operation of the sail. As a direct consequence of its attachment point (below the top of the mast) a running backstay is always adjustable because it must be manually engaged and disengaged during every

tack TACK is a group of archaea acronym for Thaumarchaeota (now Nitrososphaerota), Aigarchaeota, Crenarchaeota (now Thermoproteota), and Korarchaeota, the first groups discovered. They are found in different environments ranging from acidophilic ...

jibe A jibe (US) or gybe (Britain) is a sailing maneuver whereby a sailing vessel reaching downwind turns its stern through the wind, which then exerts its force from the opposite side of the vessel. Because the mainsail boom can swing acros ...

. Adjusting the tension on the running backstay has two effects: First, the forestay is tensioned (controls sag in headsail) and Second, mast bend is increased (the mast becomes more bent). The overall effect of tensioning the running backstay is a shallower mainsail (less camber) combined with a reduction in headsail sag. If the running backstays lead to the mast where the forestay attaches, the effect of tensioning them is to reduce sag in the headsail, increase mast bend, and flatten the mainsail as a result. Both effects are desirable as the wind increases.

Backstays as antennas

On modern oceangoing yachts, the backstay is also commonly used as an antenna for Marine SSB radios and/or an

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency commu ...

, accomplished by placing structural

backstay insulators Backstay insulators, when used as a pair, are devices which allow for the electrical isolation of a section of wire on a yacht (e.g. the backstay) so that it can be used as an antenna for a single sideband (SSB) radio. Since these insulators form ...

at either end of the backstay.

References

{{Sail Types Sailing rigs and rigging