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Sail twist is a phenomenon in sailing
Sailing

Sailing is the art of controlling a boat with large pieces of canvas cloth called sails. By changing the rigging, rudder, and dagger or centre board, a sailor manages the force of the wind on the sails in order to change the direction and speed of a boat....
 where the head of the sail
Sail

A sail is any type of surface intended to generate thrust by being placed in a wind—in essence a vertically-oriented wing. Sails are used in sailing....
 is at a different angle of incidence
Angle of incidence

Angle of incidence is a measure of deviation of something from "straight on", for example:* in the approach of a ray to a surface, or* the angle at which the wing or Stabilizer of an airplane is installed on the fuselage, measured relative to the axis of the fuselage....
 from the foot of the sail in order to change the lift distribution with height. Twist is measured by comparing the angle of a straight line between the leading edge (luff) and trailing edge (leech) with that of the boom
Boom (sailing)

In sailing, a boom is a spar , along the Parts of a sail#The edges of a fore and aft rigged sail, that greatly improves control of the angle and shape of the sail....
. Some twist is desirable, but too much can induce weather helm
Weather helm

Weather helm is the tendency of boat to move towards the source of wind, creating an unbalanced helm that requires pulling the tiller windward to counteract the effect....
 or ruin the slot between the mainsail
Mainsail

A mainsail is the most important sail raised from the main mast of a sailing vessel.On a square rigged vessel, it is the lowest and largest sail on the main mast....
 and jib
Jib

A jib is a triangular staysail set ahead of the foremost mast of a sailing boat. Its Tack is fixed to the bowsprit, to the bow , or to the deck between the bowsprit and the foremost mast....
.

Three sail shape controls which control the leech tension, and therefore sail twist, are the mainsheet, the boom vang
Boom vang

A boom vang or kicking strap is a line or piston system on a sailboat used to exert downward force on the Boom and thus control the shape of the sail....
 and the traveler
Mechanical traveller

A mechanical traveller is a moving part of a machine, typically a ring that slides between different positions on a supporting rod when the machine goes through its operating cycle....
.






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Sail twist is a phenomenon in sailing
Sailing

Sailing is the art of controlling a boat with large pieces of canvas cloth called sails. By changing the rigging, rudder, and dagger or centre board, a sailor manages the force of the wind on the sails in order to change the direction and speed of a boat....
 where the head of the sail
Sail

A sail is any type of surface intended to generate thrust by being placed in a wind—in essence a vertically-oriented wing. Sails are used in sailing....
 is at a different angle of incidence
Angle of incidence

Angle of incidence is a measure of deviation of something from "straight on", for example:* in the approach of a ray to a surface, or* the angle at which the wing or Stabilizer of an airplane is installed on the fuselage, measured relative to the axis of the fuselage....
 from the foot of the sail in order to change the lift distribution with height. Twist is measured by comparing the angle of a straight line between the leading edge (luff) and trailing edge (leech) with that of the boom
Boom (sailing)

In sailing, a boom is a spar , along the Parts of a sail#The edges of a fore and aft rigged sail, that greatly improves control of the angle and shape of the sail....
. Some twist is desirable, but too much can induce weather helm
Weather helm

Weather helm is the tendency of boat to move towards the source of wind, creating an unbalanced helm that requires pulling the tiller windward to counteract the effect....
 or ruin the slot between the mainsail
Mainsail

A mainsail is the most important sail raised from the main mast of a sailing vessel.On a square rigged vessel, it is the lowest and largest sail on the main mast....
 and jib
Jib

A jib is a triangular staysail set ahead of the foremost mast of a sailing boat. Its Tack is fixed to the bowsprit, to the bow , or to the deck between the bowsprit and the foremost mast....
.

Three sail shape controls which control the leech tension, and therefore sail twist, are the mainsheet, the boom vang
Boom vang

A boom vang or kicking strap is a line or piston system on a sailboat used to exert downward force on the Boom and thus control the shape of the sail....
 and the traveler
Mechanical traveller

A mechanical traveller is a moving part of a machine, typically a ring that slides between different positions on a supporting rod when the machine goes through its operating cycle....
. The mainsheet pulls the boom (and therefore the foot of the sail) primarily inwards at lower points of sail and downwards at higher points of sail. Manipulation of the traveler can counteract this because it always pulls the boom laterally. The vang on the other hand does the opposite, it always changes the height of the boom.

Computer cut sails can produce the amount of twist specified by the sailmaker
Sailmaker

A sailmaker is a person who makes and repairs sails for sailboats, typically working on shore in a sail loft. Large ocean-going sailing ships often carried sailmakers among the crew....
, and in different conditions, different amounts of twist may be desirable. Less twist is generally desirable in light air conditions and slackening the luff tension will tighten the leech of the sail. This moves the center of effort on the sail toward the trailing edge and reduces twist thus making the sail more powerful but vulnerable to stalling.

See also

  • Angle of incidence
    Angle of incidence

    Angle of incidence is a measure of deviation of something from "straight on", for example:* in the approach of a ray to a surface, or* the angle at which the wing or Stabilizer of an airplane is installed on the fuselage, measured relative to the axis of the fuselage....
  • Wing twist
    Wing twist

    Wing twist is an aerodynamic feature added to aircraft wings to ensure that the wing tip is the last part of the wing surface to Stall , for example when executing a flight dynamics or steep climb; it involves twisting the wingtip a small amount downwards in relation to the rest of the wing....