In sailing

Sailing

Sailing is the propulsion of a vehicle and the control of its movement with large foils called sails. By changing the rigging, rudder, and sometimes the keel or centre board, a sailor manages the force of the wind on the sails in order to move the boat relative to its surrounding medium and...

, a cunningham or cunningham's eye is a type of downhaul

Downhaul

The downhaul is a line which is part of the rigging on a sailboat; it applies downward force on a spar or sail. The most common downhaul on a modern sailboat is attached to the spinnaker pole, though this may be referred to as the foreguy in some rigging nomenclature...

 used on a Bermuda rigged sailboat to change the shape of a sail. Sailors also often refer to the cunningham as the "smart pig".

It is named after its inventor, Briggs Cunningham

Briggs Cunningham

Briggs Swift Cunningham II was an American entrepreneur and sportsman, who raced automobiles and yachts. Born into a wealthy family, he became a racing car constructor, driver, and team owner as well as a sports car manufacturer and automobile collector.He skippered the victorious yacht Columbia...

, a victorious America's Cup

America's Cup

The America’s Cup is a trophy awarded to the winner of the America's Cup match races between two yachts. One yacht, known as the defender, represents the yacht club that currently holds the America's Cup and the second yacht, known as the challenger, represents the yacht club that is challenging...

 skipper and yacht

Yacht

A yacht is a recreational boat or ship. The term originated from the Dutch Jacht meaning "hunt". It was originally defined as a light fast sailing vessel used by the Dutch navy to pursue pirates and other transgressors around and into the shallow waters of the Low Countries...

 builder.

The cunningham differs from a typical downhaul in the way that it attaches to the sail. The system usually consists of a line which is secured at one end to the mast

Mast (sailing)

The mast of a sailing vessel is a tall, vertical, or near vertical, spar, or arrangement of spars, which supports the sails. Large ships have several masts, with the size and configuration depending on the style of ship...

 or boom

Boom (sailing)

In sailing, a boom is a spar , along the foot of a fore and aft rigged sail, that greatly improves control of the angle and shape of the sail. The primary action of the boom is to keep the foot of the sail flatter when the sail angle is away from the centerline of the boat. The boom also serves...

 below the foot of the mainsail. It is then passed through a cringle

Cringle

A cringle is an eye through which to pass a rope. In nautical settings, the word refers to a small hole anywhere along the edge or in the corner of a sail, rimmed with stranded cordage and worked into the boltrope. Typically it encloses a metal grommet for reinforcement and to reduce wear...

 in the luff of the sail near the foot, but above the tack, and then led down on the other side to a fitting on the mast or boom or on deck

Deck (ship)

A deck is a permanent covering over a compartment or a hull of a ship. On a boat or ship, the primary deck is the horizontal structure which forms the 'roof' for the hull, which both strengthens the hull and serves as the primary working surface...

.

The tension in the luff of the sail is adjusted using a combination of the halyard

Halyard

In sailing, a halyard or halliard is a line that is used to hoist a sail, a flag or a yard. The term halyard comes from the phrase, 'to haul yards'...

 and the cunningham (where fitted). The primary advantage of adjusting the cunningham is the speed and ease with which the luff tension can be changed while sailing or racing. By hauling or easing the line, the tension in the luff can be changed, thereby shifting the point of maximum draft

Draft (sailing)

In nautical parlance, the draft or draught of a sail is a degree of curvature in a horizontal cross-section. Any sail experiences a force from the prevailing wind just because it impedes the air's passage...

of the sail forward or aft, optimizing sail shape—and therefore—performance. It is a fine control which is used more frequently on racing sailboats than on cruising or day-sailing boats.