It is named after its inventor, Briggs Cunningham, a victorious America's Cup skipper, who was a yacht builder and sailor, as well as being a racecar enthusiast, driver, team owner, and racecar owner and builder. The yacht, Columbia, was led to victory by Cunningham in the America Cup competition of 1958. Briggs was inducted into the America Cup Hall of Fame in 1993. He is also in the international and American motorsports halls of fame and when innovating devices for yachting, called on the specialized talents of automobile racing friends to solve problems such as metal stress and selection.
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 or boom below the foot of the mainsail. It is then passed through a cringle 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.
The tension in the luff of the sail is adjusted using a combination of the halyard 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 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.