The sheeting distance (SD) is the distance from the tack to the genoa car for equal tension on the foot and leech of the headsail. It is the intersection of a line from the centriod of the sail through the clew with the genoa track. Moving the car forward from this position will tighten the leech and loosen the foot while moving the car aft does the opposite. This is a theoretical value based on the sail dimensions and the shear angle of the gunwale but it does illustrate that the factory genoa tracks were too short to properly sheet any but the largest genoas (>150%). The forward end of the factory track was 19 feet from the tack point. In practice the sails sheet ahead of this calculated SD by about 5-10%.
Sail Plan Drawing