Notes on Jib Sheet Lead
The sheet used to control the jib must be led to a point on the boat which affords optimum setting of the jib. The optimum setting is difficult to describe, but easy to feel. When the jib lead is at its best location, the sail will set with minimum wrinkle and have an obvious “grip” on the wind. If a Genoa is used, a separate sheet lead must be determined for this sail also. Since the jib sheets are in two parts (one for starboard, one for port), a lead point will be located on each side of the boat.
In determining the lead points, the designer probably uses a formula (like the one below) which is at best only an approximation. Because this method is an approximation, and because no two sails will trim exactly the same, it is best to make the sheet lead point adjustable by using a track and sliding fittings. Another method for determining the jib lead, at least on small boats, is to sail the boat with the jib in position and thereby determine the optimum setting. When the optimum setting has been located, mark with a pencil and attach the appropriate fitting on the deck.
A common method for determining jib and Genoa leads is shown above. Extend a line from 40% above the tack of the sail, through the jib clew. While keeping the line straight, move the end of the line in an arc. Where the arc intersects a line 10o or 12o-14o off the centerline is the location of the center of the jib track.