Step 4:

Set twist and depth with fore-and-aft lead position

The fore-and-aft position of the genoa has a significant effect on twist and depth in the foot. Remember that twist is the change in chord angles (relative to the foot) from the bottom to the top of the sail, and is necessary because of wind twist aloft due to gradient and (sometimes) sheer. When sail twist matches wind twist, the genoa is perfectly trimmed from top to bottom. Now the sail should luff simultaneously up and down the luff when you head up slowly past close-hauled. Set your lead position by luffing up slowly and watching your telltales. The wind- ward telltales should "break" evenly from top to bottom at the same time.

If the top telltales flutter before the bottom, the sail is twisted too much. Move the lead forward to pull down on the clew, increase leech tension and reduce twist. If the bottom telltales luff first (or the top ones stall), the sail needs more twist. Move the lead aft to relax leech tension.

Moving the genoa lead position also affects foot depth, much as the outhaul controls foot depth on a mainsail. To add depth, move the lead forward. This shortens the distance from clew to tack, and moves the foot of the sail farther away from the chainplates. (The upper two-thirds of the genoa will keep about the same shape.)

Use your Sailscope to measure the depths of your sail at each of the three draft stripes (the middle one is most important).

When the upper windward telltale lifts before the others, the genoa has too much twist, and the lead should be moved forward until all the telltales behave consistently.
The table below gives approximate target depths for the various genoas. If your boat has an unusual sailplan, hull shape or sheeting angle, these suggested depths might not work.


» Set depth and twist with backstay