As you rotate aft (decrease rotation), you bend the mast more along its major (long) axis with increasing sheet tension. This tends to do a couple of things.

1. It decreases leech twist.
2. It flattens the sail more evenly top to bottom because the mast is bending more evenly top to bottom.
3. It provides a better shape for speed especially in flat water.

Keep in mind that as you sheet tighter with the rotation more aft, you need to pull on more downhaul to keep the draft of the sail from moving too far aft and to help open up the top of sail. This will depower the top of the sail first where it should be depowered. Most crews want the top of the sail to "go away" in typically over 14 knots of wind.


As you rotate forward (increase mast rotation), you bend the mast more along its minor (short) axis with increasing sheet tension. This tends to do a couple of things.

1. It bends the mast more at the top than in the mid to lower sections.
2. It flattens the sail more at the top and keeps it fuller in the lower to mid sections.
3. It provides a better shape for power especially in chop.

Easing the downhaul will keep the draft in the right position and keep the top of the sail from getting too open. A typical scenario might have you 50-100 yards from the weather mark and just barely fetching. Try rotating forward 5-10 degrees and ease off the downhaul about 1/2". It'll feel like downshifting into a lower gear.

If you are sailing upwind and the wind shifts to where you are going more into the waves on one tack and more across the waves on the other tack, the rotator can be a powerful tool as you can rotate more aft on the tack going across the waves because there is less resistance and rotate more forward on the other tack to power the boat through the waves coming more direct on your bow.

Fun stuff.

Bob Hodges
A-Class USA 230