Occasionally, you might find the waves coming well to the side of the boat, almost like you’re reaching.  In this situation, I carry a little more helm than I would in the flat-water mode because, when the wave hits the bow side-on, the additional helm prevents the waves from pushing the bow to leeward. To do that, sheet the main more than normal but leave the jib alone. So, as waves push the bow down, the entire mainsail leech is working to keep the boat up: the mainsail is fighting for you, and that will keep the boat sailing straight.

How much twist do you need?
For most people, the wave mode is the most challenging. As someone who spent a lot of time near the masthead over the past few years [Horton was regularly perched atop Luna Rossa’s mast in the 32nd America’s Cup challenger trials—Ed.], you think about how much the top of the mast is moving. The masthead fly is an indicator of that. Every time the bow goes down a wave, the top of the mast goes forward and the wind comes more from the bow (see diagram on p. 64).You’ll see that movement reflected in the direction of the masthead fly. Then, when the bow comes up and the mast moves aft, the masthead fly will point more to the side. When it’s wavy—and this works on every boat—watch the masthead fly as the boat is sailing upwind. As the boat pitches, the masthead fly will move. If it’s moving a lot, you need lots of depth and twist. If it’s not moving much, you really don’t need much of either.

As I look at the masthead fly moving forward and aft, I try to “freeze-frame” the two extreme positions. I think, “OK, if the wind indicator is all the way back, as in a lift, what would my mainsail look like?” The answer is that it’s like a very close reach, so you’d have the mainsheet eased and a little more depth in the sail.
When the masthead fly is forward, such as when the bow is coming down a wave and the boat appears headed, the sail would ideally be set up with a tighter leech and not much depth. Most boats can’t shift gears that quickly, so think of the sail in thirds. The top portion is the lifted part, when the mast is coming back, the middle is for power, and the bottom is the headed part, when the mast is moving forward. With that setup, part of the sail is always trimmed for the range of wind you’re seeing. The top of the sail is trimmed for the “reach” situation, the bottom for the “header situation,” and the mid-leech for anything in between.

If you hit a wave, stop, and don’t accelerate very quickly, you’re probably not twisting enough. Shift into the wave mode. Another reason to move to the wave mode is when you need to be able to steer to avoid the big waves, but every time you try to put the bow down to accelerate, the boat heels way over. The flat-water setup won’t allow that amount of course variation.

When do you move back to the flat-water setup? As the boat pitches and the apparent wind changes, watch where the sail starts luffing, or breaking up. When the mast moves forward and your sail breaks up just at the top, then it’s probably too full and too twisted. And if you’re fighting to keep the boat on track because of waves coming from the side, it’s time for the flat water mode.

As a rule of thumb, I try to set up the sails with the least amount of twist that I can get away with. I’m not going to go out with a flat-water setting if it’s blowing 20 knots with waves on the bow. Inevitably, what will happen when you twist too much is that you won’t point as high. If you’re looking at photos, a good indicator that you’re twisting too much is that the middle leech has moved to leeward. This is tough to see from onboard.

When you’re two-boat testing before a race, and you’re sailing on the tack that takes you more into the waves, be sure to give it some time. Waves really affect boat speed. You can’t just sail for 30 seconds and say, “We’re faster than that guy” or “We’re slower than that guy.” One bad wave will stop you, and one bad wave will stop the other boat. You have to go through that whole cycle of stopping, accelerating up to speed, and pointing a few times to figure out who’s actually set up correctly.

Keep in mind the two modes and how to get there. Always add depth when you’re twisting the sails. And remember, both sails work in harmony. If you adjust one, you should definitely be adjusting the other.