The Commandments of Asym Trim
The Commandments of Asym Trim
Guidelines on trimming your asymmetrical chute.
Ask a group of sailmakers how to toast a piece of white bread and you'll get as many different answers as there are sailmakers in the room. Invariably, they'll tell you that it depends on the kind of bread, the toaster, and its heating elements. The same is true when breaching the topic of asymmetric spinnaker trim. However, while their trimming tips have lots of subtle variations, they ultimately boil down a few fundamental rules. We put the topic before a handful of asymmetric trim experts-Jay Lutz, of North; Kerry Klingler, of UK, Dave Ullman, of Ullman Sails, Richard Bouzaid, of Doyle, and Scott Nixon, of Quantum-who tell us that asymmetric trim is not much different than it was five years ago, the one exception, of course, is that the sails are better designed to do what they're supposed to do-get you down the run faster.
Commandment No. 1. Thou shall rotate your asymmetric to weather.
Lutz: "A well-designed running spinnaker can rotate around and away from the blanket effect of the mainsail, which allows you to sail low without collapsing the sail. The keys to getting it to rotate are crew weight and the shape of the sail. Both work in conjunction. If you can get the boat to heel to weather, gravity naturally helps rotate the sail. Today's runner asymmetric-if it has enough luff round [the shape of the curve designed into the luff of the sail] designed in-naturally wants to rotate when it fills. It's more genoa-like, with the draft far forward.
Klingler: "We're designing so much positive luff round that the dynamics of the sail pull the draft forward dramatically. As a result they rotate better, and as they do, that puts the draft even more forward in the sail, which is where you want it to be. But you still need to pack the crew on the weather rail to get it to rotate well.
Commandment No. 2. Thou shall keep the tack line in mind.
Bouzaid: One of the problems with the centerline sprit-flown asymmetric sails is that as you start sailing deeper the sail wants to rotate and the luff effectively becomes shorter. Unless you ease the tack up it won't float away from the front of the boat. When the spinnaker naturally starts rotating to windward it's a good time to ease the tack line.
Ullman: How high you fly the tack is a matter of wind velocity and angle. If you're sailing relatively tight angles-trying to go fast forward-you want the tack all the way down and the luff as straight as possible. If you're trying to go deep, you want the spinnaker to rock (rotate) to weather. How much to ease is gut feeling and eyesight. The rule we use is that anytime you ease the tack line and it's angled to weather, that's good. If it goes to leeward at all, you're losing projected area. The whole goal is to get the spinnaker to go in front of the boat farther. If you ease too much, the head gets too parallel to the water and you start losing area (basically making the sail smaller and not spreading it out.) In J/105s, we recommend no more than 2.5 feet of ease (with our sail), but every spinnaker will be different. There's not a lot of science to trimming them. If you're at 90 to 110 degrees apparent wind angle, then you want the tack down and trim as loose as possible. As you go deeper than that, start easing the tack as it starts rotating to weather and ease the sheet as far as possible.
Klingler: If you have the boat heeled properly, and you have the right pressure in the sail, easing the tack line opens up the shoulders and gives you more projected area. It also flattens out the luff a little and moves the draft to the middle of the sail a little bit. The thing you're looking at is the upper luff; when it's trimmed right, the luff is coming around, sort of cupped and hinging in slightly. Fly it like a normal symmetric spinnaker where the shoulders open up and out, like it does when you raise the pole on a regular spinnaker. If the luff gets too bouncy, bring the tack line down. If it's too easy to fly, ease it up. The deeper you try to sail the more you can ease it, but trim it again as you change your angle to sail higher. In other words, adjust it often.
Lutz: Everyone's letting off tack lines. The reason you're really doing it is to increase the luff length on the sail, and with a longer luff length, you can rotate the sail farther to weather. That's absolutely true, but there's more to it. In the J/105 class, the 77-square-meter spinnaker had a luff length that was really short, so if you pulled the tack all the away down to the pole it would tighten the luff too much and the spinnaker wouldn't rotate (the new 89-square-meter chute is better with a longer luff). On the J/80, the luff length is much longer relatively, so it's not as necessary to ease the tack to get rotation. When you first raise the J/80 chute, you set the tack line all the way down. The only time you would ease it off is if your particular sail design is a little short in the luff. In really flat water and medium air, where you're trying to sail low for tactical reasons, you can ease the tack line as much as 5 inches. On the J/105, it's a couple of feet. Here's a rule of thumb: if you let the tack line off and the line angles off to leeward, the tack needs to come back down. If you let it off and it goes straight up or moves to weather, you have good rotation. The vertical angle of the tack line is the visual key of whether or not you have it right.
Nixon: The Melges 24 gets up on a plane so quick that we don't spend much time adjusting the tack line, but there are a couple of conditions when you start soaking deep enough in the 6- to 10-knot range where you might-as long as the tack is straight up or to weather. We keep the tack line firm because in boats like the Melges you end up steering the boat a lot to either get up on a surf or soak down; with the tack down it's easier to steer the boat to the kite. Having it down makes the luff of the sail more stable, too. In the light stuff we keep it down as well because we're sailing tight angles-if you let it off, the sail will fall behind the main.