If the tack line angles off to leeward, the tack needs to come back down. If it goes straight up or moves to weather, you have good rotation. The vertical angle of the tack line is the visual key.
How high you fly the tack is a matter of wind velocity and angle. If you’re sailing tight angles—have 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 rotate to weather.Easing the tack line opens up the shoulders and more projected area. Look at the upper luff – when it’s trimmed right, the luff is coming around and curling in slightly. Fly it like a normal symmetric spinnaker where the shoulders open up and out, like raising the pole. If the luff gets too bouncy, bring the tack line down.
In the J-105 class, the 77-sqm spinnaker had a luff length that was really short – if you pull the tack all the away down to the pole it would tighten the luff too much and the asymmetric wouldn’t rotate. It must be eased about 60cm. The new 89-sqm chute is better with its longer luff.
On the J-80, the luff length is relatively longer, so it’s not as necessary to ease the tack to get rotation. Initially set the tack line all the way down. 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 10cm.
The Melges 24 gets up on a plane quickly – don’t spend much time adjusting the tack line. If you want to go deep in the 6 to 10 knot range keep the tack line upright or to weather. Keep the tack line firm as you end up steering about a lot to surf or soak down.