Fly an asymmetric spinnaker faster

Want to get more speed out of your asymmetric spinnaker and become more comfortable racing with this type of sail? Many points given in this article suggest the subtle things you can do to make your boat faster downwind.

Crew Positions

One of the most important things downwind is to keep the spinnaker away from the very large main. In extremely light air the crew is placed by the shrouds on the downwind side of the boat. This will help the spinnaker stay away from the mast on the leward side of the boat. In medium heavier air, heeling the boat to windward helps the spinnaker separate from the main because it projects the luff to the windward side of the boat. This is why you see the top boats in an asymmetric fleet sailing downwind with the whole crew packed to weather by the shrouds. The J/120 design has a very full bow and it likes the weight forward downwind. The goal in weight placement is to reduce wetted surface, but not to plow the bow too much or lose control so it less important in very heavy air to have the weight forward as it is to keep the rudder in the water.

Mast Position

One the most important things to do is pulling the rig forward when sailing downwind. This alone can have a huge effect on boat speed because it projects the spinnaker away from the mainsail into clearer wind. Ease off your backstay for starters. To get the rig farther forward still, use your spare spinnaker halyard to pull the rig forward. After the jib or genoa comes down, the bowman hooks the halyard to the tack fitting and halyard trimmer grinds the rig forward. We call this technique fraculating. You'll be amazed how much farther forward the rig will go. You will also greatly reduce the pumping of the mast and get every bit of wind power to go faster.

Spinnaker Trim

The important goal is to trim your sails to further increase separation between spinnaker and mainsail. The trimmer's goal should be to ease the sheet as much as possible, allowing the spinnaker to lift and float away from the main.

Another thing to pay attention to is the trim of the spinnaker's tack line. If the luff of an asymmetric becomes too bouncy or hard to control, tighten the tack line. After we build speed and the pressure increases in the sail, we usually try easing the tack line to allow the chute to float away from the main and rotate to windward. I like to call this effect on an asymmetric "opening the luff." When the luff opens and the sail lifts away from the boat, the upper sections of the luff are more pressured, and the luff flattens in curvature slightly. This is OK, because the spinnaker has pressure in it and remains stable while rotating to windward more and separating from the mainsail. If you have enough wind you can ease the tack line out 3 to 4 feet. In conditions where the wind speed drops and increases quite often we will have a crewmember stationed at the tack line adjustment to optimize flow over the spinnaker.

Here's a general rule of thumb for tack-line tension: if the tack line is angled to leeward or if the luff of the sail becomes unstable, tighten the tack line; if the tack line is angled to windward and you want to try to open up the upper luff, ease the tack line.

In light air in flat water under 10 knots apparent we like to have the halyard out from 6" to 12". When preparing to gybe it is important to have the tack line and halyard in tight. This prevents the tack line wrapping around the sprit. If you are under 2 knots of air and lose all pressure in the spinnaker we have been also successful dropping the main completely.

Mainsail Trim

Another important factor in downwind speed with an asymmetric is how you trim the mainsail. The primary rule is to avoid over trimming the main. Check the trim simply by easing the main until the luff starts to break and then bring it in until it stops breaking. The vang should also be tensioned.

Crew Work

Commonly we need a person to hold the boom so that it does not move. We also use this person to spot coming wind gusts and changes of direction. The spotter also helps with tactical decisions, such as how to keep our lane clear and free from any wind shadows, and how to take advantage of wind shifts or different sailing angles coming into the leeward mark.

Another position is that of the spinnaker trimmer, whose main job is to help the helmsman sail the boat at the optimum sailing angle for the best VMG to the leeward mark. The trimmer's goal should be to keep the sheet as eased as possible without the luff of the sail breaking. An equally important job is to constantly inform the helmsman of the pressure on the sheet and in the sail. I find the trimmer's advice most helpful when he repeatedly suggests how much or how little pressure is in the sail. He might say, for example, "I'm losing pressure in the sail" or "I have a lot of pressure." On J/120's, the trimmer position becomes a team effort, with the grinder and trimmer working together to keep the sail in optimum trim while communicating with the helmsman. The helmsman should keep an eye on boat speed. When the speed drops too low he should inform the crew that he will be "heating up" or "burning off speed" when the boat is pointing too high for the current wind speed. I have seen too many J/120's head too low or too high and in the long run lose ground to others.

Other Tips

When going into a windward mark, ask yourself if you're on a lift or a header. That will help you decide which tack you want to take down the run—typically, the headed jibe. And use a hand-bearing compass to help sight the leeward mark and then determine when to jibe.

Work hard to keep your air clear and avoid sailing under the fleet; it is easy for boats behind to trap you and blanket you. In front of other boats J/120's have the speed of a brick. Keep that clear air. When you jibe, try to make every one of them count. Each jibe results in a loss in distance, so while you should take advantage of the shifts, don't jibe just for the sake of jibing, especially in light air. air.

Finally two things are important. First, nothing beats practice. You need to develop that team cohesion that is critical on any boat. Second, you should try to benchmark these techniques against other J/120's. It is the only way to tell if what you are doing is right for those conditions.