Flying your Asymmetrical Spinnaker

By Win Fowler

The asymmetrical cruising spinnaker is now a vital part of the modern cruising sail inventory. The design of this sail has come a long way in the past decade, mostly spurred by the advent of cheap computing power on sailmakers' desks. Asymmetricals are now very versatile and forgiving sails and are capable of adding greatly to your boat's performance over a wide range of wind angles.

Trimming these sails should be extremely easy. The cruising asymmetrical is normally tacked to the bow as far forward as a suitable strong point can be found to keep it as clear of the furling gear as possible. Often, the anchor roller, if properly engineered, makes an ideal tack fitting. The tack should be set with the tack about pulpit height, preferably with the tack downhaul adjustable from the cockpit or at least from the foredeck.

The halyard should be as high above and as clear of the forestay as possible and should allow the halyard to pull off to either side without chafe. An external block on a crane is often best.

These sails are usually designed to sheet well aft, even all the way to the quarter. Check with your sail-maker to see where he or she intended the sail to sheet. If in doubt, sheet the sail in fairly tight in a light air and then head up to about 60 degrees apparent wind angle. Now ease the sheet slowly to see where the luff curls first. If the lead is correct, the sail will curl first between 1/3 and ½ way down the luff. If the sail curls first above 1/3 down the lead needs to move ahead, if below the ½ way point, it needs to move aft.As the wind comes aft the sheet should be eased to keep the luff of the sail near the breaking point. If the break point starts getting too high on the luff you may have to move the lead forward to keep the sail from over-twisting, but usually the boom serves to move the lead forward automatically by pushing down on the sheet as the main sheet is eased.

Once the apparent wind gets farther aft than about 120 degrees apparent, the sail may work better if the tack is allowed to rise. This has two effects – first, to allow the sail to roll farther to windward out of the wind shadow of the mainsail and, second, to flatten and untwist the sail. When the sheet is eased very far, even the boom will not hold the lead down enough to prevent the top of the sail from twisting around to weather too far. Raising the tack will restore the twist balance. Likewise, as the sheet is eased the clew gets closer to the luff, making the whole sail fuller. Raising the tack lets the sail bend more in the vertical profile which has the corresponding effect of flattening the sail's sectional shape.

Don't be afraid to play around with the trim settings of your asymmetrical. A little experimentation will do wonders for your downwind speed.

Maine Sailing Partners
www.mesailing.com
1-888-788-SAIL