Sails

Rake and bag

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Pat Connolly, of Chatham, Massachusetts, asks:

"My 23-foot sloop has weather helm. I replaced the hanked-on jib with a furling headsail, but after the furler was installed I had to tighten the backstay to get the sag out of the furling system even though the new forestay was cut to the same length as the old one. The owner’s manual says there should be a mast rake of about 7 inches, but when I ran a line with a plumb bob from the top of the mast to the deck, I saw that the rake was about 18 inches. What can I do to reduce the weather helm?"

Win Fowler replies:

While many factors affect helm balance, mast rake does play a big role. If the rake is more than it should be, the center of effort of the sailplan will move aft and increase weather helm. One of the best ways to reduce weather helm is to shorten the forestay to bring the mast to a more vertical position. Wire will stretch when it is first put under load, and that might account for some of the sag. Still, if the new forestay is the same length as the old one, I’m sure that sag doesn’t account for the additional 11 inches of rake, which you do need to eliminate. Some furling systems can be adjusted for length; if you can shorten yours, I would start there first.

Next look at your main and jib. If either one, but particularly the mainsail, is full in the midsection with a leech that hooks to windward, that shape can also produce significant weather helm. To check your sails, get on a close-hauled course with your main and jib properly trimmed. Position yourself under the boom, midway along the foot, and look up; do the same thing with the jib. You’ll be able to see where the draft is in the sail and whether the leech is hooking to windward. Better yet, take a photo with the luff on one side of the frame and the leech on the other. Take the photos to your sailmaker, who will be able to confirm whether the shape and trim of your sails is contributing to your weather helm.

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