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post #2 of Old 03-12-2004
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Furling Main Sails

To some extent it depends on the installation and the particular model boat, but in talking to sailmakers and people who have used them, and reading an evaluation by a regional PHRF authority, I have drawn some conclusions.

To begin with, I talking with people who have in mast furling, most really love the system, until the first time it locks up in a heavy wind. They do lock up and they can be a real problem to clear. I have heard separate two stories, where to save the boat they literally sent someone up the mast to cut away the sail in a blow. With jib roller furling there are a variety of options for dealing with a jamb. Those options are not available on in-mast furling. On that basis alone I would say that in-mast furling is not a suitable set up for offshore work.

Talking with the sailmakers who have been open and honest with (rather than trying to sell me a sail or a system), mainsail furlers give up a lot of performance over a normal sail. If I remember correctly, the PHRF analysis concluded that depending on the sail options and the design of the boat, the performance difference was roughly 12 to 30 seconds a mile. Those are very big differences. Accoring to the PHRF report, the difference can be far greater in light air, where the greater turbulence and drag of the oversized mast, and the poorer sail shape (cut flat to minimize the chance of jambing when furled) can really handicap performance.

Although there is a significant loss in performance in light air, the most serious problem with mainsail furling occurs in prolonged higher winds. In high winds sail shape becomes expecially critical. In heavy winds ideally you are sailing with a comparatively flat sail with minimal twist (leech open) or hook (leech hooked to weather). If you carefully furl the sail, you can end up with a pretty desent initial sail shape for heavy air sailing. But when sailing with partially furled sail for a period of time, the layers of sailcloth slide over each other so that the leech creeps down toward the tack. This puts more sail cloth into the body of the sail and greatly increases leech tension. As a result you end up with a very round and powered up sail with a lot of leech hook. That is the perfect combination for a lot of heeling and drag, with minimal drive. In other words exactly backwards of what you want in heavy air. Sailing that way also really strains the leech area of the sail which is why you see a lot of furling mainsails with stretched out leeches and a lot of leech flutter. According to the sailmakers mainsail furlers greatly shorten the lifespan of a sail. Additionally as the sail creeps down the roll it also bunches up which is one of the predominant causes of jambing in high wind sailing.

Given your planned cruising grounds, my conclusion is that the presense of a furling mainsail would be a deal breaker.

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