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Old 09-01-2013
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Re: Cat 25

Blown out sail are just inefficient at translating wind power to forward motion, particularly when sailing close-hauled. In such a case, hull speed has little to do with it, because the sort of boat we're talking about here has a hard time getting all that close to hull speed on that point of sail unless the water is particularly flat. Usually, when sailing close-hauled, a small displacement boat is slowed by the oncoming waves so much that it can't really accelerate to hull speed before the next wave. It isn't their hull speed that slows them down so much as their lack of forward momentum relative the the waves. When a wave slows the boat the wind tends to cause excessive heel because that's the only thing it can do when the forward motion of the hull is impeded by having to climb a wave face. Good sails simply give the boat the extra power needed to keep moving.

Downwind, or better yet on a broad reach, is a very different story. In that case you can accelerate down the face of the waves in a following sea and stay above hull speed for much of the time.

The bottom line is that to say, "Once at hull speed, any additional power (from more sail area, or greater lift of the existing sail area) will just be wasted..." is just plain wrong. Even at hull speed, added power will result in added speed. Granted, not as much added speed per unit power as one can expect at velocities less than hull speed, but added speed nonetheless.
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