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post #16 of Old 03-13-2013
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Re: Modern design + full keel?

Originally Posted by zeuss View Post
My initial thought was that with a full-keel a modern boat could benefit by becoming more stable (hence safer) in blue waters. At this point I didn't know that the impact of the hull design would have that much of an impact on the overall performance of the boat. This relationship is what I was curious about. I now have a better idea as to why. Thanks guys.

I personally like the design of modern boats, but the thought of going to sea (coastal initially) with boats that have been labeled as "unstable" by many as soon as the wind picks up is not really reassuring.
I know this may be an exaggeration from my side, that there are loads of boats with fin keel which are indeed very stable indeed, perhaps I'm being too conservative here? I'm all for safety at sea no matter what.
As I said above, I'm fond of these new boat designs, but I wouldn't go as far as to trade safety for beauty, unless I can do something to get similar performance (stability, safety, etc).

I don't care so much about speed as long as the boat is not one which would force me a fast escape from mid winds.
I respectfully suggest that you are misunderstanding something about fin keels versus full keels. There is absolutely nothing inherently 'unstable' about a fin keel, or inherently more stable about a full keel.

From a design standpoint, a sailboat's need for stability is a relative thing, by which I mean, that stability should be thought of relative to the boat's drag. The more drag a boat has, the more sail area it needs to move, and the more stability that a boat needs to carry that sail area. What ends up happening with high drag vessels (full keel boats that are also short for their weight) is that they tend lack the stability to carry as much sail area as they would ideally have. Work-arounds like a low aspect rig, allow greater sail area, but in doing so end up with lower efficiency sail plans, so much more sail area is required for something approaching but not achieving the same performance.

This combination of high drag hull, lower efficiency rig, and lower stability relative to drag usually results in some mix of decreased performance, more frequent sail changes, greater heel angles for a given relative performance, bigger and harder to handle sails, and/or more motoring time.

Because of that, in a broad general sense, it is much easier to achieve a higher useable stability in a fin keel design than it is in a full keel design. That is why modern boats tend to employ more efficient hull fiorms, keels, rudders and rigs. There may be a case why someone would prefer a full keel, but if it is about greater stability, then it is not because the boat has a full keel, but because of other factors that go way beyond the length of the keel.


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