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Old 04-25-2012
peterchech peterchech is offline
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Re: shoal draft keel vs regular keel

Quote:
Originally Posted by MC1 View Post
As you're deciding this, also keep in mind that there can be a difference between what the manufacture says the draft is and what it actually is when in use with stores, water, fuel, etc.. On my boat, the manufacture claims 4'10", in actual use it's 5'6".
Granted I don't load up my current boat, but it has a listed draft of 2'11" but when I hauled it out of the water it only had a draft of about 2'4" to the waterline, so I guess this works both ways lol

I think it is pretty apparent that upwind performance is hurt by a shallow keel, but my question is HOW MUCH. Is it a little bit of pointing and VMG lost, like 10%, or is it much more?

Most of these shoal draft keels lack a NACA profile (haha I think even the standard fin keels generally lack this but less so) and are pretty thick, so I wouldn't be surprised if the difference in VMG is pretty high. But nautical engineering seems to be an art as much as a science sometimes...

The other question is, is there any advantage to having weight down low in the keel? Assuming that the righting moment is identical, because the shoal drafter has either more lead or a bulbous bottom (my Hunter 25 has both), is there some advantage to having that lower keel? I know that when a boat is dismasted, its motion changes drastically, is there some kind of similar underwater effect to having a longer or shorter keel?
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