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Old 03-31-2009, 12:24 PM
IONA IONA is offline
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Join Date: Mar 2009
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Location: Louisiana
Keel design at prop

She's a 57' George Beuhler designed cruiser and I am nearing the end of building the keel. My engine is a DD4-71 and I have a 2" shaft to a 28-20 3-bladed RH prop. The keel is 11" thick. My question is what is the best way of carving that big thick keel in the area around the cutless bearing housing so as to maximize flow over the prop and minimize the kick of the prop as well. I assume I will want to carve what, viewed from the stern, would look like an "S" shape, with the shaft coming out in the middle of the "S" but my question is, which way will the prop kick the boat? And which way should the "S" face? Should it look like a standard "S" viewing her from the stern, or a reversed "S", and why? If this is not a clear question please view my little attached drawing.


View my progress at this album page:
http://picasaweb.google.com/GreyFox1931/GregSBoatyard#
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Keel design at prop-s-cuts.jpg  
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Old 03-31-2009, 07:18 PM
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PAR PAR is offline
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Again, duplicate post, see the wooden boat section . . .
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Old 04-01-2009, 03:30 AM
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SViau SViau is offline
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Props are designed to work in a uniform steady flow, and creating a non-symetrical flow can bring some surprises, especially considering cavitation.

The most important is to minimize the wake of the hull on the neighborhood of the prop (the part affected by the boundary layer created by the hull).

The best thing to do is to smooth both sides of the keel as much as you can, and avoid the sharp squared trailing edge of the keel
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