Join Date: Nov 2006
Location: Beacon, New York
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Itís somewhat of an art and not straightforward at all. The shape of the area around the propeller and in fact the shape of the hull will affect the slip of the prop as just one factor. That factor alone makes a great difference and if you have a Westsail 32 the slip is considerably greater then on a Person Flyer for instance. The idea of checking with the Westsail forums is a good one and you might want to start there. You can get enough information to calculate the slip from other boats and use that to enter the formulas to calculate for your own engine. It doesnít matter who made the engine the only thing that matters is the HP, RPMís and propeller pitch and diameter. And the slip is the same for a given hull and all engines/ propeller combinations and only varies by the shape of the hull.
The diameter is clearly related to HP and RPMís so thatís easy to figure out. The pitch is controlled by slip and the shape and number of blades and the RPM of the shaft.
Good luck and all the best,
Study the history of naval architecture and move forward knowing what didnít work before.
Donít waste time making the same old mistakes but instead make new ones and to insure your place in history be sure the mistakes are big ones.
Never design a mast that is weaker then the boat
Never design a boat that is weaker then the mast
Never listen to someone describe why your project will not work unless they can show you the broken pieces of their own version.