Join Date: Sep 2009
Location: Kingston Washington
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Re: Cal 35 MKII with Campbell Sailor
If you want a technical reference Dave Gerr's Propeller Handbook is the best I've come across. As I understand it prop diameter and number of blades are to get enough blade surface area so that your engine can deliver its power without cavitation. In general the largest blade diameter that gives you sufficient blade tip clearance from the hull is the most efficient. If a two blade doesn't give you enough blade area you go to three.
If you're not getting full power RPMs your prop has too much pitch.
Having said all that, my opinion is that the technical analysis assumes that your boat is traveling in flat water. Adding wind and waves to what the engine is pushing against favors more blade area e.g. three blade. BTW I have a Campbell. There's a MIT tank test on prop drag resistance that show it to be a good choice for sailboats.