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Old 11-11-2004
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2 blade or 3 blade propeller

A couple minor points, a three blade prop of equal thrust generally will have significantly greater drag than the two blade under sail. In most regions PHRF gives six seconds a mile for a three blade fixed prop vs a two blade fixed and I have talked to owners who convert back to two blades for racing because they claim that they can''t sail to their rating with thier three blade props. Obviously it depends on the boat and the props.

I am also surprised at the big change in pitch. Since you are not changing the transmission, I would expect that the pitch should be roughly the same for both propellors since pitch is theoretically the amount that the boat would advance with one turn of the propellor assuming zero slipage. The slippage should be fairly similar between the two props in flat water and so I would expect the pitch to be much closer.

Jeff
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