Charlie;
An earlier post containing a quote from a prop manufacturer who pointed out that, contrary to popular misconception, a 2 blade prop will develop more thrust than a comparable diameter 3 blade prop. That’s because as a prop rotates, each of the blades creates an area of turbulence behind itself that reduces the efficiency of the blade following. The blades of a 3 blade prop, by simple geometry, each run in greater turbulence than the blades of a 2 blade prop. To compensate, the blades of a 3 blade prop are made wider than the blades of a 2 blade prop so they have more surface area producing thrust. I can’t recall for sure, but I don’t think that too small a clearance between the prop tips and the hull will cause cavitation. But I do know from experience that you will get some wicked vibration and noise when the pressure wave that follows the tip hits a hull that is too close to the tip. Rick Brass From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of cenel...@aol.com Sent: Tuesday, January 14, 2014 4:53 PM To: cnc-list@cnc-list.com Subject: Re: Stus-List folding prop for C&C 40 Most 2 bladed props will be larger in diameter than a 3 blade to make up for the lack of surface area in the blades for equivalent thrust.
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