Ø … has a 3 blade feathering or folding prop on a boat as small… <
I had a 3 blade MAX Prop on a Ericson 30+ (2 cylinder diesel) back in the early 80’s. The boat was in a timeshare lease program here in the PNW. For me the three blade extra expense paid off in two ways. My timeshare customers often needed great brakes (i.e. backing power) and the ability to reverse in a straight line. The second advantage has to do with the many hours PNW cruisers will find themselves motoring in summer. A typical timeshare customer will attempt to cover many miles in their one week trip often pushing against the current. For our current C&C 43, the three blade MAX Prop is all about traction. The heavy displacement can be a handful to stop if the skipper F’s up a landing. I have also pitched the prop to allow our Perkins 4-108 to develop full power/RPMs in case I need to power into big seas or out of a tide rip/whirlpool. (Long story short, I miss-calculated slack water at the BC narrows named “Hole in the wall”. Afterward the Mrs mumbled something about “never do that again with me onboard”. My young son just looked up and said “I’m glad I’m not driving”.) >… According to rumor, PYI told someone that the 2-blade MaxProp can cause some >vibration issues between the tip of the prop blade and the flat on the bottom >of the bustle on some C&C's. << I have also experience with the effect of not enough distance between the prop blade and the hull. The rumor is accurate but comes with great variation based on prop diameter and hull shape. Here is another place where a three blade prop may have an advantage. With three blades a smaller prop diameter can be used to allow more space between the prop tip and the hull preventing water from “balling up” (my term not scientific) between the hull and prop. Martin Calypso 1971 C&C 43 Seattle From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Steve Thomas Sent: Tuesday, October 22, 2013 8:08 AM To: cnc-list@cnc-list.com Subject: Re: Stus-List Folding/feathering Props Sam, The original prop was a Michigan Wheel fixed 2 blade, and there was no remarkable change in vibration either way when the Gori was installed. It might have been better, prop mass is more central to the shaft, but it would take some sort of measurement instrument to tell for certain. I have read, and it makes perfect sense, that all else being equal a 3 blade is less prone to vibration, so that is why I was looking. I don't think that I get appreciable vibration from the prop anyway, and whatever there may be is totally swamped out by the one cylinder diesel. (Yanmar YSB12) I did do a careful engine to prop shaft alignment once, which when wrong will cause vibration problems, and I should do it again sometime in mid to late season when the various hull bending stresses have settled down. It is a task best done on a cool day and when in a very patient frame of mind. I am sure that there must be someone who has done it, but I know of no one who actually has a 3 blade feathering or folding prop on a boat as small as ours. Makes it hard to weigh the advantage of such a costly upgrade. Steve Thomas C&C27 MKIII -----Original Message----- From: CnC-List [mailto:cnc-list-boun...@cnc-list.com]On Behalf Of sam.c.sal...@gmail.com<mailto:sam.c.sal...@gmail.com> Sent: Tuesday, October 22, 2013 1:44 AM To: cnc-list@cnc-list.com<mailto:cnc-list@cnc-list.com> Subject: Re: Stus-List Folding/feathering Props Steve, ...and anyone else - how do you find the 2 blade and vibration? I note you had a concern; was the concern justified or does the 2 blade run OK? Anyone have any experience with 2 blade and 3 blade vibration differences? If anyone is interested, I’ve had a quote back from Max Prop already: Current prop is: 12” x 8” RH 3 Blade Recommendations are: 12” x 10” 2 blade - $1500 12” x 9” 3 blade - $2400 sam :-) C&C 26 Liquorice Ghost Lake Alberta
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