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What do folks think is the best prop for an Atomic 4 in a C&C 27 Mk II?
I'll have the shaft out by tonight (the coupling is moving nicely - yay! - but I need a few more washers to get the throw on the bolts), so now I'm thinking about whether to replace the apparently original 1973 right hand 2-blade 11-7 prop with one that is more efficient.
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1974 C&C 27 Mk II in PEI
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1974 Mark II C&C 27
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We all have a tendency to justify our decisions but I can honestly say I'm extremely happy with my Indigo 10x7.4 fixed three-blader designed specifically for the A-4. You might want to check out the "propellor" section in "Black Arts", but I chose the Indigo at the suggestion of a friend who has a Mark III. Propwalk from the original two-blader was horrendous; it's now negligible and the boat stops dead in its tracks when I put her in reverse. You can find the prop at Indigo Electronics; I paid for mine by Visa and had it within a week. Designer has been extremely helpful and I've since purchased several of his A-4 add-ons. Good luck.
Ken Pole, Ottawa
1975 Mark III Santiva
Ken Pole, Ottawa
1975 Mark III Santiva
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Thanks Ken. How about drag while sailing? Before I posted I went all through Black Arts and searched every archived post, as well as discussions wiith sailors here and away -- not an easy decision. The choices seem to be:
1. Original 2-bladed RH 11x7.
2. A folding prop - David W likes the 12x7 Flexofold.
3. A feathering prop - A friend likes the Darglow Engineering Featherstream prop on his larger cruiser (they also sell the Felxfold). On his boat there is some propwalk, but I don't mind a little of that in a sailboat, just a matter of knowing its there and then working with it.
4. 3-bladed prop.
5. Different 2-bladed prop with better efficiencies than the original one.
The criteria to consider appear to be:
1. Improved reverse thrust.
2. Reduced propwalk in reverse.
3. Minimize drag sailing.
4. Efficient forward thrust/RPM/fuel consumption/hull speed combination.
ie, some physics, some magic.
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1974 C&C 27 Mk II in PEI
Last edited by (2008-06-26 20:17:12)
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1974 Mark II C&C 27
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Since my only prior experience was with the factory two-blader, I can only say that I haven't noticed an appreciable difference, including when accelerating out of a tack. Hydrodynamically, there's certain to be a loss when compared with a folder or featherer <img src="emoticons/icon_question.gif"> but those are obviously more expensive and have their own issues, such as weeds, etc. If I was a racer (I prefer to do that on other folks' boats), I'd probably go Gori or somesuch.
Ken Pole, Ottawa
1975 Mark III Santiva
Ken Pole, Ottawa
1975 Mark III Santiva
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I've been thinking of replacing my prop as well (I have the OEM 2 blade). I found this on the web. Has anyone heard of this prop: http://mysite.verizon.net/resqp86c/performancepropellers/id21.html
Greg Tokarz, Nepenthe, Mk1 Hull #73
Greg Tokarz,
Nepenthe, C&C 27 Mk1, Hull #73
National Yacht Club, Toronto
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Our friends on Kat's Paw I have a Gori and they hate it. Scads of prop walk without any noticeable ability to reverse. I had a look at the web site and they look no different from the props I remember from 25 years ago - which means they're the same PITA props KP has. Their geared blades were a revelation a quarter century ago, but the world has passed them by.
David Weatherston
Towser, Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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A wee clarification: I have an Indigo, not a Gori. Have friends who race with a Gori and do really well. Mind you, I've seen them practically lick their bottom (the boat's, that is!) between races.
Ken Pole, Ottawa
1975 Mark III Santiva
Ken Pole, Ottawa
1975 Mark III Santiva
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Bad info in my previous posting. The other 27 sports a Flex-O-Fold, not a Gori. Apologies.
Ken Pole, Ottawa
1975 Mark III Santiva
Ken Pole, Ottawa
1975 Mark III Santiva
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Ken,
Your Indigo is recorded on the Props page and it was clear that you were referring to someone else's prop, so no clarification about Santiva is necessary.
But to get back to the issue of prop choice -- Racing success is not really the subject at hand (though it has to be said that any geared prop is less than the ultimate choice, as they have a larger cross-section than pre-gearing Martecs and Michigans). Nor have we really delved into the issue of performance ahead, except inasmuch as there are a variety of opinions about the correct diameter and pitch for any given make; doing a full analysis of performance ahead for different makes, including issues like fuel consumption or other measures of prop efficiency, would really stretch our interest level (we are, after all, sailors).
Where choice really seems to come in to play for most of us are the related issues of prop-walk and reverse thrust, those two intertwined forces that make us look like masters or victims of the art of docking and undocking. I've listened to a litany of complaints about the Gori previously mentioned. On the other hand, I've been favourably impressed by my Flexofold's behaviour ahead and astern (one of the club's riggers recently commented that Towser manoeuvres like a tugboat, which seems to have been meant as a compliment). It's probably not as good performance under power as could be achieved with a solid prop, but sailboats with solid props always feel a bit unbalanced under sail to me, and sail, after all, is what we're here for.
David Weatherston
Towser, Toronto
C&C 27 Mk IV
Last edited by (2008-06-30 02:21:49)
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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