Propeller position? - Page 2 - SailNet Community
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post #11 of 14 Old 06-29-2008
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how would you know...

absent a folding prop, how can you tell which way the prop is oriented when you shut down the engine...
looked all over my boat for the "align prop vertically" switch, but i can't seem to find it.
really, when it gets down to it, unless you have a prop suitable for racing, i'm thinking one should worry more about a clean slippery hull, and spot on trim, than negligible drag from your prop.
i have an offset 2 blade, sail w/ it in R...not a lot i can do about the effect it has in the water, ergo, i try, (try being the operative word) to focus on eeking out all the speed from sail trim and weight distribution.
anyway...my $.02
great day of sailing on the bay yesterday, worked my new crew hard(i think they'll be back)..now boat projects to finish.
have a great sunday all.

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post #12 of 14 Old 06-30-2008
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Quote:
Originally Posted by sanctuarysam View Post
absent a folding prop, how can you tell which way the prop is oriented when you shut down the engine...
When the boat is on the hard, align the prop vertically, and then mark the prop shaft inside the boat, so that you can see, visually, when it is aligned after you shut off the motor. When my boat is under sail, I can easily turn the shaft by hand to align it.

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...really, when it gets down to it, unless you have a prop suitable for racing, i'm thinking one should worry more about a clean slippery hull, and spot on trim, than negligible drag from your prop.
The fixed 2 blade prop on my boat isn't set in an aperture. It's very similar to the prop and shaft in the above photo of "Figment." I can't prove it, but believe that, if the prop isn't aligned properly, it sometimes causes the boat to point higher on one tack than on the other. Since I have been aligning my prop, it hasn't done that. I suspect that, if the prop is not upright, it creates turbulence over the surface of the rudder that creates an imbalance in the pressures over the rudder's surface. If the prop is upright, it minimizes the imbalance.
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post #13 of 14 Old 06-30-2008
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with an offset prop...

on my boat, i can't seeing it mattering a whole lot...assuming your rig is tensioned properly and balanced, rudder, rudder post and wheel/tiller are also properly aligned, and of course your rudder and keel faired, then maybe there is some measurable drag..i can't, nor really care to try to get upside down in the engine compartment to hand turn the shaft...frankly it's just not practical, and as i don't intend to pull my boat anytime soon (bottom done late nov w/ periodic swim-bys of a diver to check my ablative)..so i think a clean bottom and putting my boat on a diet would affect my boat speed more than 20 degrees off on a prop..
but..we all try to squeeze every bit of boatspeed..if it works for you..hey great.

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post #14 of 14 Old 07-01-2008
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On a long keel ship, mark the propshaft coupling so you will be able to align the prop with the keel. I reckon it makes a difference in lighter airs. It would help a bit in all circumstances though, particularly on a long haul, so it's worth doing.
Often I have got to stop the ship in order to align it. If the ship is moving, the forces are simply too high for my poor wee fingers.
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