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Old 17-07-2015, 15:16   #31
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Re: Pull to port under power

Moreorless,
Thanks for sharing your experience, I will look at the rudder next haul out. I did however, talk to the designer of this boat and he basically said that sometimes with a spade rudder it's a trade off. He said that you can motor with a pull to port of you can sail with a weather helm but it is sometimes difficult to have it perfect both ways given the geometry of the hull, shaft angle, distance to prop, rudder configuration etc. I can certainly see how complicated it must be. He also said that the same model with the saildrive option didn't exhibit the same characteristics. If this is the case, I would say on this model, the prop walk is probably attributed to the downward shaft angle because the saildrive would be almost straight, horizontal thrust instead of an angular thrust.

Cheers,
Tom

P.S. Good discussions!
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Old 18-07-2015, 08:48   #32
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Re: Pull to port under power

Sounds like the prop is mounted "centreline" which looks nice. But to counteract the propwalk on a fin keel racer, the prop is often mounted off centre, so the boat goes straight in forward.

On the early C&C27 (very popular model around here) this is the difference between the mark 1 and the mark 2. Soon after production on the mark 1 started, the correction was made to the design, and the mark 2 was born.
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Old 18-07-2015, 09:29   #33
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Re: Pull to port under power

Over pitched prop is the cause. Adjustable props need to be tuned to the boat after they are installed. 3 - 5 degree rudder offset is normal if the shaft isn't offset. Clear indication of need to adjust / tune the prop is the black smoke at high rpm. Also check to make sure the proper size propeller was purchased to begin with. Max Prop should be able to confirm this when given your boat and engine data.
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Old 18-07-2015, 15:36   #34
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Re: Pull to port under power

Quote:
Originally Posted by Scrimshaw4 View Post
Over pitched prop is the cause. Adjustable props need to be tuned to the boat after they are installed. 3 - 5 degree rudder offset is normal if the shaft isn't offset. Clear indication of need to adjust / tune the prop is the black smoke at high rpm. Also check to make sure the proper size propeller was purchased to begin with. Max Prop should be able to confirm this when given your boat and engine data.
Scrimshaw,
I think you are thinking the way I am, the over-pitched prop may be contributing a little. It may not stop it, but it may make it less noticeable. On this issue the black smoke is something that definitely needs to be taken care of.

Cheers,
Tom
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