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  #1  
Old 08-30-2010
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Prop Walk

I've noticed that some boats have a lot of prop walk and some not so much.

The Catalina 27 and 30 and O'day 27 all had noticeable prop walk in reverse.

The Nonsuch 33 and Bene 51 (do you agree Brad) seem to not have the problem.

I'm thinking that it is mostly due to displacement. The heavier the boat the less likely prop walk is to affect it.

I'm sure the type of prop makes a difference but is is it mostly weight?
Have you every done anything to a boat that made the prop walk significantly better or worse?
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Old 08-30-2010
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Many report that switching from a fixed prop to a Max, for instance, has caused a significant reduction in prop walk.

I think it's mostly a combination of prop type, pitch, & size and the underwater configuration of the boat in question.
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Old 08-30-2010
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Quote:
Originally Posted by Faster View Post
Many report that switching from a fixed prop to a Max, for instance, has caused a significant reduction in prop walk.

I think it's mostly a combination of prop type, pitch, & size and the underwater configuration of the boat in question.

Yup.
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Old 08-31-2010
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I don't think weight has much to do with it - my boat weighs 12 tons and I have a significant prop walk.

I'm not complaining though, I find it kind of useful once you know what to expect.
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Old 08-31-2010
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Quote:
Originally Posted by Faster View Post
Many report that switching from a fixed prop to a Max, for instance, has caused a significant reduction in prop walk.

I think it's mostly a combination of prop type, pitch, & size and the underwater configuration of the boat in question.
It seems that switching props often appears to lessen prop-walk, period. Prop type, pitch, etc. also have an effect, but, I think that a lot of the effect is do with the relative movement of the water caused by the roughness of the prop surface. Nice, shiny, new props push more water in line with the axis of rotation, relative to older, dinged-up, somewhat fouled props. The latter transfer more energy into throwing water off to the sides, tangental to the axis of rotation. It's that resultant force vector, away from the rotational axis, that has the greatest effect on prop-walk (that, and asymmetrical flow against the underside of the boat). You can see this for yourself; if you have some fouling on your prop, even just a little, you've usually experience more prop-walk than with a freshly scrubbed prop. At least, that has always been my experience.

Last edited by SlowButSteady; 08-31-2010 at 12:30 AM.
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Old 08-31-2010
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Quote:
Originally Posted by Omatako View Post
I don't think weight has much to do with it - my boat weighs 12 tons and I have a significant prop walk.

I'm not complaining though, I find it kind of useful once you know what to expect.
A very good point. With a bit of experience, prop-walk can be used to get your boat in and out of spots you normally would never be able to manage. For instance, I have a cross wind slip, and the channel between my dock and the one across from us is a bit less than two boat lengths wide. The wind tends to force the bow of the boat in the wrong direction (to port). Getting my boat to turn the requisite 90 deg (stern to port) while backing at slow speed is often almost impossible without the prop-walk pulling the boat's stern around downwind and forcing the bow to point into the wind. Once I get the boat lined up in the channel I then have to be a bit careful not to apply too much forward throttle, which would cause the forward prop-walk to undo the good that I get out of the reverse prop-walk.

Coming into the slip, I often get the bow just inside of the fingers, with the boat still not quite lined up (i.e., at a bit of an angle to the slip), then give it engine a good burst in reverse. This swings the stern to port, lining the boat up in the slip, with still enough forward momentum to finish gliding in.

And when none of the above works? That's what boathooks are for.
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Old 08-31-2010
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Posiiton of the propellor is also important. Sail drives generate less prop walk. It is due to their position relative to the boat. They are more central. The water pushed sideways nearly at the center pushes the boat to a side but but this affect cannot turn the boat as much as a prop which is located near to the rear end.
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Old 08-31-2010
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Prop walk also depends a lot on how steeply angled the propshaft is. A horizontal propshaft, like that found on a saildrive or outboard, generally develops far less prop walk than an angled one...all other things being equal.
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Old 08-31-2010
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Quote:
Originally Posted by davidpm View Post
Bene 51 (do you agree Brad) seem to not have the problem.
Our Bene 50 doesn't seem to have a lot of prop walk. I don't have a lot of other boats to compare it with, so I'll defer to the your extensive Other Peoples Boats research.

We have a 3 bladed prop, so that might be a factor.

[Edit: Last year when our prop fell off in Vinyard Sound, I noticed no prop walk at all, further verifying that this condition is indeed caused by propellers. BTW, we had very little "shaft walk".]

Regards,
Brad
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Last edited by Bene505; 08-31-2010 at 10:20 AM.
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Old 08-31-2010
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Hello,

My Newport 28 (~7500 lbs) with 2 blade prop had about the same prop walk as my O'day 35 (~12000) with 3 blade prop.

Personally, I *like* prop walk as I feel it gives me the ability to move the boat sideways if I have to.

Barry
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