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  Topic Review (Newest First)
15 Hours Ago 11:01 AM
bobperry
Re: Production Boats and the Limits

I totally agree that some prop walk can help IN SOME docking or tight maneuvers.

But I think I'd rather have no prop walk. On the P'winkle with a sail drive pretty much as far from the big outboard rudder as possible I had pretty much no prop walk that I ever noticed. But I could spin that boat on a dime and it backed like a champ and went where I pointed it. That was very comforting. I'd go with that any day over prop walk. For every time that prop walk can help you there is a time when prop walk fights you. I never needed any help from prop walk on the P'winkle.

FRANCIS LEE is the same way and Kim loves to show off the maneuverability around the dock. With a big spade rudder FL is certainly NOT a powerboat and does not need prop walk for any assist. It's exactly the same with ICON. Prop well forward and big spade rudder well aft. The boat is a pussycat to maneuver and certainly not ever a "powerboat" with dinky little low aspect ratio rudders. Same with ELYSIUM the modified Andrews 70 I did. It's a pussycat under power and maneuvers like a champ with no prop walk. I like the comfort of not having to deal with prop walk and I can assure you that many of my traditional shaft installation boats have had prop walk and some too much.
15 Hours Ago 10:39 AM
Jeff_H
Re: Production Boats and the Limits

I rarely disagree with Bob, but I have to say that I am on the 'prop-walk, and prop thrust against the rudder camp is a good thing' in this discussion. To me prop-walk, and prop thrust against the rudder can be a very useful in slow speed maneuvering, even if it is less efficient than an outdrive when motoring. With the rudder hard over, using back and fill, I can spin my boat in a circle to starboard in a space with a diameter just a half a dozen feet longer than her length.

I had a similar experience with getting on the helm of a boat with a saildrive for the first time in years that was similar to Paulo's story. Last year, I ended up as the helmsman for the bulk of the Governor's Cup on a Beneteau First 44.7 and I so ended up on the helm when we brought her in.

It was a tight parallel spot on the dock and so before approaching the dock I experimented with trying to maneuver at slow speed. I approached a mooring buoy to use as a gauge of changes in speed and direction. I put the boat in reverse and upped the throttle and while the boat slowed to a stop, it did not change direction. I tried backing and filling a few times before I realized that I only had a small amount of 'spin' in forward from the rudder hard over and that this spin was pretty much the same turning either way. It took me a little while to realize this was a saildrive with a maxprop. I think that you get used to what you know, and I know prop walk. It made for a very nervous docking maneuver; one that made me glad to have 8 crewmates, big fenders, and a quickly placed bow breastline and stern spring, to help make it look perfectly executed.

Jeff
20 Hours Ago 06:11 AM
jerryrlitton
Re: Production Boats and the Limits

Quote:
Originally Posted by PCP View Post
Yes I know
I knew that you know, I just wanted to help Bob out. After all, he just thought you were "guessing".
20 Hours Ago 05:50 AM
PCP
Re: Production Boats and the Limits

Quote:
Originally Posted by jerryrlitton View Post

Yes Paulo, you are correct despite what the experts say. I am sure there are a few more factors however generally the closer the prop wash is to the control surface the more effective the control surface is especially during docking. You can have the rudder so far from the prop wash that unless the boat/rudder is moving relative to the water there will be no lift/thrust from the control surface. Bob mentioned low speed maneuvering and we can only imagine by low speed he meant through the water as opposed to over ground. With low speed through the water there is some control however without any movement through the the water you are SOL as far as rudder effectiveness UNLESS you have some prop wash. Prop wash induces relative flow. There are as in life exceptions. However you are correct.
Yes I know

Many years ago when I was trying to dock the first boat with saildrive (after many years sailing boats with conventional drives) trying using the engine flow on rudder to control the boat (almost with no effect) my neighbor at the marina, a very experienced British cruiser said to me:

"New to saildrives I bet!!!"

I said yes and he give me an advise that had served me well since then: "With a sail drive it is better to maneuver as if you don't have an engine to help."

No use on most saildrives to try to use engine rudder effect even if a propeller with a considerable prope walk, well used, can be a big help,I mean in what regards using the engine.
20 Hours Ago 05:30 AM
PCP
Re: Production Boats and the Limits

Quote:
Originally Posted by bobperry View Post
Nope Paulo, wrong. Rudder has it's own job. Some of the very best behaving boats under power I know have the the prop a long distance from the rudder. This goes for very slow speed manouvering. Reality. I have proven this over and over with my designs. But don't let me stop you from guessing.
You mean in what regarding Docking manoeuvers?

I guess that's why all motorboats have the rudder far away from the propeller. A sailboat while doing docking maneuvers is just another motorboat.
22 Hours Ago 03:37 AM
chall03
Re: Production Boats and the Limits

Quote:
Originally Posted by outbound View Post
Don't know why anyone goes to sea. :-).
Because......


1 Day Ago 07:24 PM
outbound
Re: Production Boats and the Limits

Thought you have grease fittings and just pump in more grease time to time. Didn't think ships had PSS.
I have PSS. New one needing no burping. Still makes me nervous. Have retainer so shaft can't fall out. Still makes me nervous. Still makes me less nervous than a sail drive. Worry about grounding, electrolysis, splines, greasing and a big hole in the boat with leaks I can't plug with those.
Don't know why anyone goes to sea. :-).
1 Day Ago 10:15 AM
jerryrlitton
Re: Production Boats and the Limits

Quote:
Originally Posted by outbound View Post
M- maybe be wrong but thought if you have a long tube filled with heavy wt. grease and space between tube inside and shaft is small there is no need for stuffing box or PSS.
Eventually the grease will be replaced with water.
1 Day Ago 07:41 AM
outbound
Re: Production Boats and the Limits

M- maybe be wrong but thought if you have a long tube filled with heavy wt. grease and space between tube inside and shaft is small there is no need for stuffing box or PSS.
1 Day Ago 05:09 AM
jerryrlitton
Re: Production Boats and the Limits

Quote:
Originally Posted by PCP View Post
I guess you are talking about a completely different thing. Jeff was not talking about a behaved boat under power in any direction but about docking maneuvers and in what regards that a propeller near the rudder is an added help.
Yes Paulo, you are correct despite what the experts say. I am sure there are a few more factors however generally the closer the prop wash is to the control surface the more effective the control surface is especially during docking. You can have the rudder so far from the prop wash that unless the boat/rudder is moving relative to the water there will be no lift/thrust from the control surface. Bob mentioned low speed maneuvering and we can only imagine by low speed he meant through the water as opposed to over ground. With low speed through the water there is some control however without any movement through the the water you are SOL as far as rudder effectiveness UNLESS you have some prop wash. Prop wash induces relative flow. There are as in life exceptions. However you are correct.
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