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    Re: Prop-walk.
    From: Rodney Myrvaagnes
    Date: 2003 Apr 23, 00:59 -0500

    On Tue, 22 Apr 2003 20:05:04 +0100, George Huxtable wrote:
    >George rises to the bait-
    >Well, the causes and effects of prop-walk are, I think, often
    >misunderstood, and that could make a fruitful thread.
    >Why does the stern kick sideways? Does yours, like mine, do so much more
    >strongly when the vessel has no way on, or is in reverse, or with the
    >propellor back-pedalling to slow the vessel down, than it does when driving
    >forward? If so, why? Why does it kick in the direction it does? Do
    >single-screw merchant vessels show the same behaviour?
    One data point. Our sailboat, a J36, has the engine amidships and the
    propellor is aboout 12 feet away from the rudder. We get no propwash on
    the rudder, so no steerage unless the boat is moving. But, we also get
    no propwalk.
    To slow the boat going forward, we have to spin the engine pretty fast
    to unfold the Martec prop, but it doesn't move sideways at all. I
    attribute this to lack of torque about a vertical axis, with the prop
    so far forward.
    Rodney Myrvaagnes     NYC                                           J36 Gjo/a
    The sound of a Great Blue Heron's wingbeats going by your head

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