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    Re: Wind & Current Navigation
    From: Herbert Prinz
    Date: 2003 Apr 17, 18:20 +0000

    Trevor,
    
    You are right on target with your analysis. I was just about to say the very
    same thing, except that I would give a little more attention to these first
    critical seconds right after releasing the dock lines. Dan's problem is
    trivial in so far as the current comes from dead astern. But in the general
    case an athward current will introduce a rotational forces on the boat until
    the boat reaches the speed of the water. Other than walking out the boat with
    lines, installing a bow thruster, or using as much throttle as possible and
    pray, I would be interested to know what can be done about it.
    
    As I have emphasized in my previous message, and George and you have pointed
    out again, the biggest problem is that the current that prevails one boat
    length away from the slip is likely to be very different from what it was in
    the slip, again, causing the boat to spin.
    
    I also think that it is unnecessary to analyse the problem in terms of
    forces. Course and speed vector diagrams are sufficient because the forces
    cancel out: If the winddrag force increases with the square of the wind
    speed, so does the drag force through the water with boat speed. I looked at
    a diagram in Kotsch and Henderson, "Heavy Weather Guide", 1984, p.282,
    showing leeway of a liferaft versus wind speed. The dependence is almost
    perfectly linear.
    
    Herbert Prinz
    
    "Trevor J. Kenchington" wrote:
    
    > Dan,
    >
    > It may sound silly but think you are asking the wrong questions. [...]
    
    
    

       
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