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Subject: Re: Wind & Current Navigation
From: Herbert Prinz (hprinz@XXX.XXX)
Date: Thu Apr 17 2003 - 03:29:55 EDT
Hello Allen,
You wrote:
> The formula would look something like:
>
> B = s * W + h * C
>
It all depends on the boat. With a full keel, current is more important
than wind. At any rate, this formula would hold for one point of the boat
only: its pivot point. On my full keel cutter, the effect of the current
results in a translation of the boat more or less parallel to itself
(however, see below), wheras the wind causes a rotation, because the wind
force and keel resistance don't act on the same vertical axes.
(Particularly so, as my staysail remains on the boom and the Genoa in a bag
hooked to the forestay.) Add to this prop walk and prop wash and it allmost
does not matter whether I, my wife, or nobody is at the wheel. It is
anybody's guess where this boat is going.
Here in Connecticut it is quite common to find marinas in the narrow rivers
that flow into the Sound. Currents can be several knots. As long as you are
in the slip you don't notice the current that much because it is not so
strong near the shores and it is hemmed by all the keels of the boats in
the finger slips perpendicular to it. As you pull ot backwards and expose
your stern to the full current, it catches you and starts turning you. When
you try to countersteer, hoping to keep the boat parallel to the slip, you
make things worse: The pivot point is normally far aft so that you would
turn the bow downstream instead of the stern upstream.
The solution is: not to try to beat the current (meaning leaving the slip
whichever way the boat wants too, turning around afterwards, if necessary)
and minimizing the time the whole manover takes (meaning full throttle).
Herbert Prinz
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