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RE: Hull Speed for san juan 23




Gene, do you know the hull speed for the san juan 23, and is it the same for
the mark I swing keel and the mark II fin keel?  The usual calculation (1.34
X square root of the waterline) would indicate about 6 knots, but I have
seen calculations on the web which put it as high as 7.6 knots.  As well,
some recent literature indicates that the usual formula applied more to full
keel boats, and may be an undercalculation for lighter displacement/flatter
hulled boats.
In my own experience, I recently calibrated my knotmeter based on GPS
readings on absolutely calm/no wave or wind water (using the motor), so I
think it is fairly accurate.  Since then, I have sailed at 6.8 to 7.1 knots
in 15 to 18 knot winds, and once had the knotmeter read 10 knots when on a
run I had two successive larger waves from astern, and felt like I was
surfing down the second one (interesting, unexpected experience in my mark
II fin keel boat!).
I would appreciate any comments you could provide, based on your expertise.
Thanks.
Frank.

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