Req'd motor hp

TillyLucy@aol.com
Thu, 23 Sep 1999 22:52:34 EDT


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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In the recent thread on how big a motor to put on a P-19 several folks have
mentioned that one should go to a higher horsepower motor if sailing in an
area where there are high currents. I'm confused by this, isn't a current
just moving water? It seems to me that if the boat is equipped with a motor
that will drive it at hull speed there would be little benefit in using a
bigger, heavier, more expensive one. A hull speed in still water of 5 kts.
will get you five kts. over the bottom. Hull speed against a 3 kt opposing
current will get you 2 kts. over the bottom. How is more horsepower is going
to change that? What makes more sense to me is how motoring against a head
wind, towing something or being heavily laden could benefit from more power.
Thought I'm suspicious that with a propeller pitched so that hull speed (or a
little more) was reached at the peak power of the engine even heavy weight or
head winds wouldn't be an issue. When you see an 5 horse engine pushing a
Zodiac along at 12 or 15 kts, you've got to wonder whether that same prop is
the right one to be pushing a heavy sailboat at 5.5 kts.

Dave Kautz
P-15 #!1632 Tilly Lucy
Palo Alto, CA