Re: Fwd: Hawaiian trade wind P14/15 HP race

Kent Crispin (kent@songbird.com)
Sun, 8 Nov 1998 23:22:54 -0800


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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On Thu, Nov 05, 1998 at 06:28:04PM -0500, GSTahoe@aol.com wrote:
> Rich--
>
> With a P-15 in 20 knot winds with attendant chop if you where to race three
> boats, one with a Honda 2, One with a Tohatsu 3.5 and one with a Honda 5 from
> island to island, I'm afraid it would be a dead heat. All three would push
> your P-15 at hull speed.

I don't think this is true in general, is it? The thrust generated by
the motor is a function of the HP, and a larger HP motor will
generate more thrust. On the other hand, the resistance to forward
progress comes from two factors, at least: the resistance of pushing
the hull through the water, and the resistance of pushing the part of
the boat above water through the air. The thrust of the motor must work
against *both* of these factors.

That is, if you have a motor just powerful enough to move you at
hull speed in still air, you will go slower than hull speed with a
head wind. Contrariwise, a weaker motor will still drive you at
hull speed if you have a tail wind adding forward thrust.

kent

-- 
Kent Crispin, PAB Chair			"No reason to get excited",
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