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Re: sailing upwind?



On Fri, 31 Dec 1999, Ludwik Kowalski wrote:

William Beaty wrote:
... suppose we build a machine that contains a pair of sailboats
with sliding connection to a long rod. Orient the rod perpendicular
to the wind, start with the sailboats near each other and at opposite
tacking angles, then let the whole assembly go. When the boats
reach the ends of the rod, they tack again. Each boat never sails
directly into the wind, but the "machine" as a whole does so.

One sliding connection or two sliding connections? Do you suggest
I drill a hole in each boat (from side to side) and insert a rod into it?
How should the sails be oriented?

If the rod is massless, only one sliding connection would be needed! :)
Don't drill holes through the hulls, since that would prevent tacking.
Drill a hole through a deck-mounted swiveling upright cylinder, one for
each boat. I'm imagining two separate sailboats which simultaneously sail
upwind by tacking... but then connect them together somehow with a sliding
horizontal rod and swivel device. The boats would NOT exchange any forces
as long as they sailed approximately abreast, therefor we have not
interfered with the usual physics of a pair of sailboats. The two boats
tack with opposite phase, and so the whole assemblage moves into the wind
with the individual keels tracing a path like this:

/ \
/ \
/ \
\ /
\ /
\ /
\ /
\ /
/ \
/ \
/ \
/ \

To "morph" this into a single simpler device, perhaps we could use just
one sailboat, but lift the boat out of the water at the end of its
diagonal path, then transport it back through the air, so the path looks
like this:

\
\
\
\
\
\
\
\
\
\
\
\

Fasten several boats to the ends of spokes on a huge, rotating wheel, so
that they successively dip into the water? But that would resemble a
multi-blade ships screw (although half of it interacts with air). And if
the sails were addressed separately, that device would resemble a windmill
of sails connected to an underwater propellor. The end result SEEMS
identical in principle to the device with the air-prop connected to a
submerged water-prop via a rotating shaft. This leads me to suspect that
the two-props device WILL move into the wind, and is not a perpetual
motion machine after all, but instead simply employs the physics of
tacking sailboats.

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William J. Beaty SCIENCE HOBBYIST website
billb@eskimo.com http://www.amasci.com
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