Steven Shelikoff wrote in message
...
On Thu, 1 Apr 2004 11:45:50 +0100, "JimB"
Your experiment seems to be flawed if you're trying to look
solely at
lateral force with no fore and aft motion permitted and yet you
get a
lot of for and aft swing.

To prove to myself again that there is a lateral force even
with no fore
and aft movement, I put a string around the bottom end of the
spatula
which would allow it to swing laterally but hold it from being
moved
toward the fan. So, we have a plastic spatula hung by the
little
hanging hole at the top from a hook which allows it to swing in
all
directions like a pendulum but I can firmly control the angle
of the
blade by turning the hook. And there is a string looped around
the
handle just above the blade which I can hold to prevent the
blade from
moving towards the fan so there's no fore and aft motion.

Result: same thing. When it's behind the fan and you turn the
blade so
that it's not perpendicular to the fan, the spatula swings
*only*
laterally since there's a string keeping it from moving toward
the fan.

Nice one Steve. I'll have a go at it, and then try to work out
what else is wrong with my mechanism, though I must admit the
results first time were not easily repeatable. So much depended
on the relative distance fore and aft and left and right from the
fan.

Luckily, in a few weeks I'll get my hands on a real boat and
double check!

JimB