On 15 Oct, 07:09, toad wrote:

Intuitively it does seem obvious. As do all the best perpetual motion
machines. It's only when you think about it that the flaws become
apparent and you start to look around to look for the figures. ...and
there are none. The last time this came up we had a 300 post argument
fest and still nobody was able prove it worked.

Toad, my dear fellow, please don't make an arse of yourself over this
yet again. Windmill powered sailing boats which can go directly upwind
have been built many times. Details have been given here - have you
been to see the one in the Scottish Maritime Museum yet?

As I recall, your main failure to understand came from thinking that
there was only a windmill involved, so it case you have forgotten,
please remember that all these designs use a PROPELLOR IN THE WATER
COUPLED TO THE WINDMILL.

Ian