On 15 Oct, 05:33, "John Smith" x@y wrote:
"Bill" wrote in message

...







"toad" wrote in message
roups.com...
On 14 Oct, 16:52, Andy Champ wrote:
toad wrote:
Care to explain why a windmill which is capable of powering itself
forward against it's own drag can only do it with a true wind? How
does it know if the wind it is 'feeling' is true or not, it has no
concept of true wind which is merely the wind speed and direction at
an arbitary stationary point.

There will be a level of gearing low enough somewhere, so that the
boat can wind itself forward against the winch.
Even so, if the true wind is zero you get no excess of power whatever
you do.

How does the windmill know the wind is not true wind? It has no
concept of 'true' wind, it lives exclusively in apparent wind.

Assume the windmill direct into wind concept works:

You can take your windmill cart, put it on another cart and tow it at
20kts. It sees 20kts and will move forwards along its cart. If you
stop the cart and blow 20kts at the windmill cart it will move
forwards at exactly the same speed.

In other words there is some spare energy left over to drive the cart
forwards after the energy required to hold the windmill in equilibrium
with the wind is expended. In my example above that spare energy is
used to drive the cart forwards but in your example of the windmill on
the foredeck that surplus energy can be used to save petrol.

Now we both accept that idea is laughable so you have to explain why
it's not laughable when the wind blowing is caused by nature.

...but most importantly, why oh why oh why doesn't someone just post
the mathmatical proof, the last time this came up I said I'd leave the
thread 'till proof turned up and none did. Odd that.

http://www.boatdesign.net/forums/showthread.php?t=14182

Reality beats proof.

I'm surprised that the fact that this (windmill boat sailing directly
upwind) is viable isn't intuitively obvious to more people.

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.

As for reality beats proof. FFS. There was a photo of a perpetual
motion machine in the daily mail a few weeks back.