NORDHAVN Rewrites Physics Textbooks
 

On 14 Oct, 17:18, "Bill" wrote:

Read this about lift:

http://home.hccnet.nl/m.holst/LiftDrag.html

Particularly the part about "by definition lift does NOT do work".

What force do you think does work against gravity to allow aeroplanes
to ascend?

Ian

NORDHAVN Rewrites Physics Textbooks
 

On 14 Oct, 23:07, (Steve Firth) wrote:

If you're not moving how can the wind be on your nose?

Motoring?

What you wrote before was "If one is motoring in a calm on a flat
millpond then there is an
apparent wind equal to the speed of the boat from dead ahead."

You then seemed to claim that by changing course this apparent wind
could be made to do useful work.

Ian

NORDHAVN Rewrites Physics Textbooks
 

On 14 Oct, 19:14, (Steve Firth) wrote:
toad wrote:
How does the windmill know the wind is not true wind? It has no
concept of 'true' wind, it lives exclusively in apparent wind.

Most amusing that you call me a troll for pointing out that this also
applies to motor sailers.

But you seem to be claiming that a sail can produce forward force from
a headwind. It's obvious how a windmill might do that, but a
sail ... ?

Ian

NORDHAVN Rewrites Physics Textbooks
 

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

NORDHAVN Rewrites Physics Textbooks
 

On 15 Oct, 07:41, Ian wrote:

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.

Errr, no. My failure to understand is I don't know how much energy a
windmill can harness, and I don't know how much energy is required to
push a windmill into the wind. What mechanism turns that energy into
forward motion is irrelevant. If the surplus energy is there it can be
used to drive the boat with any mechanism you choose.

If the energy a windmill can harness is greater than the energy
required to push it onto the wind it must go forward.

Claiming I don't understand is rather futile. Of course, _I_ don't
understand. The point is you claim you do. So post the figures that
you base your understanding on and then I will share the same
understanding and this issue will be put to bed for good:

20kts of wind on the nose. Assume no friction or drag anywhere in the
system apart from the push backwards on the windmill. How fast does it
go. Show your workings.

NORDHAVN Rewrites Physics Textbooks
 

"Corryvreckan" wrote in message
.uk...
"Andy Champ" wrote in message
news:j-idnSDiMoeUio_anZ2dnUVZ8q-
An apparent wind from dead ahead can add nothing but a force directly
astern.

The case where a true wind from ahead can be used to drive a windmill
that can drive a propeller to propel the vessel is different

I have such a vessel you can buy, she's called "Bhaskara's Wheel".

There is also another option, see he

NORDHAVN Rewrites Physics Textbooks
 

On Sun, 14 Oct 2007 20:37:22 -0700, Stephen Trapani
wrote:

The advertisement never claimed to impart forward force going directly
into the wind. All they claimed was that they could somehow decrease the
load on the motor or increase the efficiency of the system.

Those two sentences mean the same thing. Raising a sail when headed
directly into the wind will increase the aerodynamic drag acting on
the boat, and reduce speed.

Casady

NORDHAVN Rewrites Physics Textbooks
 

On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote:

What force do you think does work against gravity to allow aeroplanes
to ascend?

Thrust from the engine, of course.

Casady

NORDHAVN Rewrites Physics Textbooks
 

On Mon, 15 Oct 2007 00:09:08 -0700, toad
wrote:

20kts of wind on the nose. Assume no friction or drag anywhere in the
system apart from the push backwards on the windmill. How fast does it
go. Show your workings.

If it is unobvious that a windmill can power a prop and proceed upwind
consider something similar on land, with a rack and the pinion on the
machine. They do make gear driven railroads, there is one at Pike's
Peak.

Why wouldn't it accellerate indefinitely with no friction anywhere in
the system. In real life, of course, props are not very efficient.

Casady

NORDHAVN Rewrites Physics Textbooks
 

Richard Casady wrote:
On Sun, 14 Oct 2007 20:37:22 -0700, Stephen Trapani
wrote:

The advertisement never claimed to impart forward force going directly
into the wind. All they claimed was that they could somehow decrease the
load on the motor or increase the efficiency of the system.

Those two sentences mean the same thing. Raising a sail when headed
directly into the wind will increase the aerodynamic drag acting on
the boat, and reduce speed.

Putting wings on a plane increases aerodynamic drag acting on the plane,
yet it increases the speed, right?

Stephen