"Ian" wrote in message
ups.com...
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


Work = force x distance

"Ian" wrote in message
oups.com...
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


The sailboat does go forward doesn't it? (Hint: break down the vectors)

"toad" wrote in message
ups.com...
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.



The guy who built the windmill boat could be a lying crackpot. I have not
seen one with my own eyes so your point is valid.

"Richard Casady" wrote in message
...
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

Things can go to infinity:

http://www.oddparts.com/acsi/motortut.htm

"Caution: If a DC motor suffers a loss of field (if for example, the field
power connections are broken), the DC motor will immediately begin to
accelerate to the top speed which the loading will allow. This can result in
the motor flying apart if the motor is lightly loaded. The possible loss of
field must be accounted for, particularly with shunt wound DC motors. "

Here the back EMF of the motor is redirected into the armature and the
motions speeds up infinitely until it flies apart.

"Wilbur Hubbard" wrote in message
anews.com...

"toad" wrote in message
s.com...
On 14 Oct, 15:16, (Steve Firth) wrote:

Nor in the case of the motorsailer will the apparent wind be from dead
ahead.

Oh yes it will!


If only these ******s could learn to draw a simple vector diagram. They
would soon see there are no other vectors than one from the rear (motor
power) and one from the front (apparent wind drag). Duh!

The vector from the rear will be longer than the one from the front. But
the one from the front will effectively shorten the vector from the rear.
The result is a slower forward speed than if the boat was powering forward
in a vacuum where there would be no vector from the forward (from the
apparent wind, at least.)

Only when there is some wind other than apparent wind can you add any sort
of sideways vector to the diagram. The advert is WRONG! It demonstrates a
common ignorance that many sailor harbour.

Wilbur Hubbard

Best way to look at it!

"Stephen Trapani" wrote in message
...
Ronald Raygun wrote:
Wilbur Hubbard wrote:

"Steve Firth" wrote in message
.. .
Wilbur Hubbard wrote:
Among other things, they claim to be able to create something from
nothing. The advert states, "Even in dead air the apparent wind when
motorsailing generates lift and reduces the amount of engine power
needed to maintain the same speed the engine would produce on its
own."
Huh? Tell me I ain't dreaming . . .
You're not dreaming, they're right and you don't understand physics.

Is there any more help that you need?
I had the utmost confidence that the post would usher forth the Looney
bin, perpetual motion crowd! Welcome, to you, sir. It's good to see a
Brit is the first to insert his foot into his mouth.

Well, perhaps the idea is that when sailing into a "dead" wind, the
sails be set horizontally, so that the lift generated by them is in
the direction which is traditionally associated with "lift", i.e. "up".
Like hydrofoils, these aerofoils would cause the hull to ride a fraction
of an inch higher in the water, reducing water resistance.

Alternatively, the idea might be to back the sails, which would generate
a sideways force on the boat, so that it actually travels with some
leeway. If the leeway angle is big enough, and the drag from all this
doesn't slow down the forwards speed much, the effective speed will be
enhanced by the Pythagoras effect. The helm must be instructed to steer
a few degrees off the intended destination, to compensate for this
beneficial leeway.

Ronald Raygun might be right, if the boat is designed in such a way to
take advantage of these effects. The actual effect proposed by NORDHAVN
will have to be known to know if Wilbur is entirely wrong, but we do know
that Wilbur is partly wrong because NORDHAVN doesn't claim any type of
perpetual motion, just that they can return *some* energy back to the
system to *lessen* the energy needed to propel the boat.

Stephen


There is perpertual motion. I will cite 3 examples, which are irrefutable.

1. Law of inertia. An object in motion tends to stay in motion
(perpertually) unless acted upon by an outside force. That's the law!

2. The electrons spinning around atoms. They have been doing it since the
beginning of time. The stout electron never tires, never wears out, never
slows down he just keeps going and going. What powers the little bugger? If
he required power the universe would have stopped a long time ago. He can
orbit under just about any condition, anytime and anyplace.

3. Electromagnetic waves and photons. Current theory has them going on and
on forever, never slowing down.

Our world is bathed in perpertual motion. One has only to look and think.

Bill

On 15 Oct, 16:20, "Bill" wrote:
"toad" wrote in message

The guy who built the windmill boat could be a lying crackpot. I have not
seen one with my own eyes so your point is valid.

You wouldn't have to lie. Natural wind isn't all in one direction. You
could be steaming ahead in your windmill boat on the components of the
wind that are not directly on the nose and really believe yourself to
be sailing upwind. Pyro actually posted a picture of his cart working
- but in the photo he was blowing downwards on it. He wasn't lying, he
realy did think it was going upwind, he just didn't have a handy head
protractor!

It's also worth noting that some of the windmill craft identified in
the course of this 'debate' as craft that could sail directly into
wind turn out to be incapable of going direct into wind!

It's a futile to debate this in words. We need figures. It will be
resolved one day when somebody who genuinely knows (as opposed to
guessing based on gut feeling and justifying it with wordy posts using
analogies) simply posts the worked formula to prove it one way or the
other.

You only have to look at the Conundrum thread to realize just how much
of a pinch of salt you have to take with armchair physicists on usenet!

Steve Firth wrote:

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. Hoist a
sail and you can make no use of that wind, agreed. However that only
applies if you maintain the same course. Now do what any sensible bloke
would do and adjust your course to make use of the wind as well as the
motor. You now have wind in your sails and you still have an apparent
wind. If you look at the force triangle there is still a component from
the apparent wind.


But since you are creating this apparent wind yourself from your own
forward motion, it will come from dead ahead wherever you go. Changing
course will not bring the apparent wind aft so that you can use it.

Jeannette

"Jeannette" wrote in message
news
Steve Firth wrote:

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. Hoist a
sail and you can make no use of that wind, agreed. However that only
applies if you maintain the same course. Now do what any sensible bloke
would do and adjust your course to make use of the wind as well as the
motor. You now have wind in your sails and you still have an apparent
wind. If you look at the force triangle there is still a component from
the apparent wind.


But since you are creating this apparent wind yourself from your own
forward motion, it will come from dead ahead wherever you go. Changing
course will not bring the apparent wind aft so that you can use it.

Jeannette

Suppose the boat could be trimmed under the waterline so it moved in the
water skewed. Then the apparent wind could come in several degrees off of
the bow. Then would it work?

Bill

"toad" wrote in message
ps.com...
On 15 Oct, 14:27, (Richard Casady) wrote:

Why wouldn't it accellerate indefinitely with no friction anywhere in
the system.

....because as it approaches the speed of light it will require
infinate energy.


My flashlight shoots out photons at the speed of light and it is powered by
a 1 1/2 volt battery. Even better, my flashlight moves away from the photons
at the speed of light with the same 1 1/2 volt battery. When do I need to
change the battery?