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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.

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On 15 Oct, 08:09, toad wrote:
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.

Well, you went completely silent the last time the presence of a
propellor was pointed out to you. I think it was pretty obvious that
you didn't realize its significance.

But here - yet a-bloody-gain - is what you need to know.

1) There is a downwind force on the windmill.

2) There is a change of wind speed across the disk of the windmill.

3) The shaft power produced by the windmill is the downwind force
times the change in wind speed.

4) The power required to move the windmill disk relative to a fixed
point is the force multiplied by the upwind velocity component of the
disk

4a) So to move the disk directly upwind requires power,

4b) To move the disk downwind produces power (in addition to any shaft
power) and

4c) To move the disk across wind requires no power

5) The shaft power produced by the windmill may be fed into a device
capable of moving the windmill - gears, propellor, paddles, generator
and linear electric motor.

6) If, after efficiency has been taken into account, the shaft power
produced by the windmill is greater than the power needed to move it,
it will move.

6a) So a windmill craft will always be able to go down wind

6b) Will be able to go crosswind if the shaft power equals the
propellor losses and

6c) Will be able to go directly upwind as long as the shaft power
exceeds the propellor losses, the maximum speed attainable upwind
being determined by the size of those losses.

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

Good. Since the energy required to push it into the wind is
proportional to the absolute forward speed of the disk, it can be as
small as you like. To - again bearing in mind inefficiences in the
propulsion system - any available shaft power can produce forward
motion. QED.

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:

Can I assume that you have a rasonable base in fluid dynamics and
Kelvin-Froude actuator disk theory?

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.

You have given insufficient information.

But the important thing to remember is ... IT HAS BEEN DONE. By lots
of people. I've seen one of the vessels capable of doing it myself -
it used to live at Tighnabruiach and is now in the Scottish Maritime
Museum Collection.

Arguing about theoretical possibilities is one thing. Arguing that,
because you don't understand the theory, working machines are mass
delusions is a little bit silly.

Ian

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On 15 Oct, 14:27, (Richard Casady) wrote:

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

Kelvin-Froude actuator disk theory is your friend.

Ian

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On 15 Oct, 14:19, (Richard Casady) wrote:
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.

Nope. How many aircraft do you think are capable of vertical takeoff?

A Boeing 747-400 has a take off weight of 875,000 lbf and a total
thrust of 4 x 63,300 = 253,200 lbf.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

Ian

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On 15 Oct, 15:54, Ian wrote:

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:

Can I assume that you have a rasonable base in fluid dynamics and
Kelvin-Froude actuator disk theory?

No, but I will be able to verify your formulas and check your maths
fine.

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.

You have given insufficient information.

Fine, make you own assumptions - just explain what the are when you
post the maths.

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wrote in message
oups.com...
Umm well we can, water can be made to flow up hill on a slope.

http://www.livescience.com/environment/060329_water_uphill.html

No, it can't. The water is propelled by steam. It's not flowing, it's
boiling.

And steam makes a frictionless cushion so it should be shooting
downhill. There was also another URL which you have conveniently
snipped
from your reply.


"Bill" wrote:
And water vapor goes up to make clouds all without the help of scientists
or
steam.


Nice backpedal.
You really urped on that one "Bill."

Please explain. I don't understand your comment.




Gravity does not exist at the LaGrangian point.


Yes it does. Gravity always exists. At a LaGrange point, the gravity
of one mass is cancelled by the mass of another. So gravity has no
effect on free bodies at a LaGrange point, but gravity still exists.

How does one know it exists there? By measuring it? Or by postulating it?
If gravity of one mass is cancelled by another then it does not exist, the
net force is zero. Zero means nothing. Anyway, you are completely wrong.
Gravity can be higher at a Lagrangian point provided it is countered by
acceleration forces. It says so on this NASA website:

http://www-spof.gsfc.nasa.gov/Education/wlagran.html

"There exists another Lagrangian point L2 at about the same distance from
Earth but on the night side, away from the Sun. A spacecraft placed there is
more distant from the Sun and therefore should orbit it more slowly than the
Earth; but the extra pull of the Earth adds up to the Sun's pull, and this
allows the spacecraft to move faster and keep up with the Earth. "

Here we see no cancellation of gravity at all. Your definition of a
Langrangian point is incorrect. There are many places in space where there
is no local gravity.






Oil droplets could go up or down under the control of Milliken.


Wrong again. Oil droplets could appear to go up or down under his
telekinetic control.
"Seems" is not the same as "is" no matter how much it appears to be.


Milliken won the Nobel Prize for measuring the charge to mass ratio of
electrons. He used an electric field to lift or drop oil droplets.
"Telekinetic control" is in the realm of pseudoscience. Milliken was not a
stage actor who entertained audiences, he was a real scientist who
discovered some of the fundamentals we use today. Here is some information
on the man and the experiment:

http://en.wikipedia.org/wiki/Oil-drop_experiment

I may be missing something, but could you refer me to where he used
"Telekinetic control" on the oil droplets. There is some controversy over
his fudging of the data which would indicate he could not use his mind to
control the outcome of the experiment. Could you explain more please?




If one accelerates toward the earth at the correct rate the gravitational
field disappears.


Nope. It is cancelled out by the acceleration (the "correct rate"
happens to be 32 ft/sec/sec, or about 1 g.... how difficult is it to
figure this out?) but gravity never "disappears."

Gravitational field disappears to the observer. The correct rate depends on
altitude and location over the earth. See:
http://en.wikipedia.org/wiki/Gravity_anomaly

http://www.bun.kyoto-u.ac.jp/~suchii/free-fall.html Quotes Einstein as
follows:

"Just as is the case with the electric field produced by electromagnetic
induction, the gravitational field has similarly only a relative existence.
For if one considers an observer in free fall, e.g. from the roof of a
house, there exists for him during his fall no gravitational field---at
least in his immediate vicinity. (A. Einstein, manuscript written in 1919"





Photons do not change speed due to acceleration in the earth's
gravitational
field. They change colour.


An energy effect nontheless. Does a net change in energy always cause
a change in velocity and only a change in velocity? There are other
forms of energy.

Actually it causes a net change in momentum which is a change in velocity or
mass or one looks at the total differential. Furthermore a change in color
is a change in velocity, the photon vibrates about its central position
faster or slower according to its new frequency. If it maintains the same
amplitude and a higher frequency it must oscillate faster. Where do you
think the higher energies come from at higher frequencies (shorter
wavelengths)? Since the ensemble velocity is fixed and the mass is fixed
then the velocity of oscillation must increase to account for the higher
energy.

Velocity is the only form of energy. Heat is the movement of particles,
electromagnetic energy is the movement of charge, etc. Potential energy
(energy not realized) is the only form not involving velocity because it is
static. Furthermore, the velocity must be relative to a reference.






A clock runs at two different rates for two observers travelling at
different speeds.


No they don't. They run at different rates relative to the observers.

I'm talking about a single clock. Why are you talking about 2 clocks? All
measurement is relational.



In other words, "Bill" you flunked the physics test and you don't know
as much as you think you do.

By your standard? Please correct my responses to your comments above.




In spite of all these wonders there still ain't no such thing as a free
lunch.

Got that one right.... the 1/2 pt extra credit doesn't save your grade
though.


I look forward to your help and comments with my replies to your
scientifically astute and accurate commentary. It's not often we get someone
here who really knows their **** and is willing to help others. Thanks
immensely.

Bill




DSK

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"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

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"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)

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"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.

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"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.