NORDHAVN Rewrites Physics Textbooks
 

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


Kelvin-Froude actuator disk theory is your friend.


Isn't that valid only in the inertial range?

NORDHAVN Rewrites Physics Textbooks
 

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


If the windmill did work we could put small wind turbines on bicycles and
reduce the pedaling load for cyclists and even increase their speeds into
strong headwinds. Or just cut the field current on their dc powered assist
motors and watch them cruise off into the sunset - perpertually!

NORDHAVN Rewrites Physics Textbooks
 

Steve Firth wrote:


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

You are MOTORING. That means MOVING. You can't motor / move on, say
course 180 degrees in a dead calm and then turn say 40 degrees to port
and expect the resultant relative wind to help your progress because the
relative wind is always directly on your nose.

Yes, the steam would make the water move in many directions but the
point is that it's not RUNNING uphill. It's being propelled uphill.

NORDHAVN Rewrites Physics Textbooks
 

In article ,
(Richard Casady) wrote:

They do make gear driven railroads, there is one at Pike's
Peak.

Yep and I took a ride on a Steam Powered, Gear Driven, Railroad Train
that operates out of Tillamook, Oregon, just two months ago...

Way Cool........

NORDHAVN Rewrites Physics Textbooks
 

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.


"Bill" wrote:
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.

There is a big difference between "does not exist" and "net force =
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:



So, you said gravity doesn't exist, now you say that it not only may
exist but that those who know most about it say it is greater; then
you say that I'm "completely wrong."

Good work.


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.


You're welcome immensely.

DSK

NORDHAVN Rewrites Physics Textbooks
 

On 15 Oct, 17:46, "Bill" wrote:
"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.

If you are saying you flashlight moves at the speed of light relative
to you, I'm impressed. If your flashlight moves at the speed of light
relative to it's own output I'm less impressed!

NORDHAVN Rewrites Physics Textbooks
 

On 15 Oct, 17:56, "Bill" wrote:
"toad" wrote in message

ups.com...





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!

If the windmill did work we could put small wind turbines on bicycles and
reduce the pedaling load for cyclists and even increase their speeds into
strong headwinds.

Forget that, you could put windmills on the bonnets of sports cars,
gear their output to the drive and turn that 100mph headwind into even
more power.

NORDHAVN Rewrites Physics Textbooks
 

On Sun, 14 Oct 2007 11:57:47 -0700, toad
wrote:

On 14 Oct, 19:38, Andy Champ wrote:

Same speed *relative to the the surface it is on*.

Yes, so you accept it has spare energy left over after it has overcome
the drag of the windmill. So the windmill on the foredeck of our power
boat has enough energy to push against the wind pushing back on it. It
also has enough energy left over after this to move it forwards.

Which means you can gear that spare energy to the engine and save some
petrol.

Yet you and I both accept you can't do that.

So there's a paradox.

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.

Lets take this step by step.

Or to put it another way "Lets take this step by step so I can keep
talking rather than posting the maths that I claim is simple to prove
my case."

Do you accept that it is possible for the cart to move directly upwind?

It is essential that we assume that to be the case so you can explain
the paradox exposed by the windmill on powerboat example.

If in a headwind the windmill pushes back harder than it is pushed
then it must do that no matter how that headwind comes about. Which
leaves us with a power boat with a windmill on it's foredeck getting a
net gain in energy from wind that it is creating.

No it gets energy from a reduction of the kinetic energy of the _true_
wind.

NORDHAVN Rewrites Physics Textbooks
 

wrote in message
ups.com...
On 15 Oct, 17:46, "Bill" wrote:
"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.

If you are saying you flashlight moves at the speed of light relative
to you, I'm impressed. If your flashlight moves at the speed of light
relative to it's own output I'm less impressed!


My flashlight is not that impressive. If it gave off enough photons it could
move at the speed of light relative to me.

NORDHAVN Rewrites Physics Textbooks
 

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

But in your example, gravity is still causing you to descend through the
air. Unless converting excess speed to height, you only climb because the
air in which you are flying is rising faster than your sink rate.

Presumably, if a boat's motion is generating apparent wind from dead ahead
and a fully battened sail (I say fully battened because it's a better
aerofoil shape) could be set far enough out to achieve sufficient angle of
attack to produce some lift, then a keel boat "may" go a little quicker.
Would the lift produced be greater than the drag though?

Graham.