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Down wind faster than the wind

Michael C said:
Wind is relative motion between air and ground, in a direction parallel to the ground. It doesn't matter if we consider the ground to be staying still and the air to be moving, or the air to be staying still and the ground to be moving: in both cases there's a wind.
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I think this is still fairly specific. Even in daily conversation I basically use it to mean airflow relative to me (or to some other observer). For instance, I would call the airflow outside the car window wind. And one of them is called the windscreen, so the inventor of said screen appears to agree.
 
H'ethetheth said:
How so?
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Out of curiosity, why are you guys feeding this one? The humber one is at least somewhat entertaining - when you poke it long streams of nearly grammatical nonsense words come out. But this one doesn't even do that.
 
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sol invictus said:
Out of curiosity, why are you guys feeding this one? The humber one is at least somewhat entertaining - when you poke it it produces long streams of nearly grammatical nonsense words. But this one doesn't even do that.
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I'm trying to get him to say something that will indicate there's a human being in there.

...and masochism.
 
sol invictus said:
Out of curiosity, why are you guys feeding this one? The humber one is at least somewhat entertaining - when you poke it long streams of nearly grammatical nonsense words come out. But this one doesn't even do that.
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You still here?
Oh, I forgot. Caesar, admires in mirror.....exits stage left.
 
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Unlikely to be a bot. Just taciturn. The idea of someone publicly disproving another's claim, on a machine with an imaginary wind, is beyond parody.
 
humber said:
The idea of someone publicly disproving another's claim, on a machine with an imaginary wind, is beyond parody.
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And yet the trolls never address the oft repeated following:

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If I simply increased the size of my treadmill enough, I could set you in an easy chair on the porch of a house on a hot summer day and with the treadmill set at 10mph, you would be telling us how sweet the tea was and how nice the breeze was.

The flag on your porch column would stand proud, the wind chimes would be a 'clanging and the shrubs and trees would be swaying -- all because of a treadmill that "can't make wind". And of course you would be arguing strenuously with us that it's REAL wind and would not believe me when I told you that it was all just a treadmill.
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JB
 
ThinAirDesigns said:
And yet the trolls never address the oft repeated following:
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It's not just that they don't address it - it's completely absurd to be arguing over it at all. It's like an argument over witchcraft, or the four humors (actually it's much worse than that - doctors were talking about yellow bile long after Galileo was dead).
 
ThinAirDesigns said:
And yet the trolls never address the oft repeated following:

--------------------
If I simply increased the size of my treadmill enough, I could set you in an easy chair on the porch of a house on a hot summer day and with the treadmill set at 10mph, you would be telling us how sweet the tea was and how nice the breeze was.

The flag on your porch column would stand proud, the wind chimes would be a 'clanging and the shrubs and trees would be swaying -- all because of a treadmill that "can't make wind". And of course you would be arguing strenuously with us that it's REAL wind and would not believe me when I told you that it was all just a treadmill.
--------------------

JB
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Thanks for the allegory, but I think that the "wind" may perhaps only exist just above the treadmill surface, in a sort of laminar flow kind of way.
That it is defended, just makes it funnier.
 
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sol invictus said:
It's not just that they don't address it - it's completely absurd to be arguing over it at all. It's like an argument over witchcraft, or the four humors (actually it's much worse than that - doctors were talking about yellow bile long after Galileo was dead).
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Or a treadmill in a van. That's voodoo science, that is.
 
H'ethetheth said:
I think this is still fairly specific. Even in daily conversation I basically use it to mean airflow relative to me (or to some other observer). For instance, I would call the airflow outside the car window wind. And one of them is called the windscreen, so the inventor of said screen appears to agree.
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Of course we can define wind relative to a moving car, a moving boat, or whatever. The essential point is that wind is air moving relative to something else.

When we're talking about the subtleties of something that goes faster than the "wind", we need to be quite clear about our definitions. One of the barriers to the correct understanding of the DDWFTTW cart is a shifting definition of "wind". We start out seeing the wind relative to the ground, and when it is stated that the cart runs faster than the wind, everybody seems to agree that the two speeds are to be measured relative to the ground. But many people have said that when the cart gets up to the speed of the wind, there's no wind acting on the cart, so the wind can provide no power. They've changed their frame of reference without realising it. Yes, the wind relative to the cart at this point is zero, but it is not the wind relative to the cart that is providing the power. The power is coming from the wind relative to the ground, which hasn't changed.
 
Michael C said:
Of course we can define wind relative to a moving car, a moving boat, or whatever. The essential point is that wind is air moving relative to something else.

When we're talking about the subtleties of something that goes faster than the "wind", we need to be quite clear about our definitions. One of the barriers to the correct understanding of the DDWFTTW cart is a shifting definition of "wind". We start out seeing the wind relative to the ground, and when it is stated that the cart runs faster than the wind, everybody seems to agree that the two speeds are to be measured relative to the ground. But many people have said that when the cart gets up to the speed of the wind, there's no wind acting on the cart, so the wind can provide no power. They've changed their frame of reference without realising it. Yes, the wind relative to the cart at this point is zero, but it is not the wind relative to the cart that is providing the power. The power is coming from the wind relative to the ground, which hasn't changed.
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It seems to me that it may just be easier not to shift references at all.
The problem of faster than wind travel is more than just that. The means of time and measurement would be critical to any claim. The closer the cart gets to windspeed, the more accurate the measurement would need to be.
The precise means by which the cart achieves that goal is important too.
Given free reign, a faster than wind cart is not difficult to build.
 
humber said:
Thanks for the allegory, but I think that the "wind" may perhaps only exist just above the treadmill surface, in a sort of laminar flow kind of way.
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Actually humber, you are precisely wrong. In this sunny porch scenario there is exactly no "wind" just above the treadmill surface, just like in all cases where air moves relative to a surface.

Michael C said:
Of course we can define wind relative to a moving car, a moving boat, or whatever. The essential point is that wind is air moving relative to something else.
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That is exactly what I was getting at. I just thought your previous definition was overly specific.

When we're talking about the subtleties of something that goes faster than the "wind", we need to be quite clear about our definitions.

[...snip...]

They've changed their frame of reference without realising it. Yes, the wind relative to the cart at this point is zero, but it is not the wind relative to the cart that is providing the power. The power is coming from the wind relative to the ground, which hasn't changed.
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I'm sorry if I led you to believe that this particular choir needs preaching to, but you are. :)
 
tsig said:
The wheels spin the prop, the prop moves the cart, the cart spins the wheels.
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Yes. And the velocity difference between the road and the air provides the energy to keep it moving, even when it is moving faster than the wind. Just do the energy calculations and see for yourself. If you can't do the energy calculations you have no basis to argue that the cart can't do what is claimed.

I have not personally seen one of these carts but I have faith in my math and physics that I know it is possible. The energy calculations show that the efficiency of the system needs only to be greater than 50% to maintain its motion at the speed of the wind. The biggest loss is in the efficiency of the propeller and even the Wright Brothers were able to achieve over 60% on their hand made propellers. Modern aircraft propellers are typically over 80% efficient.

I have expressed my faith by offering a wager that independent testing will confirm that a cart can perform as claimed. Do you have similar confidence in your belief?
 
tsig said:
Why do world class sailboats have spinnakers?
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Because with spinnakers they can project more sail area and thereby get more driving force. For conventional boats, the hull drag increases dramatically when aproaching so called "hull speed". At this point any excessive the force is no no longer driving the boat faster but instead only increasing the wave the hull makes going through water. Thats why the world class sailboats need all the force they can get to go just that bit faster and thats why they use spinnakers. And thats also why they never reach windspeed and therefore can keep utilizing the spinnaker, which is useless upwind.

But why DO iceboats NOT have spinnakers? ;)
 
humber said:
The problem of faster than wind travel is more than just that. The means of time and measurement would be critical to any claim. The closer the cart gets to windspeed, the more accurate the measurement would need to be.
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Not really. Only if you are trying to measure how close to actual wind speed the cart gets, not if it can go faster than the wind. Once it exceeds the speed of the wind, a simple visual verification is all that is needed.

That's like saying that if you have a constant speed input and you want to slow down the output to as low a speed as possible, a precise measuring system is needed to determine how close to infinite the gearing is as the output slows - unless the output stops and then reverses direction without disengaging. Then there is no doubt that the ratio reached infinity and is now coming back down on the other side. Do you see how that applies?

humber said:
The precise means by which the cart achieves that goal is important too.
Given free reign, a faster than wind cart is not difficult to build.
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Given the present set of rules, the floor is always open, Humber. I await the physical manifestation of your esoteric cogitations.
 
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