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  #21  
Old 11-04-2010
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Quote:
Originally Posted by bljones View Post
Of course, to be truly awestruck by it's speed, we are all assuming that the surface is level, and that the vehicle is not actually hurtling down a 20% grade.
NALSA requires less than 3.3 ft vertical variation along the track. But the El Mirage dry lake bed is far below this.

Last edited by eyytee; 11-04-2010 at 07:13 PM.
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  #22  
Old 11-05-2010
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First problem I see: In the video, if the wind is behind him, the prop is turning the wrong way. Look at it closely.

Second problem: You're talking about perpetual motion here. Ain't happening, folks. If he can get more output than input, i.e. traveling faster than the wind down wind, then all of the world's energy problems are solved.

It's a scam.
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  #23  
Old 11-05-2010
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Quote:
Originally Posted by LarryandSusanMacDonald View Post
First problem I see: In the video, if the wind is behind him, the prop is turning the wrong way.
What is wrong about it? It turns opposite to the torque generated by the fluid, like every propeller. Otherwise it would be a turbine.

Quote:
Originally Posted by LarryandSusanMacDonald View Post
Second problem: You're talking about perpetual motion here.
Who (besides you) is talking about perpetual motion here? It's just a wind powered vehicle.

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Originally Posted by LarryandSusanMacDonald View Post
It's a scam.
Very unlikely. Why would the North American Land Sailing Association perpetrate such a scam?
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  #24  
Old 11-05-2010
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eyytee:

#1)



The beginning of the video in question clearly shows that the propeller (turbine) blade is going in the opposite direction from what it would be going if the wind were from behind. (A Long, Strange Trip Downwind Faster Than the Wind | Autopia | Wired.com)

If the prop is turning like an airplane prop - (that is powered by the vehicle) then that is indeed the way it would be turning.

#2) I was not the first to mention 'perpetual motion' regarding this. It is mentioned in the Wikipedia. And I maintain, unless the laws of physics are suspended - which happens rarely in our particular realm - you can not go faster directly in the direction of the fluid which is propelling you. Toss your boat in the water and hook up a prop to a paddle wheel - or vice-versa and see how fast you can move up-stream.

#3) Maybe the North American Land Sailing Association is also confused.
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  #25  
Old 11-05-2010
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Quote:
Originally Posted by LarryandSusanMacDonald View Post
The beginning of the video in question clearly shows that the propeller (turbine) blade is going in the opposite direction from what it would be going if the wind were from behind.
No, it just rotates opposite direction from what it would be rotating if it was a turbine.
Quote:
Originally Posted by LarryandSusanMacDonald View Post
I was not the first to mention 'perpetual motion' regarding this. It is mentioned in the Wikipedia.
And what exactly does Wikipedia say about your claim that this must be 'perpetual motion'? Let me check:
Sailing faster than the wind - Wikipedia, the free encyclopedia
Quote:
The wind-powered cart referred to above therefore would not necessarily violate the laws of conservation of energy, nor is it a perpetual motion machine, as it harnesses its energy from the kinetic energy contained in the wind. (...) The cart is an example of a device that, while respecting the laws of physics, appears at first sight to be in perpetual motion: a so-called apparent perpetual motion machine.
Also: lots of references there to mathematical proof that it doesn't violate any laws:
http://orbit.dtu.dk/getResource?reco...=2&versionId=1
http://www.boatdesign.net/forums/att...-wind-ddwe.pdf
http://www.boatdesign.net/forums/att...-wind-ddw2.pdf

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#3) Maybe the North American Land Sailing Association is also confused.
Nope, it's just you.
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  #26  
Old 11-05-2010
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I remain unconvinced. Any referees in the crowd - or are we evenly divided between the skeptics and the believers?
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  #27  
Old 11-05-2010
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Quote:
Originally Posted by LarryandSusanMacDonald View Post
I remain unconvinced. Any referees in the crowd
Don't ask for authority. Think for yourself!
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  #28  
Old 11-05-2010
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Quote:
Originally Posted by LarryandSusanMacDonald View Post
I remain unconvinced. Any referees in the crowd - or are we evenly divided between the skeptics and the believers?
Larry,

Spend some time researching this before you put your foot in your mouth. I have been following this closely for three years and can assure you, it is not a hoax. These guys had big money sponsors and started with a small scale model on SA back in November 2008. For two+ years folks told them they were crazy and now they are all eating crow and we don't hear much from the loud-mouthed doubters anymore... Many folks who's title end in "cist" as in aerodynamicist or physicist etc. have also eaten crow and come to terms with the fact that they were proven wrong on DDWFTTW..

Even Sail Magazine weighed in:

Running Faster than the Wind

This article in Wired is pretty good too:
A Long, Strange Trip Downwind Faster Than the Wind | Autopia | Wired.com

And this is very entertaining thread on SA with 3799 posts and 152 pages long. It lasted nearly three years and finally came to a screeching halt this past July when those who were doubters realized they had been proven wrong:

DDW Faster than the wind and the MythBusters - Sailing Anarchy Forums

You can always feel free to go toe to toe with John, Rick or San Jose State University Aeronautics Department on why this "doesn't work". Unfortunately it will be a blood bath and you'll lose cause it ALREADY BEEN DONE.

BTW Rick and JB (ThinAirDesigns and Spork) answer posts and questions over on SA...
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Last edited by Maine Sail; 11-05-2010 at 02:29 PM.
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  #29  
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It just occurred to me that if you can build this (and I believe it is real), you should be able to build a vehicle that can sail directly upwind using similar principles. Has anyone done that yet?
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  #30  
Old 11-05-2010
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Maine Sail,
Thanks for the warning - I'm used to the taste of shoe leather, and have, more than once, had my foot in my mouth clear up to my knee. I have read what I can find (I tend to skip over the calculus stuff) but remain skeptical.

You said:
Quote:
Many folks who's title end in "cist" as in aerodynamicist or physicist etc. have also eaten crow and come to terms with the fact that they were proven wrong on DDWFTTW..
Could you point me in the direction of some of these 'cists.'

Bear in mind that a decade or two ago 'room temperature cold fusion' was all the rage in the scientific community. But nobody could duplicate it.

Thousands have seen David Copperfield fly, disappear, make the statue of Liberty disappear. Some believe. I remain skeptical.

If there is indeed big money involved, give us a commercial working device. It seems to me it defies the laws of conservation of mass and energy.

It sounds to me that with one of these devices strapped to your back, you could, theoretically, jump out of an airplane (oh, all right, a blimp, or hot air balloon) and fly back to it. You first. I can't cause my foot is stuck.
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