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Off Topics > Downwind faster than the wind

spork
Veteran
Location: Mountain View, CA

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We've discussed a wind powered vehicle that goes directly downwind faster than the wind on this forum - and as I recall, there were plenty of non-believers.

I'm trying to get the Mythbusters to do a segment on this (and prove or disprove it for all). But I don't have anyone on that forum pointing out the reasons it should not work. Anyone willing to have the other side of the debate there?

10-12-2008 Over year old.

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scatbass
Heliman
Location: Hiram, GA

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Pictured/diagrams would help a bit. Downwind meaning - you have a vehicle that is moving the same direction as the wind (ie, the wind is blowing this vehicle in some manner)...and, upon reaching max velocity, the vehicles groundspeed is greater than the groundspeed of the wind.

Hmmmmm...

Mike

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Inspector Fuzz
Veteran
Location: NLA

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What force would allow the pushing wind to overcome the resistance of the wind that the vehicle will encounter once it starts to move faster than the "pushing" wind?

I can see how a wing being pushed downwind could generate a lifting force and pull the vehicle faster down wind.

Have you tested this, outside of theory?

Anyone who has sailed knows you can go faster than the wind on a downwind tack, but directly downwind?

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Boidman (RIP)
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Location: The Home Stretch

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http://forum.mythbustersfanclub.com...ic,12948.0.html

There are two different and interesting videos in the topic. One is of the specifics, the other is on a mild tangent, but still intended to help with adjusting the thought processes.

Those folks run a very tight ship, compared to Mark Ryder's slowly increasing leniency.

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holzback
Veteran
Location: noblesville IN United States

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this would kind of be like a row boat in the river, if the boat is going downstream, does it go faster than the current? i dont think it does.

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Boidman (RIP)
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Location: The Home Stretch

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What about a sailboat in a river?

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holzback
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Location: noblesville IN United States

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i think a sail would make it go faster though.

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TachyonDriver
Key Veteran
Location: Chipping, Lancs, UK

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If directly downwind also involved going downhill, then the vehicle would have the added component of gravity and thus would go faster....I think

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spork
Veteran
Location: Mountain View, CA

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Boidman has the right link. And yes, they are *extremely* rigid about keeping the discussion technical and not personal.

The thread is here: http://forum.mythbustersfanclub.com...ic,12948.0.html

I will be happy to answer all questions there (as I have on this forum in the past).

But basically, yes, it's a vehicle that will go directly downwind, faster than the wind, steady-state, powered only by the wind.

And yes, it is somewhat akin to a sailboat tacking downwind, faster than the wind. If you think about it, you could take two tacks downwind, faster than the wind, to arrive at a destination directly downwind faster than the wind gets to that same destination.

But I really need skeptics, or at least curious minded folks, over there to get this thread over the hump so the Mythbusters decide it's worth doing a segment on.

Thanks.

P.S. as far as going downhill (which this vehicle isn't doing), row boats or sailboats on a river, etc. this topic covers all those areas and more.

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jcrack_corn
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Location: End of Time

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it will not fly. no windspeed.

------------------------------------------------------------------
do it inverted
------------

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drdot
Elite Veteran
Location: So. California, Orange County.

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fwiw..

Is it on a treadmill??

BC

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spork
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Location: Mountain View, CA

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Great - the MENSA club has arrived.

10-13-2008 Over year old.

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spaceman spiff
Key Veteran
Location: Tucson

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Good question.

Can't claim to have figured it out, but have a close look a the pitch of the prop and the direction of rotation tward the end of the first push. It's backwards (if you assume the tail wind is spinning it)

http://www.youtube.com/watch?v=aJpdWHFqHm0

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drdot
Elite Veteran
Location: So. California, Orange County.

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fwiw..
Let's see..Spork wants a discussion that's technical...One that's not personal..Then makes a personal attack at anyone who jests a bit...Taking oneself too seriously is the first step to ruin..

Seriously...This idea has as much merit as the car that runs on water..(No, I don't mean a boat with wheels)...Conservation of energy is a law difficult to break...If the cart were tacking, perhaps..What I couldn't determine from the video was the directon of the wind relative to the track of the vehicle..If it was not direcly astern, perhaps yes..Otherwise, I'm one of you detractors...

John.

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funflyer2006
Senior Heliman
Location: CC, Iowa

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Gonna have to go with drdot on this one.

Quote
Conservation of energy is a law difficult to break...I

I don't think the vehicle could ever travel faster than the wind if it traveling parallel to it.

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Tintin
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Location: Akershus, Norway

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Another skeptic..

If you go straight down wind faster than the wind, you are in fact going straight against the wind. So far it is not possible to use than oncoming wind to produce more energy than what it takes to propell whatever you are using to go against the wind.
If that was possible today we had no need for oil. You would only have to use a small electric engine to start and then the oncoming wind would give you whatever energy you need to continue.

Untill you have constructed something that will produce more energy than it consumes to move or a perpetum mobile I wouldn't spend too much time pondering it...work on the efficiency of wind generators in stead. Newton has so far been correct and numerous good heads have tried to make the perpetum mobile...

Sorry for the negative input

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spork
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Location: Mountain View, CA

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Quote
Seriously...This idea has as much merit as the car that runs on water..

Then why not come over to the other thread and let me explain how it's possible. Or, if you're absolutely certain it can't be done, we can stay right here, and you can accept my $100K bet, and I'll be happy to demonstrate it.

>> Conservation of energy is a law difficult to break...

Agreed. Which is why I would never even attempt to break it.

>> Otherwise, I'm one of you detractors...

Clearly, but you apparently don't want to see it actually demonstrated by the Mythbusters - or you'd have the debate on the fan club site.

>> I don't think the vehicle could ever travel faster than the wind if it traveling parallel to it.

And yet it does. Care to see it proven?

>>
So far it is not possible to use than oncoming wind to produce more energy than what it takes to propell whatever you are using to go against the wind.
<<

So you really don't want to understand how this is done?

>>If that was possible today we had no need for oil.

If you understood what is being claimed you wouldn't make such comments. If you cared to discuss it on the Mythbusters fan club site you'd get all the answers.

>>
Untill you have constructed something that will produce more energy than it consumes to move or a perpetum mobile I wouldn't spend too much time pondering it...
<<

I'm not interested in over-unity machines. That's even more pointless than making a toy cart that uses wind power to go downwind faster than the wind.

>> Newton has so far been correct and numerous good heads have tried to make the perpetum mobile...

And Newton is still correct. If you care to understand this problem you know where to go.

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Aaron29
Elite Veteran
Location: BC, LA

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I'm with Tintin on this one. At least for now.

If you go downwind faster than the wind, you are traveling upwind relative to you. So essentially you're making a machine that travels upwind.

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flyboy0413
Senior Heliman
Location: CT, USA

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Rotor blade tips go faster than the wind during autorotation. Think about that...

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Aaron29
Elite Veteran
Location: BC, LA

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Flyboy, I just did.

Gravity is providing the force.

Take that same heli and put it on the bench with the rotors spinning unpowered and they will slow.

Try again...

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