Down wind faster than the wind?

I've been argueing with a guy about whether or not this is possible. He gives this video as proof:



I've said that the treadmill is poor proof of this, since the treadmill is the power source, not the wind, and all this shows is a very efficient power transmission device - a cart that provides enough thrust from its prop to overcome rolling resistance.

Also, the cart at the beginning has its streamer flag blowing forward, which to me indicates that it is indeed slower than the wind. I've argued that the streamer blows towards the rear cuz when the wind slackens, the kinetic energy stored in the spinning prop allows the drive wheels to power the cart faster than the wind, but only for a brief period of time. Then the cart slows - or the wind picks up speed - the flag blows towards the front of the cart, the cart picks up speed, thus again storing kinetic energy in the spinning prop, and then the wind slackens again, and the cart maintains its speed for a brief period, and the streamer blows to the rear again. Rinse and repeat...

I've argued that the correct way to show this is possible is to put the cart in a controlled environment - like a wind tunnel - where the wind speed can be measured and maintained at a steady state. Then put the cart or rollers that has the capability to measure distance/speed that the wheels are traveling. He is resistant to this.

Any thoughts?

it makes sense if the winds coming from behind the vehicle with a prop the vehicle will move no faster than the wind that's blowing it. i guess the way i look at it is the propeller is just a cut up sail that spins and a sail boat cant go faster than the wind that's blowing it can at?

The thing I've got to ask is:
'Why is the cart at 1:20 on the video not going off the road?'

Is it steered remotely, or pulled by a string?

[edit on 20-11-2008 by Toadmund]

from what i gather there calling it phony. id defiantly have to say its toed behind a bike or something. lol there's no way that thing could go that straight that long on its own

From a sailing standpoint no. Sailing on a close reach or approx. 60 degrees to the wind is one of the fastest points of sail not downwind or running. Then again we don't sail with massive props. attached to our boats.

Perhaps this might help you.

www.sailingusa.info...

www.sailingusa.info...

[edit on 20-11-2008 by jibeho]

[edit on 20-11-2008 by jibeho]

thanks man that actually helped clear thinks up a ton.

Seymour check those links out it really helps you see that you cannot move faster than the wind using the wind.

Oh, I'm most definitely not confused.

He is.

He seems to think that it can go DWFTTW in steady state. He's the one - JB - that built the cart. I've made the point that once the cart reaches wind velocity, there will be zero net movement of air through the prop, and the thrust slackens to nothing.

that man has one him self a one way ticket to the loony bin if he thinks you can travel faster then the wind using the wind. haha and the cart looking thing is just the icing on the cake

Sailing doesn't work as if wind were pushing the boat. It is because the sails create vacuum and the ship is actually pulled by this aerodynamic effect. So, sailing down the wind is slower than sailing at an angle where this effect really takes place.

I believe that it is possible that this can actually result in speed which is faster than wind.

then i guess im the one that belongs in the loony bin. now i can see why there are still ongoing debates about this.

reply to post by neonine


Well I guess a heck of a lot of windsurfers are going to be booking places in the looney bin because it's one of the thrills of sailing on a broad reach.

Imagine a right angle triangle. 20 x 20 on the adjacent and opposite.
hypotenuse of the triangle = 28.284.

The wind comes at 'opposite' = 20 knots.
You sail along the 'adjacent' = 20 knots. This creates your 'headwind' 20 knots.

Result is a total wind 'hypotenuse' of 28.284 knots.

SO..

You bear 'offwind' using this new stronger wind which takes you faster than the original wind speed.

Cool eh?

Oops. in answer to original question. Yes you can for a short time.
This is why when you 'Gybe' you can back wind your sail and end up sorta wet.

[edit on 20-11-2008 by AGENT_T]

thanks for the break down iv never really been good at the whole math this but that still leaves us with the question because the theory that you just explained to me doesn't apply to the propeller car thing because the winds never adjacent to the sail/ propeller

reply to post by neonine


Yeah,You're right,doubt that would work due to friction/drag/turbulence/lack of 'apparent wind'

EDIT.. I'd guess that the vid is fake if it is NOT remote steered.

The wind does not come from EXACTLY the same angle even when you're out at sea,gusts come from varying degrees.

PLUS the torque effect from the propeller alone would make it veer to the opposite side of its rotation.

[edit on 20-11-2008 by AGENT_T]

Here are some guys that can occasionally sail faster than the wind on a tight downwind run.



www.sailingworld.com...

I vsualize the mechanism working like a blade or a prop similar to a boat prop actually using the angle of the blade not just to send a prop wash projecting forward but using that friction to carve through and move forward. Almost like a nut moving forward or backward on the bolt.

Does this make sense?

reply to post by jibeho


yea but he has a sail so is it the sail or the prop doing the work
its like what came first the chicken or the egg.

reply to post by neonine


I've watched the propeller car video a couple of times and it puzzles me.

To effectively travel downwind and maintain speed you have to have the wind precisely at your back. Any deviation in wind direction or error in steering and you lose speed. I don't buy it.

reply to post by jibeho


EXACTLY.. and on a road surrounded by houses/trees/other cars/lamposts???

Can u smell what this 'Crock' is cooking?

i know me nether you have the propeller which is a spinning sail and from what i gather is supposed to have the wind pushing directly at it and then you have the real sail at an angle to the wind to cant the "real wind" which is the only thing getting it to go faster than the winds blowing, that means the propeller is doing nothing but creating drag. its so hard to explain how I'm visualizing this lol

reply to post by neonine


It all gets pretty mind numbing when you start looking at all of the formulas. I'll leave all of that to the mathletes. I just sail as fast as the wind will allow me to.