Rick Cavallaro and his friends have built a wind-powered vehicle that travels downwind faster than the wind, solving a riddle that can start fights.
The unusual wind-powered car hit a top speed 2.86 times faster than the wind during one recent run, a feat that — depending upon your perspective — is either the result of hard work or the same voodoo responsible for Ryan Seacrest’s hair.
The counterintuitive idea that you can travel downwind faster than the wind is casus belli for aerodynamic arguments from internet forums to college classrooms. The concept known as DWFTTW can cause world-renowned physicists to throw their Nobel Prizes in fits of rage.
Someone uses the concept used by the first sailboat and people are arguing about it?
In sailing we call it Air Apparent……it has been known about for a long long time
just put one on my car,
oh shit! (overpass)
It isn’t “Air Apparent” (“apparent wind” in the USA AFAIK) exactly.
The device must travel downwind, by at least some amount, to advance by pushing air back against the apparent wind.
A sailcraft redirects the wind by a small angle to derrive thrust.
@#1 : Standard sailboats go fastest when at the angle to and INTO the wind. Sailboats (until recently) go very inefficiently downwind.
I withdraw my remark. I’ve got to stop
posting while drinking.
Part of what this guy said does not compute. I can understand the wind turning the propeller turning the wheels but if you turn that around you should be coasting to a stop or have another power source than wind.
Ice boats on the Hudson were supposed to have reached speeds of over 100 mph on the Hudson during the 1800s. Going faster than the wind using wind power is not new. It isn’t even last century.
If they can’t explain it they don’t understand it. (The explanation by the builder was pure circular logic; i.e. “it works because the wheels push the propeller and in turn the propeller turns the wheels.”)
I still don’t believe it, in fact. This is a hoax.
Traveling faster than the wind is not the claim. Traveling faster than the wind while going downwind is the claim.
If this is true the only explanation I see is that the propeller is acting as a sail going crosswind.
Go to youtube and search for DWFTTW.
Easy, have the car first stay still while the wind is blowing, then once it starts, it uses the saved energy to move.
They should have used one of the other photos.
On the one shown the orange tape and wind
instrument shows car is slower then the wind
when the picture was taken.
Note , others on the original web site show
the opposite.
Howdy all. I’m the pilot in the pic (and one of the two designers and builders).
>> If they can’t explain it they don’t understand it.
Ah – but we can.
>>
(The explanation by the builder was pure circular logic; i.e. “it works because the wheels push the propeller and in turn the propeller turns the wheels.”)
<> I still don’t believe it
O.K.
>> This is a hoax.
Wrong. I don’t think we’re smart enough to fool Stanford, SJSU, Discovery, WIRED, Popular Science, NASA…
>>
If this is true the only explanation I see is that the propeller is acting as a sail going crosswind.
<>
Easy, have the car first stay still while the wind is blowing, then once it starts, it uses the saved energy to move.
<>
They should have used one of the other photos.
On the one shown the orange tape and wind
instrument shows car is slower then the wind
when the picture was taken.
<<
Worse yet – the cart is actually sitting still in that pic.
Wow – somehow I managed to mangle the formatting and lost a lot of my reply.
The explanation does seem a bit circular – but it’s more like an externally powered feedback loop. The wind provides the power to that loop – but not in a way that’s terribly intuitive.
>>If this is true the only explanation I see is that the propeller is acting as a sail going crosswind.
—
Almost exactly right. The blades of the prop follow a continuous spiralling downwind tack (technically a broad reach).
As to saved energy – our vehicle actually is not capable of acceleration using stored energy.
I saw a toy-sized gadget in Scientific American maybe 30 years ago that could sail directly into the wind with propellers. The air propeller acted as a weathervane while turning a shaft, and the underwater propeller was able to force the whole thing against the wind because the water had so much more reaction mass than the air.
Video is hard to find but I found some here:
http://38aa.sl.pt
I understand the principle of sailboats going into the wind. I’ve sailed.
I don’t understand this car. How does it start? Put standard sails on the thing and I understand how you can get it to go faster than the wind and into the wind. Bernoulli proved that.
>> Video is hard to find but I found some here:
I posted another of our videos, but I guess the moderators didn’t like mine(?)