Downwind Faster Than The Wind

This is our entry into the MythBusters viral video challenge.

Category:

Science & Technology

Tags:

• DDWFTTW
• DWFTTW
• Downwind
• Mythbusters

[cyrustelk]

Hey Clutch, you're missing the point. Iceboats for example CERTAINLY can travel faster than the wind when they are just off the wind (on a beam reach for example). The key here is: can any machine powered only by the wind overcome resistance to travel DIRECTLY downwind any faster than the wind. I had always thought it impossible, but I don't see any trickery with the Goodman machine. PS Are you the same Goodman that did the water injection system from 60 minutes some 10 years ago?

[TraderTurok]

I am not Jack Goodman, but I am familiar with him and it's not the same Jack.

JB

[WCCobra]

How can one claim the vehicle is powered solely by the wind when it is clearly propelling itself with a propeller. The propeller is pulling the vehicle forward even when the wind dies down (unlike a balloon).

[TraderTurok]

Just as a boat under sail it powered by 'wind' (more accurately by the relative motion between water and air), this device is also powered by wind (more accurately by the relative motion between rolling surface and air)

There is no external input of power besides that of this relative motion.

JB

[clutchtusz]

This is no myth whatsoever. Look at sailboats. Plenty of them can sail downwind faster than the wind and some can sail upwind faster than the wind. Apparent wind is the driving force.

[TraderTurok]

Absolutely correct -- ice-boats and land-yachts can achieve downwind VMG (velocity made good) speed of more than 3x the wind.

Top of the line racing sailboats are now regularly able to achieve VMG speeds greater than 1.0.

And still almost everyone claims it can't be done and that it would constitute perpetual motion if it could.

JB

[kmarinas86]

@TraderTurok

"And still almost everyone claims it can't be done and that it would constitute perpetual motion if it could."

Because they think know what would produce perpetual motion. They confuse speed with energy. Energy is a conserved quantity, and speed is not. These people, self-pontificated so-called defenders of scientific fact in fact know very little, if anything about what they claim to preach. Frankly, it is disgusting that as a result they blind themselves from simple observations.

[mikesnowhansen]

This is absolutely true but in those cases it is due to the ability to harness the apparent wind created by moving, and true wind input.

This however is different as it running at the equivalent of directly downwind, so the apparent wind doesn't make the combined angle move 'forward' but instead it cancels out the true wind..

[GeorgeLambadas]

i have a theory but it's only a theory. if someone can prove me right or wrong, please do so because i'm curious.

I believe that the machine can move forward faster than the wind purely due to cumulative power inputs. we can agree that the treadmill is travelling at a uniform rate, as would the wind. the machine on the other hand, is moving quickly as a result of a constant consistent power input. something like pushing someone on a swing. even if the pushes get weaker , they go higher

[jamesdl00]

Thanks!

This is like a physics version of a magic eye picture... once you get it, it's so simple. I think it would help the skeptics to understand that the energy is coming from neither the wind nor the treadmill, but the DIFFERENCE in flow between them. You don't even need 2 different media, ie dynamic soaring can achieve >windspeed velocities by extracting energy from wind shear.

FYI I linked to your vid from sailinganarchydotcom... I think it sparked a debate among sailors over there too.

[jamesdl00]

Actually, I need to correct myself. That would be the same as no wind (if the speed of the wind generated by the fan is equal to the treadmill speed). No one is arguing that the vehicle can travel anywhere in no wind, there must be a differential in flow rate between 2 surfaces.

[TraderTurok]

As a matter of fact it does (as viewed by the cart).

Both Jack's and our devices are powered by the relative motion between the rolling surface and the wind. Disconnect the vehicles from either medium and they stop.

Lift the wheels -- they stop. Take the belt off from the wheels to the prop -- they stop. Disconnect the prop from the gearbox -- they stop.

JB

[lasersailor184]

It's not a perpetual motion machine. Were you to remove the wind, it would stop. What we see here is mechanical advantage, inertia and reduced wind friction from heading dead down wind. Basically, what it relatively is, is a little cart that can move forward against the wind when you spin its wheels for it.