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Faster than The Wind - Using only Wind

Two of my good friends have created this mind bending cart that can go faster than the wind powered only by the wind (directly downwind), seem impossible but it is very real - Ride Like the Wind (only faster)

The magic happens at 1:15 in the video DDWFTTW #1 on Vimeo

Err... So what exactly is so special about going faster than the wind? Any good sailboat can do that. For land sailing, I think the record's up around 115 mph.

Quote:

Originally Posted by jamesqf (Post 168881)

Err... So what exactly is so special about going faster than the wind? Any good sailboat can do that. For land sailing, I think the record's up around 115 mph.

You need to follow the links. The key is faster than the wind DEAD DOWNWIND. Sailboats can go faster than the wind only on a reach, not DDW. And only in a planing hull, not a displacement hull. Land sailers the same thing, not DDW.

Thanks Moorecomp I meant to specify that, it is an unusual phenom

I only skimmed it, but I didn't see the real design of how it worked, or the math behind it... yes, I see a video with streamers, but I don't see an air speed indicator and a vehicle speed indicator side by side.
What I do see is prop that drives the wheels, but what drives that prop when you get to 40mph with a 40mph wind? same thing with aerodynamics, if you have a tail wind like that the driver is going to feel no wind on their face so the vehicle could be shaped like a brick and should still work fine!

I would think that it would have gears?

They are working on different blade angles to get the bes performance. More info on their blog. They think this one can get 3x the speed of the wind and a slicked out version could maybe do some amazing things.

Ok, the math behind not being able to be pushed faster then the wind has to do with the fact that once you reach the same speed as the wind then you are in an area that has no air movement, the oposit of this is if you have an air speed indicator on the roof of your car and are going 20mph in to a head wind that is also 20mph it will read 40mph, if you turn around and go 20mph with a tail wind of 20mph the propeller on the air speed indicator will read -0-mph because the air around you will be moving at your same speed, gearing will only help if there is wind to push your propeller, move the same speed as the wind and the wind disappears.
Am I missing something?

It is a mind bender, land sailors can go much faster than the wind on a reach - the wheels drive the propeller and the propeller acts like a rotating sail allowing for the cart to go noticeable fast than the wind that is behind it, if you lifted the back of the cart off the ground the propeller would turn the opposite way and the wheels would spin backward. Sound impossible at first, but it is real, see the videos.

actually I think the wheels drive the prop and the prop creates a virtual sail that always moves backward from the vehicle it sort of steals the forward motion leaving a pool of dead air behind itself

so it's creating a back pressure that the wind is pushing... interesting idea.

Learn a little below.

The physics of sailing

Quote:

How can boats sail faster than the wind? Lots of boats can---especially the eighteen footer skiffs on Sydney Harbour. Ask a sailor how, and he'll say "These boats are so fast that they make their own wind", which is actually true. Ask a physicist, and she'll say that it's just a question of vectors and relative velocities.

Downwind (diagram at left) is easy. If the wind is 10 kt, and the boat makes 6 kt in the same direction, then the crew feels a wind of 4 kt coming over the stern of the boat. The true wind vw equals the speed of the boat vb plus the relative wind vr (see vectors for more explanation). The equation vw = vb + vr tells us the problem: as the boat speed approaches the wind speed, the relative wind drops towards zero and so there is no force on the sail. So you can't go faster than the wind. When the wind is at an angle, we have to add the arrows representing these velocities (vector addition). Upwind (right), exactly the same equation holds: vw = vb + vr.

The faster that the boat goes, the greater the relative wind, the more force there is on the sails, so the greater the force dragging the boat forwards. So the boat accelerates until the drag from the water balances the forward component of the force from the sails.

http://www.animations.physics.unsw.e...iles/fuite.gif http://www.animations.physics.unsw.e...files/pres.gif

I thought I already had a post on here, wondering what theory this works on. It certainly is not featured on the huge blog, so until I see independent verification, instead of whining about somebody's official gearing rules, I'll assume somebody is using mundane magic on the video.

Tack (sailing) - Wikipedia, the free encyclopedia

The blades are "tacking" all the time.

Another term used is apparent wind.

Ryland: "so it's creating a back pressure that the wind is pushing... interesting idea." I had not that it like that - might a good way to think of it.

Bicycle Bob - are you saying you think this is a hoax and what they are claiming is not possible?

Just check out BMW Oracle 2to2.5 X wind speed

I sure wasn't impressed by the blog or any video I've seen, but there seems to be some relevant theory posted at Sailing faster than the wind - Wikipedia, the free encyclopedia
The key seems to be to have the wheel acting as a brake, feeding power to the prop to let it pull. It is a mind-bender, all right. Even worse than sailing upwind, or building iron ships.

...ah, but there's a BIG difference between a "powered" wing and and "powering" wing.