Downwind faster than the wind. Poll

[Marsupial]

If the wind stopped, it would not work outside either. But that's the point, the energy, whether from the treadmill or from the wind, is input continuously.

The trick is to use that energy to obtain more speed. In this case more speed than the wind, (or treadmill) but not more energy than the wind.

yes but its not getting any ernergy from the wind, any wind in this system is an illusion up or down!

 

[RAI]

yes but its not getting any ernergy from the wind, any wind in this system is an illusion up or down!

On the treadmill, the energy comes from the treadmill. In the video of the same device outside in a wind, the energy comes from the wind.

 

[Ubergeekian]

It's impossible. I don't see how any machine with frictional losses (and they all have) can get through the null period between a true following wind and an apparent headwind.

That's because you are falling into the error (and it's easy to do, don't feel bad about it) of thinking that the power supply is the wind. It's not - it's the wind/water speed differential that does it, and that's still there when the vessel is at wind speed.

It's all very counterintuitive.

 

[Porthandbuoy]

About the ability of BMW Oracle to reach a point dead downwind faster than the wind itself?

No, not that. Simply the apparent claim that something is producing more energy from a system than it extracts.

Come on, what happens in a gust?

 

[RAI]

No, not that. Simply the apparent claim that something is producing more energy from a system than it extracts.

Come on, what happens in a gust?

It is not producing energy it's extracting it. It uses the extracted energy to produce speed. As speed is not energy, it could, just like BMW Oracle does go faster downwind than the wind does.

 

[Ubergeekian]

No, not that. Simply the apparent claim that something is producing more energy from a system than it extracts.

Who has claimed that?

 

[bbg]

To you true believers - the OP (of the other thread) was NOT talking about a VMG faster than the wind. He was talking about Dead Down Wind Faster Than The Wind (DDWFTTW).

I hope we would all agree that, when the vessel (vehicle, whatever) is moving DDW at exactly the wind speed, it see NO apparent wind. None. Remember, we are not talking BMW / Alinghi like performance of gybing downwind on very broad reaches with high apparent wind speeds. We are talking about DEAD DOWN WIND. So - can we agree on this? The vessel, and all of its components, see NO apparent wind. Ignoring the interface for a moment, it is just as if it is sitting in a room with no wind. Agreed? Yes or no?

Personally, I think the propellor on such a system won't turn, and if it is turning it will eventually slow down and stop. Agreed? Yes or no?

Now, if there is no wind energy being input into the system, the only other source of energy is the kinetic energy of the vessel itself. As I understand this system, the idea is to extract that kinetic energy (through geared wheels) which drive the propellor to impart thrust. The problem is that there will be frictional losses (rolling resistance, in the gears, inefficiency of propellor) that means that the thrust imparted will be less than the drag created.

I still think the OP of the original post is a very effective troll - he doesn't even have to keep plugging his position. Others are now doing it for him.

NOTABLY - neither the OP nor the website provide the mechanism for going DDWFTTW. The mechanism for getting a VMG faster than the wind is pretty easy to explain and understand. These guys don't. They are winding everyone up and they know it. It is a big practical joke.

 

[johnabbott893]

To you true believers - the OP (of the other thread) was NOT talking about a VMG faster than the wind. He was talking about Dead Down Wind Faster Than The Wind (DDWFTTW).

I hope we would all agree that, when the vessel (vehicle, whatever) is moving DDW at exactly the wind speed, it see NO apparent wind. None. Remember, we are not talking BMW / Alinghi like performance of gybing downwind on very broad reaches with high apparent wind speeds. We are talking about DEAD DOWN WIND. So - can we agree on this? The vessel, and all of its components, see NO apparent wind. Ignoring the interface for a moment, it is just as if it is sitting in a room with no wind. Agreed? Yes or no?

Personally, I think the propellor on such a system won't turn, and if it is turning it will eventually slow down and stop. Agreed? Yes or no?

Now, if there is no wind energy being input into the system, the only other source of energy is the kinetic energy of the vessel itself. As I understand this system, the idea is to extract that kinetic energy (through geared wheels) which drive the propellor to impart thrust. The problem is that there will be frictional losses (rolling resistance, in the gears, inefficiency of propellor) that means that the thrust imparted will be less than the drag created.

I still think the OP of the original post is a very effective troll - he doesn't even have to keep plugging his position. Others are now doing it for him.

NOTABLY - neither the OP nor the website provide the mechanism for going DDWFTTW. The mechanism for getting a VMG faster than the wind is pretty easy to explain and understand. These guys don't. They are winding everyone up and they know it. It is a big practical joke.

Very well put but I think you are wrong. The perps are from the US of A. They usually beleive the bull that they come out with.

 

[RAI]

When this device is moving downwind at the wind speed its structure sees no relative wind.

But the rotating blades of its propeller are always seeing an apparent wind. The apparent wind vector diagram, of blade rotational speed and wind speed and the lift and drag vectors on the blade are similar to those on BMW Oracle's wing and sails. A forward force is generated.

Just as BMW Oracle can produce more down-wind VMG than the wind's speed, the propeller blades could achieve greater VMG down-wind than the wind speed. If they do, then the axel of the propeller must be moving down-wind faster than the wind.

 

[Ubergeekian]

I hope we would all agree that, when the vessel (vehicle, whatever) is moving DDW at exactly the wind speed, it see NO apparent wind. None. Remember, we are not talking BMW / Alinghi like performance of gybing downwind on very broad reaches with high apparent wind speeds. We are talking about DEAD DOWN WIND. So - can we agree on this? The vessel, and all of its components, see NO apparent wind. Ignoring the interface for a moment, it is just as if it is sitting in a room with no wind. Agreed? Yes or no?

Yup.

Personally, I think the propellor on such a system won't turn, and if it is turning it will eventually slow down and stop. Agreed? Yes or no?

No, because it's not a child's windmill. It's connected to a propellor in the sea.

Now, if there is no wind energy being input into the system, the only other source of energy is the kinetic energy of the vessel itself.

As several of us have said, several times, it's not the wind speed that drives things, it's the difference between the wind and the water speed.

As I understand this system, the idea is to extract that kinetic energy (through geared wheels) which drive the propellor to impart thrust. The problem is that there will be frictional losses (rolling resistance, in the gears, inefficiency of propellor) that means that the thrust imparted will be less than the drag created.

You are confusing thrust/drag (forces) with energy.

 

[bbg]

When this device is moving downwind at the wind speed its structure sees no relative wind.

But the rotating blades of its propeller are always seeing an apparent wind. The apparent wind vector diagram, of blade rotational speed and wind speed and the lift and drag vectors on the blade are similar to those on BMW Oracle's wing and sails. A forward force is generated.

I'm with you right up to here. Imagine this contraption in a room with no air movement (say a big auditorium). Blades are spinning. It is strapped to the ground (not moving across the ground) to make sure that it continues to see the same apparent wind speed - none. I agree with you that it produces thrust (i.e. it will try to move forward). But it does NOT continue to produce thrust. The blades slow down and eventually stop.

 

[bbg]

Very well put but I think you are wrong. The perps are from the US of A. They usually beleive the bull that they come out with.

No, I'm pretty sure they DON'T believe it, and it is all a big practical joke. This is the quote taken from their website:

Can a vehicle be built which can go directly downwind, faster than the wind, powered only by the wind(DDWFTTW), steady state? A team of Aero students from San Jose State University, their professor and advisors, along with generous corporate sponsors have set out to definitively answer this question. Follow their quest over the last quarter of 2009 and first quarter of 2010

NOTE - they don't claim it can be done, they ask a question and "set out to definitively answer" it. They also say their quest will be over the last quarter of 2009 and the first quarter of 2010. Very specific timing. The first quarter of 2010 ends on 31 March. The next day is 1 April. I allow you all to draw your own conclusions.

Edit - Note also their generous corporate sponsors: Joby Energy, a "company" that has a bizarre wind-turbine technology itself, and has no history that I can find before December 2009. The kind of company that is LOOKING for money - not the kind that would be giving money away. A "sponsor" that seems to have been created for this practical joke.

All of you true believers are going to be eating some crow in 17 days.

 

[RAI]

I'm with you right up to here. Imagine this contraption in a room with no air movement (say a big auditorium). Blades are spinning. It is strapped to the ground (not moving across the ground) to make sure that it continues to see the same apparent wind speed - none. I agree with you that it produces thrust (i.e. it will try to move forward). But it does NOT continue to produce thrust. The blades slow down and eventually stop.

Of course, in your example there is no more energy to capture and convert.

But in this experiment, the wind continues to blow over the ground. The propeller is connected to the ground via a gearbox and friction. Hence it has a way to tap into the energy of the wind. Were it not, then it would not work. If it was just a trolley with an umbrella on it could not exceed wind speed. The propeller is not being driven by the wind, it is driving against the wind.

The experiment is to see if a machine can be built to carry a person, rather than the models shown in the videos.

 

[bbg]

The experiment is to see if a machine can be built to carry a person, rather than the models shown in the videos.

No - the experiment is to see how many people will fall for the illusion. Perhaps I am contributing by engaging in the debate.

My prediction is that, even AFTER the "researchers" declare it to be impossible, and a practical joke, many people will STILL claim it is possible.

 

[HoratioHB]

Lets all wait until 1 April and the reopen the debate!!

 

[xxyyzz]

I hope we would all agree that, when the vessel (vehicle, whatever) is moving DDW at exactly the wind speed, it see NO apparent wind. None.

Aye, but its wheels are going ten to the dozen and driving the bloody great prop.

Now, imagine if you stuck the device in dead still air, with the prop turning, it will move yes?

 

[bbg]

Aye, but its wheels are going ten to the dozen and driving the bloody great prop.

Now, imagine if you stuck the device in dead still air, with the prop turning, it will move yes?

Quite. But a prop is a pretty inefficient way of imparting thrust. Much more efficient to have those wheels (which are going ten to the dozen) driving some other wheels.

 

[RAI]

Quite. But a prop is a pretty inefficient way of imparting thrust. Much more efficient to have those wheels (which are going ten to the dozen) driving some other wheels.

Obviously would not work as there would be now way to use the wind speed over the surface.

But that is what this device does. It uses the energy difference between either stationary road and wind or between moving treadmill and still air.

 

[xxyyzz]

Quite. But a prop is a pretty inefficient way of imparting thrust. Much more efficient to have those wheels (which are going ten to the dozen) driving some other wheels.

That would work, if there were an additional surface to place the wheels against and that is stationary relative to the cart.

If you imagine the treadmill running at the bottom driving wheels attached to the top of the cart, the wheels on top of the cart are moving. Now place a board against the top wheels like a ceiling, so we have a stationary ceiling with wheels geared to wheels running on the moving floor.

 

[trapezeartist]

I met a person once who knew a person who had seen a demonstration of a car that ran on water as its fuel. He really saw it: they poured water into the petrol tank, started the engine and drove it. Absolutely true, real, for sure.