A vehicle which breaks the laws of physics...

[Keith 66]

Windmill powered boats have been around for a long time, the windmill drives a propellor, they are not very efficient though.
A friend of my late father in law went so far as to build one & try to market it, The Multihull company , plymouth. The prototype was in Guernsey until recently, may still be there.
As for sailing faster than the wind the sailing landspeed record of 126.2 mph was set by Greenbird in 2009.
Sailrocket 2 did 65 knots, the interesting thing about her was the fuselage was angled so it faced directly into the apparent wind at full speed, she appeared to be going crabwise but the whole "boat" had the drag coefficient of a sphere .75 of a meter in diameter. Video here of her & pilot Paul Larsen doing their thing.
,

 

[Screwdriver]

I can't say I fully grasp what's going on but I believe it's possible if you can build a device to collect energy from the wind with respect to the ground, not with respect to the vehicle velocity, you can then travel faster than the velocity of the wind.

My understanding goes along the following:

Imagine the fan is a sail, the wind blows perpendicular to the sail (no tacking) and the vehicle is blown along. The wheels are attached to the fan so that it can be driven, by the wheel rotation, to spin the fan in a direction which blows air backwards.

While the direction of the wind pushing against the fan blades would ordinarily tend to cause them to rotate "with the wind", it does not do that because the blade is already spinning in the "wrong" direction. Because it is spinning the wrong way, it is generating a draught of air against the prevailing wind. This draught is positively drawing air from ahead of the vehicle and crucially, creates a huge "cushion" of air which the prevaling wind is blowing against. The prevailing wind does not blow against the spinning prop, it blows against the massive cushion of air the prop is generating.

There is some crazy aerodynamic effect which, a bit like the wake on a boat, draws air towards this anomaly on an otherwise flat plane. Similar to the venturi effect, this "funneling" of the air surrounding the vehicle extracts energy from around the craft and increases the velocity in one much smaller volume i.e. immediately surrounding the vehicle. I suppose it might even be similar to a whirlwind where huge volumes of air meet and exchange their relative velocity in one tiny spot.

The upshot is the craft is able to power itself ever faster. In fact (and this relates to your comment about "perpetual motion") in theory and under idealised circumstances (frictionless gears, tyres, infinite flat plane etc.) the velocity of the vehicle will keep increasing - without limit!

 

[Munkul]

My understanding goes along the following:

Imagine the fan is a sail, the wind blows perpendicular to the sail (no tacking) and the vehicle is blown along. The wheels are attached to the fan so that it can be driven, by the wheel rotation, to spin the fan in a direction which blows air backwards.

While the direction of the wind pushing against the fan blades would ordinarily tend to cause them to rotate "with the wind", it does not do that because the blade is already spinning in the "wrong" direction. Because it is spinning the wrong way, it is generating a draught of air against the prevailing wind. This draught is positively drawing air from ahead of the vehicle and crucially, creates a huge "cushion" of air which the prevaling wind is blowing against. The prevailing wind does not blow against the spinning prop, it blows against the massive cushion of air the prop is generating.

There is some crazy aerodynamic effect which, a bit like the wake on a boat, draws air towards this anomaly on an otherwise flat plane. Similar to the venturi effect, this "funneling" of the air surrounding the vehicle extracts energy from around the craft and increases the velocity in one much smaller volume i.e. immediately surrounding the vehicle. I suppose it might even be similar to a whirlwind where huge volumes of air meet and exchange their relative velocity in one tiny spot.

The upshot is the craft is able to power itself ever faster. In fact (and this relates to your comment about "perpetual motion") in theory and under idealised circumstances (frictionless gears, tyres, infinite flat plane etc.) the velocity of the vehicle will keep increasing - without limit!

Yes of course it works on the principle that an object moves to a lower pressure area from a higher pressure area.

I like that last point you make. Like you say, remove all losses and friction, and you will get a steady rate of acceleration to an infinite velocity, given a constant supply of wind And of course, it's still not perpetual motion, lol

 

[hotponyshoes]

It's noting like perpetual motion as it needs a constant source of energy input (the wind) to keep going.

 

[colnerov]

Avi 8
the word Sturgeon is a bit like Brexit...best not mention it.....lol.....
Oh and who was the woman that dressed as a boy that gets compared to Sturgon.....I forget....

Janette Tough as the character Jimmy Krankie.

 

[AVI_8]

Avi 8
the word Sturgeon is a bit like Brexit...best not mention it.....lol.....
Oh and who was the woman that dressed as a boy that gets compared to Sturgon.....I forget....

I try not to mention it as it causes an increase to my blood pressure

 

[slim_boy_fat]

Oh and who was the woman that dressed as a boy that gets compared to Sturgon.....I forget....

One of the Krankies

 

[tom2207]

I like that last point you make. Like you say, remove all losses and friction, and you will get a steady rate of acceleration to an infinite velocity, given a constant supply of wind And of course, it's still not perpetual motion, lol

To infinite velocity and beyond ,,, thats it really Munkul Lightyear wins hands down , that could be the quote of the day.


as we all know '' ye canna change the laws of physics'' ,,,, captain.

 

[tom2207]

Now I just have to post this

 

[Nomad]

The whole thing about moving faster than the wind isn't new :
Article about Blackbird dated 2010 proving it's possible https://www.wired.co.uk/article/faster
Another 2010 article, travelling at 2,8 times wind speed https://inhabitat.com/wind-powered-vehicle-travels-faster-than-the-wind/
Technical article about the theory https://hardware.slashdot.org/story...g-Faster-Than-the-Wind-In-a-Wind-Powered-Cart

Result of the $10k bet https://www.iflscience.com/physics/youtuber-derek-muller-won-a-10000-physics-bet-against-professor/

Video of the original prototype

Interesting topic, thanks for posting it

 

[spork]

Howdy folks. A friend sent me a link to this discussion. I'm Rick Cavallaro. I designed, built, and drove the Blackbird. I've seen hundreds of discussions about it, and this has to be one of the most intelligent I've seen so far. If there are any questions I can answer, I'd be more than happy to try.

 

[PhillipM]

It's noting like perpetual motion as it needs a constant source of energy input (the wind) to keep going.

Yeah it's more like it's using some slight gearing advantage to push back against the wind that's blowing it - probably slowing down quite a wide area of the wind behind it in order to give that energy to a relatively small, slippery vehicle. Normally that would just reverse the prop but the gearing prevents that.

It does seem to me it would only generally work with a very efficient vehicle and probably across a fairly narrow speed range in terms of gearing to the prop and sizing though, as I think you'd have quite a range where the prop just stalls otherwise, or the thing never gets moving to start with - but I might be wrong, I haven't done the maths, just theorising.

 

[spork]

It's a very common misconception that the propeller produces a sort of high-pressure air-buffer for the tailwind to push against (if that's what you mean). The reality is that the airflow through and around the propeller is identical to that of a Cessna in straight and level flight. Once past wind speed, the propeller is operating on the air entering from the front of the vehicle. But it has a huge advantage over the wheels since the propeller is advancing through the air more slowly than the wheels are advancing on the ground.

We did make the vehicle as efficient as possible within our means, but you can have a surprisingly inefficient vehicle that will still go faster than the wind - as long as you don't want to go a lot faster than the wind.

With respect to the narrow speed range, it's actually not terribly sensitive to that beyond destroying itself, and not being able to work successfully in too light of a wind (about 8mph in our case).

 

[PhillipM]

Interesting, the prop must still be extracting energy from the airflow around it rather than the other way around in the Cessna though, to power the thing, so not quite identical?

I'd love to see what the flowfield looks like around that, does it actually flip as you cross windspeed or is it pretty much always the same?

 

[spork]

So this gets a little subtle. Something important to understand about this is that the rotor in this case is always a propeller, never a turbine, from 0 speed to faster than wind speed. Interestingly, there's nothing that fundamentally changes from just below wind speed to just above wind speed. It's true that the propeller is just a bluff body for the wind to push against until the car gets moving. From there, the propeller tips begin to develop attached flow as they speed up. The attached flow moves more and more toward the root as it picks up speed. But the wheels are always turning the propeller - never the other way around (in its downwind configuration).

What's harvesting the energy can be a little subtle too since energy is frame dependent. But keep in mind it's not the wind relative to the cart that's important. The cart is exploiting the energy available at the ground/air interface. It slows the wind relative to the ground. So it leaves a wake of de-energized air. That's where the energy came from.

But the way it does this is by harvesting energy from the ground, and spending that energy in the air. Because the propeller is moving through the air more slowly than the wheels move over the ground, we can trade distance for force - just like any lever.

 

[Munkul]

Hi Rick, thanks for taking the time to join the forum and explain things properly If this is an intelligent discussion, there must be hundreds of extremely stupid discussions around the net

It's a very common misconception that the propeller produces a sort of high-pressure air-buffer for the tailwind to push against (if that's what you mean). The reality is that the airflow through and around the propeller is identical to that of a Cessna in straight and level flight. Once past wind speed, the propeller is operating on the air entering from the front of the vehicle. But it has a huge advantage over the wheels since the propeller is advancing through the air more slowly than the wheels are advancing on the ground.

Interesting, it's a subtle difference indeed between providing a static buffer, or providing thrust.

The thing that baffles me, isn't the fact that your machine works, It's that the principle of "ground-air velocity leverage" (?) that is demonstrated on the treadmill isn't widely understood in this day and age, even though you could teach it to teenagers.
It fascinates me because it's some simple concepts very cleverly tied together.
It seems in this modern world, we are looking towards low differential energy leverage more and more - eg heatpumps moving low temperature energy to higher temperature zones. I'm an engineer but I was well out of school before I really understood how we do work to move thermal energy to where we want it to go - same idea as Blackbird - you're manipulating the source of energy to your own purpose.

 

[8ob]

My point is that the hp is irrelevant as you are barely ever using that 180hp whereas in a boat you'll spend most of the time with the engine close to full load.
Either way we both come out with the same conclusion, that drag losses are massive in a boat

They certainly are on anything powerboatish, then you get something like a fully freighted single cylinder Lister engined barge chugging down the canal with sixty tons on board that will run all day on a couple of gallons of fuel. And the huge container ships that work of at hundreds of mpg per ton moved.Small and fast in the water costs.

Bob

 

[Dev]

Just watched the Veratisium and Xyla Foxlin videos. Interesting stuff, I’m always amazed by the confidence of people saying something is impossible even in the face of data to the contrary.

 

[Keith 66]

With windmill powered boats the relative densities of the air & water are a factor, water being 830 times more dense than air. The windmill turns & extracts power from the wind the power is tranmitted to the propellor which drives the boat forward, apparent wind comes into play, drag of the windmill, mast, gearing & hull resistance means the amount of power & drive is limited.
Catamarans though attractive for such boats due to stability are actually less efficient due to wave drag between the two hulls.
Prime example of this was a few years ago when Guy Martin had a go at the speed record for human powered pedal boat. The team that designed & built the boat used a catamaran when it is already well known that the ideal hull for the application is a long skinny hull stabilised with outriggers or foils.

 

[Burdekin]

Yes of course it works on the principle that an object moves to a lower pressure area from a higher pressure area.

I like that last point you make. Like you say, remove all losses and friction, and you will get a steady rate of acceleration to an infinite velocity, given a constant supply of wind And of course, it's still not perpetual motion, lol

Does it work for a short time only? Do they get up to wind speed and then use drive from the wheels to spin the propeller slightly faster?