"Faster than the wind," impossible they say but the Blackbird settles the debate

[aerohead]

Originally Posted by RedDevil

None of this addresses what was in the post you replied to.
But I'll reply to yours point for point. The first two hit the essence.

... it is the 'triangular sails- propeller blades' that are responsible for Blackbird's motion.

Yes, but you have to understand in what way they are responsible.

The car is moving faster than the wind, but as the propeller spins backwards the surface of the blades is moving slower than the wind.
So the wind pushes against the blades, forcing the car forward.
--------------------------------------------------------------------------------------
2) The wheels cannot power the propeller if the propeller is the sole source of power for the wheels.

The forward vector of the force on the blades powers the car forward, the sideways vector works against the gears that push the propeller against the wind. If the gearing is set so that the surface of the blades still moves forward, albeit slower than the car and of course slower than the wind, the force fighting the rotation is less than the forward pull on the blades.

The forces would be equal if the propeller would force the air backwards at the same speed as the car is moving.
The optimal setting is just slightly less than that; the friction in the system determines how much less it needs to be to function.
--------------------------------------------------------------------------------------
3) If you examine turbine blades and propeller blades, you may find that their airfoil geometries are 'reversed.'

This is not a turbine. The propeller does not harvest energy through rotation, but through forward pull.
--------------------------------------------------------------------------------------
4) In a bonafide powerplant failure during flight, in a variable-pitch propeller aircraft, the aircraft checklist instructs the pilot to 'de-pitch' the prop, in order
to reduce prop-drag, thereby increasing glide radius for a dead-stick landing.

A powerless plane has no surface that moves with a different speed to the wind to do anything with, what renders their propellers useless. Putting them in vane position is the only sensible thing to do in that scenario.
-------------------------------------------------------------------------------------
5) The 'Blackbird' propeller analogy implies that, in a flight emergency, the pilot would merely 'reverse' the propeller ( like a Lockheed C-130 Hercules ), and the free-wheeling reversed propeller would now be capable of maintaining enough thrust for level flight.

Second flight analogy, but again if you have no fixed surface moving at a different speed than the wind you have no source of power.
-------------------------------------------------------------------------------------
6) The 'masts' which hold the aircraft propeller are free to move in relation to the aircraft fuselage.

Third flight analogy. It is a flight away from the core mechanism at work.

* That the car is travelling faster than the wind has never been scientifically ascertained.
* I've provided a fluid mechanics explanation for the phenomena of the backwards-facing tattle which doesn't require the car to be exceeding the wind speed.
* And I've provided video documentation, illustrating this phenomena in action.
--------------------------------------------------------------------------------------
Any argument in favor of the veracity of Rick Cavallero's 'evidence' ought to begin with independent, 3rd-party verification of results.

*' A wise man proportions his belief to the evidence.' David Hume
* Data used cannot be influenced by hidden factors or be an artifact of the way the data were collected.
* Observational study claims are not based upon experimental study.
* The relationship must hold true in any and all studies unless there's a valid reason for it to break down under certain circumstances.

[freebeard]

I've gotta say I don't care about this, but I notice that Youtube's algorithm cares because these stories hit [my custom] front page together. Integza:

https://www.youtube.com/watch?v=QHJka4_ZioU

And Xyla Foxlin

https://www.youtube.com/watch?v=VUgajGv4Aok

So now I guess I'll care a little bit.

[RedDevil]

Originally Posted by aerohead

* That the car is travelling faster than the wind has never been scientifically ascertained.
* I've provided a fluid mechanics explanation for the phenomena of the backwards-facing tattle which doesn't require the car to be exceeding the wind speed.
* And I've provided video documentation, illustrating this phenomena in action.
--------------------------------------------------------------------------------------
Any argument in favor of the veracity of Rick Cavallero's 'evidence' ought to begin with independent, 3rd-party verification of results.

*' A wise man proportions his belief to the evidence.' David Hume
* Data used cannot be influenced by hidden factors or be an artifact of the way the data were collected.
* Observational study claims are not based upon experimental study.
* The relationship must hold true in any and all studies unless there's a valid reason for it to break down under certain circumstances.

The chase car behind the Blackbird with wind speed meters at several height levels all showing that they were going way faster than the wind should be enough proof.

You want proof because you fail to grasp the mechanics of this car. If you understood them then you would know it can work, and should work if constructed correctly.

Your fluid dynamics video is not based on the same principle as what is at work here. I don't know why you think it is.

It is a bit like trying to explain the mechanism of natural selection to someone who believes the species are created by God and immutable. No proof would be good enough, while those who understand the logic behind natural selection don't need proof. They rather predict what may happen in certain situations and will only run experiments to confirm what they understand.

[aerohead]

1) still no instrumented airspeed/ ground speed.
2) no instrumented downwind velocity exceeding air velocity on a stationary dirt surface.

[freebeard]

Still don't care. I'll watch Xyla Foxlin anyway.

[aerohead]

1) I saw no instrumentation on either of the support vehicles.
2) I did see one hand-held anemometer.
3) One wind sock.
4) The backwards-facing Mylar and yarn tattle is not 'proof' of exceeding the wind speed, only that both are pointing into a region of lower pressure, which can be explained by other effects.

[aerohead]

Originally Posted by freebeard

Still don't care. I'll watch Xyla Foxlin anyway.

He has a very good stage presence.

[RedDevil]

The misconception some people have is that if you have two bodies that are moving relative to one another, that any object that is in touch with both and nothing else cannot move beyond the speed of either.

So we have the ground at standstill, and the wind at a steady pace, and nothing can move against the wind or faster than the wind.

Now if we substitute the wind for a wooden plank, that would mean if you put something in between the ground and the wooden plank and you pusth the plank over that object, it would not move faster than the plank.
Right?

Behold my super simple car:



Note it has a double set of wheels; one in touch with the ground, one in touch with the plank. But the upper set also rests on a disk that is attached to the lower set of wheels, but half its size.

Now if you move the car then the upper wheels will turn at half the speed of the lower wheels and in the opposite direction. As the plank rests on those wheels, it will move in the same direction as the car but at half the speed.
That should be obvious.

Now what happens if you don't push the car, but rather the plank?
Of course the car will shoot away at twice the speed of the plank! Because the plank and car will still move relative to each other with the same ratio as when you push the car.

The wind does not provide as much grip as a wooden plank does, but if your propeller is big enough and other sources of friction are low then it would work just the same.

[California98Civic]

The $10,000 bet with a UCLA Prof that the project doesn't work. The video is pretty remarkable. I don't want to spoil anything.

https://m.youtube.com/watch?v=yCsgoLc_fzI

[RedDevil]

Boom! mind blown!

9:55: "Also, in 2013 the US Physics Olympics Semifinal Exam asked questions about Blackbird. Like, can it go faster than the wind downwind, and upwind? ..."

I was a participant in the 1983 International Physics Olympiad in Bucharest, Romania, having qualified 4th in the Dutch Physics Olympiad that year. It is a pity they did not bring this very subject up in the final round, I feel it would have increased my chances