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Old 1st April 2010, 01:00 AM   #1
ynot
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DDWFTTW in a “Real” Wind

A team of Aero students from San Jose State University has built and demonstrated a Directly Downwind Faster Than The Wind cart in a “real“ wind.

http://www.youtube.com/watch?v=7SYvg40NHtc

http://www.youtube.com/watch?v=aDzWh9J1dk4

http://www.fasterthanthewind.org/

Will there still be some that dispute this? . . . Unfortunately I think so
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Last edited by ynot; 1st April 2010 at 01:21 AM.
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Old 1st April 2010, 02:44 AM   #2
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Originally Posted by ynot View Post
Will there still be some that dispute this? . . . Unfortunately I think so
Today specifically? I think so.
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Old 1st April 2010, 02:45 AM   #3
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i hate the thing. i just dont get it.
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Old 1st April 2010, 12:15 PM   #4
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Originally Posted by ynot View Post
A team of Aero students from San Jose State University has built and demonstrated a Directly Downwind Faster Than The Wind cart in a “real“ wind.
I would rather say that it was mainly Spork and ThinAirDesign that built the cart and demonstrated the claim.
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Old 1st April 2010, 01:01 PM   #5
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Ya, I'm amazed, going faster than the wind while going downhill.

The black line is horizontal, red shows the slope of the ground.
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Old 1st April 2010, 01:04 PM   #6
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Originally Posted by roger View Post
Ya, I'm amazed, going faster than the wind while going downhill.

The black line is horizontal, red shows the slope of the ground.


"estimating" the slope of the ground from a video...
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Old 1st April 2010, 01:06 PM   #7
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Oh, so exact measurements are "estimates" now, I see.
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Old 1st April 2010, 01:08 PM   #8
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Originally Posted by DC View Post
i hate the thing. i just dont get it.
I'll try to take a stab at it. I'm sure I'll be corrected if I'm wrong.

The prop and wheels are geared together. If you move the wheels so the cart moves forward, the prop spins in a manner that also pushes the cart forward (pushes air back).

In order for the cart to get started, the wind pushes the cart itself. There's no power from the prop - the whole thing is like a sail. That's easy enough to envision.

As the cart moves faster, the prop moves faster. This generates some thrust. However, this thrust is less than the wind speed. In other words if the wind is going at 10, the thrust from the prop is going to be less. The exact value is key, and beyond me because I've never learned about aerodynamics.

The point is that the thrust of the prop is adding some additional speed to the cart. It's not the sole driving force. So what you have is the wind pushing the cart plus the thrust of the prop. The two added together exceed the wind speed. This works because even as the cart outruns the wind, it's still in the wind (think of a stream rather than single thing "pushing").

The prop energy is derived from the difference between the wind and the ground. One is moving while the other is stationary. No matter where the cart goes in the wind, there is still that difference. Therefore, it can still tap into that energy and transfer it from the wheels to the prop.

It's a clever if impractical feat of engineering.
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Old 1st April 2010, 01:09 PM   #9
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Originally Posted by roger View Post
Oh, so exact measurements are "estimates" now, I see.
Let see is it possibly that the camera was not completely level?
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Old 1st April 2010, 01:11 PM   #10
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It's a joke, fredricks.
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Old 1st April 2010, 07:28 PM   #11
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Impressive work, but nothing surprising. It's obviously possible, just a question of designing the cart well enough.

Originally Posted by UncaYimmy View Post
As the cart moves faster, the prop moves faster. This generates some thrust. However, this thrust is less than the wind speed.
How can thrust - a force - be less than a speed? They don't have the same units.

Quote:
The point is that the thrust of the prop is adding some additional speed to the cart. It's not the sole driving force. So what you have is the wind pushing the cart plus the thrust of the prop. The two added together exceed the wind speed. This works because even as the cart outruns the wind, it's still in the wind (think of a stream rather than single thing "pushing").
When it's going faster than the wind, the force of the wind on the cart's body acts to slow it down.

Quote:
The prop energy is derived from the difference between the wind and the ground. One is moving while the other is stationary. No matter where the cart goes in the wind, there is still that difference. Therefore, it can still tap into that energy and transfer it from the wheels to the prop.
That's right. The essential point is that the work done on the ground by the cart can be less than the work the air does on the cart, because the relative speeds are different.
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Old 1st April 2010, 08:13 PM   #12
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Originally Posted by sol invictus View Post
How can thrust - a force - be less than a speed? They don't have the same units.
It's actually pretty easy to do so long as you're not bogged down with pesky definitions. Would you like me to explain what I meant or can you work it out on your own?
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Old 14th March 2011, 07:25 PM   #13
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The recent Wired article has opened up this topic, and with even more bizarre claims that earlier. See "Planet Oil Barrel" of the Wired article.

The original and long-standing claim was that the cart would travel directly down wind, steady state. That claim included wind tunnel conditions, and that was the basis of the argument over the conservation of energy which such a cart would violate. Sleight of hand has allowed that claim to be dropped in favour of an ad-hoc trail, which does not support the original claim.

None of the former conditions have been met by the recent NALSA trail, and there is evidence of data tampering to disguise the changing wind, and so avoid the obvious rebuttal.

This thread concerns a cart in the wind, and I hope the moderators will keep that in mind. Currently, on other forums, Spork and his posse derail the topic with imaginary carts and cotton reels, to avoid answering to the test itself. One does wonder why if the record is so solid, that Spork feels the need to convince the last men standing.

The question has always been one of thermodynamics, and not simply of speed over land. It has been long established that sail boats can exceed wind speed, but ddw is a specific claim; that must be exclusively tested, and all other plausible explanations eliminated if the claim is to be valid.

The employed wind instruments are designed to meet NIST standards for stationary weather stations, and that poses some problems for the measurements from a moving vehicle, but the NALSA data is all the is available, so I will work with that.

This chart was produced by Spork and not NALSA. TAD had free access to all the data, and that certainly is not acceptable.



The first thing to note is that the cart is about 8 degrees off the wind at the start, and is pushed to above the nominal wind speed of 10mph. As soon as the pushing ceases, acceleration rapidly falls until the wind changes at 588990, at which point the cart begins to accelerate. Note that the cart's acceleration is least when close to ddw. That is contrary to NALSA's conclusion that it is best when ddw.

The straight (black) line between 588990 and 588997, indicates a constant change in wind direction of 10/7 = 1.4 degrees/second. It is not just changing, but turning.For the remainder of the trial, the wind is constantly changing and turning, so opening up opportunities for tacking, crosswinds and momentum storage to be responsible for the performance.

None have been eliminated by NALSA. In fact, the rules allow for at least one plausible mechanism involving the rotor and chassis:

"Comment on Rule S2:... Stored energy in the form of momentum of the yacht, its wheels or other normally moving or flexing parts of the yacht is allowed."

That alone disallows the trial for the purposes of the original claim.

The cart is pushed to 40% of the record speed, and gains 3500J ( in the 295kg chassis) and that is energy external to the wind. That is another violation of the claim, unless the cart is shown later to be steady state, and it is not. Unless the cart reaches a constant speed, it does indeed matter "how it gets to windspeed". The cart is allowed to start when it pleases, be pushed, or wait until short-term wind patterns allow for "success". That is why steady-state is a critical parameter. NASLA concerned themselves with only the top speed, and ignored all else.

There is more to be extracted on that topic, but the record itself, as defined by NALSA, is suspect due to data tampering and instrument limitations.



There are clear differences between NALSA's data and the orange chart.
( I have appended the windspeed data to this chart.)

The NALSA chart shows the wind turns South at 8.8 seconds into the measurement period, but about 4 seconds on Spork's chart. The measurement point at 589065.8, also shows different wind patterns at that time.

The NALSA chart shows the wind changes rapidly; 20 degrees in 0.2 seconds, if the data is correct. That is not ddw, nor like a wind tunnel no matter how "averaged". With that level of energy input, the question of the Conservation of Energy becomes moot.

For the 10 second test period, NALSA use a "10 second average" which is simply the arithmetic mean of all the samples within that period, resulting in -4.1 degrees. That is meaningless in any context.
NALSA's chart is the difference of cart and wind. Averaging, as NALSA have done, would allow a jibing cart to average to zero.

But, that is quite obviously not the method used to obtain the wind data in Spork's chart. A likely explanation for the delay, and the smoothed wind changes, is that the data has been low-pass filtered. That process has not been made explicit, and is a violation of NALSA's regulations.

It is claimed that the cart accelerates through the speed measurement period of 3 seconds. That will be hard to sustain. The GPS speed data, from which the acceleration is derived, is updated once a second (1Hz). NALSA took the extraordinary step of interpolating that to 5Hz.
The GT31's speed "accuracy" is given at 0.1m/s, but that is subject to many factors that are perhaps best explained later. But, it is too low to support the small change in speed, and so prove acceleration.

Spork may claim that he has "some sort of record" forged between he and NALSA, but has not met his original claim, yet he allows the names Prof Allain and Charles Platt to be sullied upon that basis. He can keep his "record" but should withdraw his remarks concerning proving anything,
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Old 15th March 2011, 01:27 AM   #14
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Humber's observations might carry some weight if only the cart barely exceeded these supposedly erroneous windspeed measurements. In fact the cart reached 2.8x windspeed.

It works, as indeed it should work. Though it's very counter-intuitive on even the fifth glance and eight explanation.

Humber has devoted years and countless posts of DDWFTTW denial in the endless discussion of this matter over at the talkrational forum and is frantically seeking an 'out', however flimsy.

The ThinAirDesigns guys did a treadmill test - starting about 30 seconds in -
YouTube Video This video is not hosted by the ISF. The ISF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.
I AGREE

that really rendered the life-size design redundant. But that would have destroyed all the fun and satisfaction for them

Last edited by GlennB; 15th March 2011 at 01:28 AM.
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Old 15th March 2011, 02:03 AM   #15
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And what is "counter-intuitive" about a tacking cart? The claim was explicit and unequivocal - ddw, steady state. Where there crosswinds on the TM, or is that no longer the model of proof?
In this forum, I described a cart that could exploit short term wind patterns to exceed the wind. The number of multiples is not relevant, only the power limit that governs final speed. That applies to all tacking craft. Ice-carts do it best, because they have the lowest losses. Why would I be surprised by the BB? It's done what I said it would do, and before it was even conceived.
Like so many of the vainglorious articles on this cart, the Wired article maintains that those like Platt, Allain (and Kammen) are "too stubborn to admit they are wrong" when they are not. It's a sham.
BTW. I have a cart that travels up the belt, without a prop. But that is not the topic of this thread.

ETA: About the time. Of what importance is that to you? How many years has James Randi devoted to debunking woo? Patience and persistence are entry level requirements.

Last edited by humber; 15th March 2011 at 02:14 AM.
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Old 15th March 2011, 01:15 PM   #16
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Originally Posted by humber View Post
One does wonder why if the record is so solid, that Spork feels the need to convince the last men standing.
Not true; he's been ignoring you for almost two years now and has no problem at all with leaving you standing in your self-imposed intellectual wasteland.

The real question is why you insist on being the last man? I don't think there's a prize for that.
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Old 15th March 2011, 01:17 PM   #17
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Originally Posted by humber View Post
BTW. I have a cart that travels up the belt, without a prop.

It's a sham.
You somehow mixed up your sentence order; fixed that for you.
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Old 15th March 2011, 02:12 PM   #18
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Originally Posted by mender View Post
You somehow mixed up your sentence order; fixed that for you.
You can go, now that your best work is done.
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Old 15th March 2011, 02:18 PM   #19
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Humber, did you ever figure out that a stationary wind tunnel and a treadmill in still air are precisely the same thanks to relativity? Or do you continue to insist that kinetic energy is somehow absolute?
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Old 15th March 2011, 03:01 PM   #20
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Originally Posted by humber View Post
And what is "counter-intuitive" about a tacking cart?
A prop-powered cart "tacking" with slightly variable and slightly off-true tail winds that manages a peak of 2.8x average windspeed?

Show your maths or show your wind-tunnel trials.
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Old 15th March 2011, 03:12 PM   #21
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Originally Posted by AvalonXQ View Post
Humber, did you ever figure out that a stationary wind tunnel and a treadmill in still air are precisely the same thanks to relativity? Or do you continue to insist that kinetic energy is somehow absolute?
This thread is about a cart in the wind, and meteorological instrumentation.
The TM will be blown out of the water with two carts that travel up the belt, with no prop, sail, or anything else. That is later.

But for now, you may enjoy these videos, which preceded Spork's TM.

http://img163.imageshack.us/img163/7690/u56.mp4

http://img864.imageshack.us/img864/5312/i0i.mp4

Last edited by humber; 15th March 2011 at 03:39 PM.
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Old 15th March 2011, 03:16 PM   #22
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Originally Posted by GlennB View Post
A prop-powered cart "tacking" with slightly variable and slightly off-true tail winds that manages a peak of 2.8x average windspeed?

Show your maths or show your wind-tunnel trials.
The cart accelerates at a near constant 0.1ms-2. That makes it quite easy to show that the KE demand for that acceleration, is a mere 300J/s at 27mph.
That is easily taken from the wind, as the prop blade moves in an out of the higher speed wind, 2 or 3 meters above the ground.
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Old 15th March 2011, 03:16 PM   #23
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Originally Posted by AvalonXQ View Post
Humber, did you ever figure out that a stationary wind tunnel and a treadmill in still air are precisely the same thanks to relativity? Or do you continue to insist that kinetic energy is somehow absolute?
Not only does he think that kinetic energy is somehow absolute, it matters how an object got kinetic energy according to him. He has gotten even sicker since he was last here.
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Old 15th March 2011, 03:35 PM   #24
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Originally Posted by Subduction Zone View Post
Not only does he think that kinetic energy is somehow absolute, it matters how an object got kinetic energy according to him. He has gotten even sicker since he was last here.
You can hawk your gossip elsewhere. Post if you have something to say about wind vane and anemometer dynamics.

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Old 15th March 2011, 03:47 PM   #25
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humber, do I need to link about your complaints about how the velocity the cart gained by pushing should be subtracted off of its velocity in the record run?
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Old 15th March 2011, 04:01 PM   #26
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Originally Posted by Subduction Zone View Post
humber, do I need to link about your complaints about how the velocity the cart gained by pushing should be subtracted off of its velocity in the record run?
Not for humber, but can you do it for laffs for the rest of us who missed it?
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Old 15th March 2011, 05:09 PM   #27
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Originally Posted by GlennB View Post
Not for humber, but can you do it for laffs for the rest of us who missed it?
While at it, SZ may also link to the posts at TR where humber claimed that if you put, for example, a 10 kilogram weight on two stacked scales, each one will only read 5 kilogram. Because that is how springs work, he says. Really, i'm not kidding you.

Greetings,

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Old 15th March 2011, 05:48 PM   #28
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Originally Posted by Christian Klippel View Post
While at it, SZ may also link to the posts at TR where humber claimed that if you put, for example, a 10 kilogram weight on two stacked scales, each one will only read 5 kilogram. Because that is how springs work, he says. Really, i'm not kidding you.

Greetings,

Chris
The humberverse must be a fascinating place.
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Old 15th March 2011, 05:55 PM   #29
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Originally Posted by humber View Post
This thread is about a cart in the wind, and meteorological instrumentation.
The TM will be blown out of the water with two carts that travel up the belt, with no prop, sail, or anything else. That is later.

But for now, you may enjoy these videos, which preceded Spork's TM.

http://img163.imageshack.us/img163/7690/u56.mp4

http://img864.imageshack.us/img864/5312/i0i.mp4
Seriously? You think the videos of the cart with two wheels on a stationary surface and one on a belt sander remaining stationary until the belt sander is speeded up prove something about the ddfttw carst? Please explain. It should be humorous.
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Old 15th March 2011, 06:13 PM   #30
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Originally Posted by Subduction Zone View Post
humber, do I need to link about your complaints about how the velocity the cart gained by pushing should be subtracted off of its velocity in the record run?
Already in the text. The cart never reaches steady state, so still under the influence of initial conditions. V =at, where a is the sum of all accelerations.


If the cart were not pushed, but only accelerated at the rate after that, then
it would obviously not reach the same speed. Steady-state was a loudly trumpeted claim, but now the cart fails to perform as hoped, the claim has been reduced to meet that.

But, there is nothing at all interesting about this cart reaching some multiple of WS, because it tacks the wind, like so many other sail craft

However, as a "record", for whatever that is worth, there will be problems should there be any future contestants. They will argue about how much influence the pushing had, don't you think? It's pushed to 40% of the record. The trail method is unsound, and unrepeatable, so worthless from any point of view.
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Old 15th March 2011, 06:14 PM   #31
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Originally Posted by CORed View Post
Seriously? You think the videos of the cart with two wheels on a stationary surface and one on a belt sander remaining stationary until the belt sander is speeded up prove something about the ddfttw carst? Please explain. It should be humorous.
It is no different. You just think it is. And the topic is a cart in the wind,
not TM's.
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Old 15th March 2011, 06:33 PM   #32
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Originally Posted by humber View Post
But, there is nothing at all interesting about this cart reaching some multiple of WS, because it tacks the wind, like so many other sail craft
Because you imagine that to be the case? Are you there measuring the direction of the wind? Do you have any evidence to back that up?
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Old 15th March 2011, 06:47 PM   #33
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Originally Posted by humber View Post
It is no different. You just think it is. And the topic is a cart in the wind,
not TM's.
Oh, I get it. You still haven't figured out that the cart with the propeller was moving in the opposite direction of the belt.
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Old 15th March 2011, 06:50 PM   #34
Subduction Zone
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Originally Posted by GlennB View Post
Not for humber, but can you do it for laffs for the rest of us who missed it?
I will link a post of his that claims this. It is at the bottom of the post if you want to skip ahead. I don't want to copy and paste his rant for everybody to see here, there may be innocent women and children reading this

http://talkrational.org/showpost.php...&postcount=746
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If you "feel" 1G for 1sec, how far you travel depends only on your mass.
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Old 15th March 2011, 06:53 PM   #35
CORed
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Originally Posted by GlennB View Post
A prop-powered cart "tacking" with slightly variable and slightly off-true tail winds that manages a peak of 2.8x average windspeed?

Show your maths or show your wind-tunnel trials.

So, no test is valid unless it's conducted in a "real" wind, but the test is invalid if the velocity or direction of the wind changes a little bit, which just about always happens with "real" wind. Nice.
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Old 15th March 2011, 07:48 PM   #36
humber
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Originally Posted by Molinaro View Post
Because you imagine that to be the case? Are you there measuring the direction of the wind? Do you have any evidence to back that up?
Plenty. Take a look at the orange chart. The cart does not spend one second ddw. The wind is the black serpentine line. It should follow that.

Not suitable or possible? Probably not, but then, it's not suitable to the task of proving ddwfttw.There are no second prizes.

Spork has admitted that the conditions were not suitable, saying that the wind was "crossed", but he followed the course he was told to follow.

The only wind data that is actually NALSA's, is the last 10 seconds. They average that, to -4.1 degrees, but you can't do that to vectors. The RMS value is 8.8 degrees, not -4.1 degrees. The wind data alone ( not the difference of cart and wind) produces 11.02 degrees. The chart was produced by Spork not NALSA, and it is clear that he tampered with the data. I don't need to be there to see that.

The vane is designed for fixed use, and to meet NIST standards. For mobile measurements, pitot tubes or acoustic devices are necessary. The mechanical response of the vane can be known, and that, I do know.
The wind deviation will be higher than indicated. There is nothing about this cart that says anything but a sail cart, tacking the wind.

Last edited by humber; 15th March 2011 at 07:51 PM.
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Old 15th March 2011, 08:34 PM   #37
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Originally Posted by humber View Post
You can hawk your gossip elsewhere. Post if you have something to say about wind vane and anemometer dynamics.
Like how you think a balanced weather vane will be forced to show a more direct headwind by acceleration?

Or how a 650 lb cart is more sensitive to changes in wind than high performance meteorological measurement devices?
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Old 15th March 2011, 10:41 PM   #38
humber
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Originally Posted by Llyricist View Post
Like how you think a balanced weather vane will be forced to show a more direct headwind by acceleration?
I don't think you are up to the mathematical explanation, LLyricst, so I will show you diagrammatically.



The additional force due to acceleration, suppresses the deviation, and there is no means of getting the correct answer, unless at least all of the transient behavior is recorded. The sampling rate is only 5Hz, and that means a bandwidth of less than 2.5Hz. In wind tunnel testing of vanes, the sampling rate is 350Hz or greater.
NALSA have no way of knowing the apparent from the real, and that is that. A fundamental error.
Attached Images
File Type: png jref_vane.png (28.6 KB, 1098 views)

Last edited by humber; 15th March 2011 at 10:42 PM.
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Old 15th March 2011, 10:50 PM   #39
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Do you have any idea what the term "balanced" means?
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Old 15th March 2011, 10:54 PM   #40
humber
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Originally Posted by Llyricist View Post
Do you have any idea what the term "balanced" means?
It seems you don't. A vane is not balanced in any way that affects the result of acceleration. There is a mass at one end, and a vane at the other. Force on the vane create torque that accelerates the mass. There is no "balance" other than static. It's a second-order device, and will oscillate when a transient is applied. As I said, the math is not for you, but you seem to think that off-the-cuff generalities will cover a topic that is completely foreign to you.
NALSA are not a testing lab. They don't have any certification at all.

Last edited by humber; 15th March 2011 at 10:57 PM.
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