Merged DDWFTTW in a “Real” Wind

[Dr. Keith]

yep, in fact ~60 degrees is where you get your best speeds in the higher winds, and where Jenkins was when he broke the record.

OK, so for a fairly good land yacht to do what BB did they would have to be at about 60 degrees off DDW.

So to do so at only 40 degrees off DDW would be a pretty big achievement and to do so in a wind vacillating such that it is only momentarily 40 degrees off DDW would be near impossible with a standard land yacht, right?

So, even assuming the wind was averaging 20 degrees off DDW this would be a huge achievement for a land yacht, right?

And that would be without the added drag of the prop, as described by humber up thread. You can't get away from the "physics" that the prop is simply a plate that is dragging in the wind. A 4 meter diameter plate, mind you.

Put like this, BB is even cooler than spork and Co have claimed.

 

[Llyricist]

OK, so for a fairly good land yacht to do what BB did they would have to be at about 60 degrees off DDW.

So to do so at only 40 degrees off DDW would be a pretty big achievement and to do so in a wind vacillating such that it is only momentarily 40 degrees off DDW would be near impossible with a standard land yacht, right?

So, even assuming the wind was averaging 20 degrees off DDW this would be a huge achievement for a land yacht, right?

And that would be without the added drag of the prop, as described by humber up thread. You can't get away from the "physics" that the prop is simply a plate that is dragging in the wind. A 4 meter diameter plate, mind you.

Put like this, BB is even cooler than spork and Co have claimed.

Yes, we have pointed this out many times to the resident naysayer, and his response amounts to a flat assertion that a bucket could do it.

 

[humber]

Yachts are off topic.

 

[profpangloss]

Thanks, that is a very cool chart. The winged sail does help me to make better sense of it.

From that graph it seems that the cart has to be more than 60 degrees off DDW to best 2.8x WS in a 10mph wind. Am I reading that right?

I don't know how authentic this quote is. I came across it searching for info on Greenbird:

Greenbird (Jenkins' land/ice boat) obviously has the fastest speed sailing ... But even at 45-degrees to wind direction he's able to get 3X wind speed, and 2X wind speed at 20-some degrees, and 1X at 6-some degrees. ...

Besides that, I am not convinced the wind was 10 mph during the testing of BB. If you look at the way the wind was changing direction, it stands to reason it was gusting also. Does anyone have any info on how high those gusts were?

But lets cut right to the chase here: This record was given for Directly Down Wind. That's all that should matter here. The data clearly shows that did not happen. End of story! Throw the bum out!

 

[Dr. Keith]

Yes, we have pointed this out many times to the resident naysayer, and his response amounts to a flat assertion that a bucket could do it.

Sorry to rehash old arguments, but I hadn't seen this line of thinking before and I don't know much about land yachts.

It does seem a rather damning line of analysis: if you take everything humber says as true the BB is even more amazing than claimed.

Profpangloss: any comment? ETA: comment overlap!!

Thanks.

 

[humber]

Yes, we have pointed this out many times to the resident naysayer, and his response amounts to a flat assertion that a bucket could do it.

You are wasting your time. The claim is for a ddw vehicle and not for anything else. It is already clear that the cart is nowhere near a ddw vehicle and the cart would be outstripped by even a mediocre sail cart.
The sheer desperation of now trying to claim is a magical tacking cart. That won't fly, the record is all but dead.

 

[profpangloss]

Sorry to rehash old arguments, but I hadn't seen this line of thinking before and I don't know much about land yachts.

It does seem a rather damning line of analysis: if you take everything humber says as true the BB is even more amazing than claimed.

Profpangloss: any comment? ETA: comment overlap!!

Thanks.

What in the world do you find amazing about doing something that is done routinely by quite a few different types of land, ice and water yachts? What would have been amazing is if the cart did what was claimed, gone DDWFTTW but it did not do that. The record is a sham and should be retracted.

 

[humber]

I don't know how authentic this quote is. I came across it searching for info on Greenbird:


Besides that, I am not convinced the wind was 10 mph during the testing of BB. If you look at the way the wind was changing direction, it stands to reason it was gusting also. Does anyone have any info on how high those gusts were?

But lets cut right to the chase here: This record was given for Directly Down Wind. That's all that should matter here. The data clearly shows that did not happen. End of story! Throw the bum out!

The cart does nothing exemplary as far as tacking goes. The wind is indeed faster than the 10mph.
Worse still, it that it is measured at hub height, so the prop spends 50% of its time in un-metered gusty wind.
2.25 - 2.5 times the windspeed, with a top speed of only 28mph, is nothing to brag about.
And yes, the entire claim was for ddw, and the only reason for any interest or concerns over thermodynamics. The bums will be thrown out.

 

[Dr. Keith]

I don't know how authentic this quote is. I came across it searching for info on Greenbird:

But it doesn't quote the speeds at which those multiples are achieved and according to the chart above that does matter.

Besides that, I am not convinced the wind was 10 mph during the testing of BB. If you look at the way the wind was changing direction, it stands to reason it was gusting also. Does anyone have any info on how high those gusts were?

My understanding is that vessels like the greenbird would do better in steady winds than gusty winds. At least that was my experience when I sailed.

But lets cut right to the chase here: This record was given for Directly Down Wind. That's all that should matter here. The data clearly shows that did not happen. End of story! Throw the bum out!

Ah, yes. Define DDW so narrowly that it can never be achieved because no wind is consistent enough to satisfy your definition. That is real progress!

I think it is conclusively proven that even by humber's analysis the BB travels at higher multiples of WS in a relatively low wind at closer angles to DDW than any prior land yacht. All while dragging that huge prop through the air. No small feat, even if you take humber's word.

 

[profpangloss]

But it doesn't quote the speeds at which those multiples are achieved and according to the chart above that does matter.



My understanding is that vessels like the greenbird would do better in steady winds than gusty winds. At least that was my experience when I sailed.



Ah, yes. Define DDW so narrowly that it can never be achieved because no wind is consistent enough to satisfy your definition. That is real progress!
I think it is conclusively proven that even by humber's analysis the BB travels at higher multiples of WS in a relatively low wind at closer angles to DDW than any prior land yacht. All while dragging that huge prop through the air. No small feat, even if you take humber's word.

I haven't defined DDW, but it would be nice if NALSA did if they are going to award records for doing it! But by any definition, + 30 degree and - 50 degrees is not going to cut the mustard!

 

[Llyricist]

What in the world do you find amazing about doing something that is done routinely by quite a few different types of land, ice and water yachts? What would have been amazing is if the cart did what was claimed, gone DDWFTTW but it did not do that. The record is a sham and should be retracted.

You are ignoring the part about accelerating, and increasing its acceleration, while as DDW as it is possible to get while over 2.8 X the wind speed. No other land yacht can do that.

 

[profpangloss]

You are ignoring the part about accelerating, and increasing its acceleration, while as DDW as it is possible to get while over 2.8 X the wind speed. No other land yacht can do that.

Please define "as DDW as it is possible to get". Does that include 50 degrees off?

 

[Llyricist]

I haven't defined DDW, but it would be nice if NALSA did if they are going to award records for doing it! But by any definition, + 30 degree and - 50 degrees is not going to cut the mustard!

They defined it as averaging less than 10 degrees during a ten second period, Having a speed at least .2 mph faster in the 10th second than the first.

 

[Llyricist]

Please define "as DDW as it is possible to get". Does that include 50 degrees off?

No, I am referring to the period of time it was less than 2 degrees off.

ANd why on earth do you guys keep bringing up what happened after the record was set?

 

[Llyricist]

Yachts are off topic.

LMAO, you keep claiming that's all the BB IS.... now you say it's off topic?

 

[profpangloss]

They defined it as averaging less than 10 degrees during a ten second period, Having a speed at least .2 mph faster in the 10th second than the first.

But they did not use RMS averaging. I can show you right here why that is important: Suppose the wind alternated between + 40 deg and - 30 deg during that 10 seconds. A simple average would be 10 degrees and does not represent the true wind power that was available to the cart An Rms average would be 35.35 degrees and that is a true indication of how much wind power was available to the cart the entire 10 seconds. Do you now see why RMS is important? It is not only used in electronics! If you have ever done any mechanical alignments, such as shaft runout, you will find it is the RMS average that matters. That is just one example. There are countless others.

 

[Dr. Keith]

What in the world do you find amazing about doing something that is done routinely by quite a few different types of land, ice and water yachts?

I'm trying to make sense of humbers objections, as best as I can decipher them. So far as I can tell there are no other land or ice yachts that can travel within 40 degrees of DDW at 2.8x WS where the WS is on the order of 10mph.

Further, humber has more than once "shown" that the propeller is nothing more than a drag element when over WS.

Therefore, if we take the sum of humber's arguments this cart is traveling at higher speeds so close to DDW than any comparable cart can achieve while being burdened with a 4-5meter diameter prop dragging in the wind.

Does that really sound plausible?

What would have been amazing is if the cart did what was claimed, gone DDWFTTW but it did not do that. The record is a sham and should be retracted.

The record will stand or fall on its own. I hear there is a crack analytical team working on the numbers as we speak. I'm trying to understand why humber thinks his arguments have "debunked" the BB rather than catapulting it from cool to amazing.

 

[Dr. Keith]

But they did not use RMS averaging. I can show you right here why that is important: Suppose the wind alternated between + 40 deg and - 30 deg during that 10 seconds. A simple average would be 10 degrees and does not represent the true wind power that was available to the cart An Rms average would be 35.35 degrees and that is a true indication of how much wind power was available to the cart the entire 10 seconds. Do you now see why RMS is important? It is not only used in electronics! If you have ever done any mechanical alignments, such as shaft runout, you will find it is the RMS average that matters. That is just one example. There are countless others.

Out of curiosity, what was the RMS during the test period?

 

[Llyricist]

But they did not use RMS averaging. I can show you right here why that is important: Suppose the wind alternated between + 40 deg and - 30 deg during that 10 seconds. A simple average would be 10 degrees and does not represent the true wind power that was available to the cart An Rms average would be 35.35 degrees and that is a true indication of how much wind power was available to the cart the entire 10 seconds. Do you now see why RMS is important? It is not only used in electronics! If you have ever done any mechanical alignments, such as shaft runout, you will find it is the RMS average that matters. That is just one example. There are countless others.

That doen't matter, because that did not happen. But in fact,

a. you don't need RMS to correct for that if it did. You could mean the absolute values.

b. the difference between the rms of wind direction and the rms of cart direction was only 7 degrees. They were biased in the same direction.

c. the vast majority of the "other side" peaks were caused by wind vane oscillation, not changes in wind direction. And everyone knows that. So by using either rms or abs mean, you would be measuring the magnitude of the measurement error, rather than actual wind direction.

 

[69dodge]

The opposite way to use the propeller as a turbine would be to allow it to turn in the opposite direction. That would give you the best power performance from the wind energy as I believe IRatant's videos have shown. Using a propeller to collect wind energy is dumb. I can think of few things dumber. The more directly it faces into the wind stream, the greater tendency it will have to turbine, working against the wind sail force on the cart. I mean, really, you can't see that? The further off of the direct wind stream, the less it will try to turbine. It is just a matter of finding the optimum angle off of DDW to get the best performance, but the best performance will always be worse than if you just use it as a turbine, not a propeller (LOL) This can be easily proved, and I think IRatant has already shown this convincingly. Jeez, just common sense should help you to understand this!

I don't follow. The propeller of the Blackbird doesn't face the wind; it has its "back" to the wind. Isn't that just what you're suggesting it should do?