But doesn't that also make assumptions that one testing facility will provide more veracity of result then another without actually knowing if that is the case or even really germane? And I'll split the difference and call it 1:30, I was just doing quick math. :)

The tunnel itself is actually larger then the pic posted, in front it's another 20 feet or so for the entire structure. As I mentioned, my friend Chris is helping them create al the new software. That was the issue with this facilities previous iteration, the software was terrible, not so much the actual tunnel design considering the limitations of the space. Sure you can go to San Diego or A2 but the cost is high and there is no way to quantify the delta of results.

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-Of course it's 'effing hard, it's IRONMAN!
Team ZOOT
ZOOT, QR, Garmin, HED Wheels, Zealios, FormSwim, Precision Hydration, Rudy Project

I've been to faster a couple times (along with another) was very happy with the data......they help me get my ticket to kona punch twice now.

This topic anlong with many others put a smile on my face. Love it when the know-it-alls show what they really know.

What does that even mean?

I'm confused too...

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-Of course it's 'effing hard, it's IRONMAN!
Team ZOOT
ZOOT, QR, Garmin, HED Wheels, Zealios, FormSwim, Precision Hydration, Rudy Project

   Many post their opinions as facts.... It just shows they know less than they think they know .

well that cleared that up...

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My Blog - http://leegoocrap.blogspot.com

he is just buying that changing software fixes possible flow obstruction/restriction.

I think he was expressing his opinion.

that's a fact

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My Blog - http://leegoocrap.blogspot.com

We've seen a lot of wack test results from Faster over the years. I have a hard time believing that software is responsible; isn't it just tunnel Q and a force measurement? Operator experience and skill is surely a big factor, along with equipment accuracy and precision. The tunnel size and design is another limitation, but maybe they've learned to work around most of that? Maybe that is what the software is for.

If the consistency of flow is good (or the variations measured and accounted for) they should be capable of decent results. People generally want to know about small changes and so long as the results trend in the right direction that's probably good enough.

Yeah, my saying "software" is a bit vague. What I mean is that software was generating some odd results but that had to do with the way tests were being conducted and how the software was generating the data. Initially they had some smaller manufacturers come through with specific request for their protocol that wasn't always the most efficacious for providing accurate results. Despite warnings from the folks at Faster (previous owners) they went ahead and published that data. It was all a bit hinky if that makes a bit more sense.

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-Of course it's 'effing hard, it's IRONMAN!
Team ZOOT
ZOOT, QR, Garmin, HED Wheels, Zealios, FormSwim, Precision Hydration, Rudy Project

I think the matter of absolute accuracy vs. repeatable accuracy is something that (can) change depending on the needs / expectations of those getting the data (and what they plan to do with it)

I don't doubt that Faster can give you repeatably accurate results. So can Aerolab/Chung testing and to a lesser extent so can rolldowns or even cutting out a picture and weighing it. (in that case at least if all you cared about was frontal area)
For the vast majority of individual athletes I'd guess that what they really want when they go to a testing session is "is A better than B" and less so "what is my absolute as accurate as possible CdA." Now there are certainly times that that absolute number is much more important but probably not for your MoP/FoP triathlete.

Much like the Stages vs. other PM's discussion or Computrainer vs. Kickr/etc or even a Silca pump vs. a Blackburn... for some people, having a repeatable reading is all that is "truly" important to them... for others, accuracy matters. And in general you pay more for more accuracy.

I would guess the tunnel is plenty accurate to tell someone if the aerohead is better/worse than the Bambino etc... (repeatably) but whether your actual CdA is .235 or .228... would have to see much more in comparison.

How much does any of that matter... like most things... it depends

Ymmv

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My Blog - http://leegoocrap.blogspot.com

Yup. The only thing I would add is that you are describing the definitions of accuracy and precision. In this case accuracy would be how close your measured CdA is to the true CdA. Precision is the repeatability of the measurement. If you are interested in finding your best helmet choice, you need precision so you can figure out if helmet A is better than helmet B. Your actual CdA is probably less important for 99% of riders, though there is a cool factor with having a sub-0.2 CdA.

My guess is that many windtunnels aren't all that accurate. I seem to remember Cervelo traveling with an old P3C that served as a "tare" bike. They would use it to baseline each tunnel they visited.

I think the matter of absolute accuracy vs. repeatable accuracy is something that (can) change depending on the needs / expectations of those getting the data (and what they plan to do with it)

I don't doubt that Faster can give you repeatably accurate results. So can Aerolab/Chung testing and to a lesser extent so can rolldowns or even cutting out a picture and weighing it. (in that case at least if all you cared about was frontal area)
For the vast majority of individual athletes I'd guess that what they really want when they go to a testing session is "is A better than B" and less so "what is my absolute as accurate as possible CdA." Now there are certainly times that that absolute number is much more important but probably not for your MoP/FoP triathlete.

Much like the Stages vs. other PM's discussion or Computrainer vs. Kickr/etc or even a Silca pump vs. a Blackburn... for some people, having a repeatable reading is all that is "truly" important to them... for others, accuracy matters. And in general you pay more for more accuracy.

I would guess the tunnel is plenty accurate to tell someone if the aerohead is better/worse than the Bambino etc... (repeatably) but whether your actual CdA is .235 or .228... would have to see much more in comparison.

How much does any of that matter... like most things... it depends

Ymmv[/quote]

Yup. The only thing I would add is that you are describing the definitions of accuracy and precision. In this case accuracy would be how close your measured CdA is to the true CdA. Precision is the repeatability of the measurement. If you are interested in finding your best helmet choice, you need precision so you can figure out if helmet A is better than helmet B. Your actual CdA is probably less important for 99% of riders, though there is a cool factor with having a sub-0.2 CdA.

My guess is that many windtunnels aren't all that accurate. I seem to remember Cervelo traveling with an old P3C that served as a "tare" bike. They would use it to baseline each tunnel they visited.[/quote]

But that isn't how fluid flow works. What is being described isn't the difference between accurate and precise, but possibly the difference between accurate and arbitrary.

I don't know anything about Faster, but if the air flow of a tunnel isn't handled correctly the results won't be just skewed or scaled, they could have zero correlation with the real world.

If you really were a knew-it-all then you would know what it means.

I do. Big time.

If results are repeatable, and scale in the right direction, then accuracy is just a function of calibration.

The problem with all these "lesser" methods is either a lack of repeatability or inaccurate calibration. I'm not tunnel expert by a long shot, but this is just basic science. A tunnel like Faster's with a small test section (cross section and length) for the objects being tested, and cheap (relatively) flow control, is going to deal with some challenges. Entrance flow will be less uniform. The small cross section means that the air gets squeezed as it goes around the rider. The sharp bend at the tail means that air is disrupted before it has a chance to stabilize. And then they have abrupt changes in area and sharp corners in the test section which I don't understand; seems like they could have avoided that without much trouble.

To what degree do these things effect results, and are the errors repeatable enough to calibrate out? That's the challenging part. Wind tunnels are generally designed so that fudge factors are unnecessary, but I don't think Faster has that luxury. Maybe they've gained enough experience to account for the errors for the tests they normally do? To the satisfaction of most of their latest customers anyway.

Ron,

You may be right. I admit my only tunnel experiences are at A2, I've only ever seen pictures of Faster. (Also, while a pretty good mechanic, as an engineer I'm totally lost so I'm certainly out of my element here.)
I guess I may be showing some gullibility, but I'd have guessed it would be tough to open a "tunnel" if you couldn't get it down to at least showing repeatable results from day to day on the same setup. That would be the first thing "I" focused on nailing down, but again I don't know and I haven't seen data that proves either way.

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My Blog - http://leegoocrap.blogspot.com

While all of the noise about the Faster tunnel being accurate or inaccurate may or may not be true, it would be a mistake in my opinion to forgo a session or two there because of this speculation. I work at a place where I encounter arguments almost on a weekly basis about the scientific measurement of various phenomena. While they are usually all valid and intriguing arguments, they often magnify the overall assessment of what one is trying to generally accomplish because the pros and cons of one measurement vs another. Here is the bottom line that most here should care about: I went there, spent my money and became measurably faster as a result. I know many others that have gone there and reaped some speed as well. Carry on and continue to argue about the measurement, but don't get lost looking at leaves when all you really want is the forest.

This is the most important quote of the thread so far. For the people whose livelihood depends on aerodynamic data, you need to know that you can trust the data beyond a shadow of a doubt (bad data is worse than no data). You need to know that the tunnel flow properties are well characterized, correctable (as needed) and repeatable. You need to know that you can make tiny changes and still separate the signal from the noise. All of those things cost money and expertise, and in the wind tunnel business you absolutely get what you pay for.

If your livelihood does not depend on wind tunnel data (or, in-context here) if your position is far enough from optimal that you could just "eyeball" the improvements then even a poorly designed wind tunnel will probably give you the correct answer.

Last, it seems like nobody bothered to actually check the pricing but it seems like most people ITT have the impression FASTER is significantly cheaper. FASTER charges $450/hr (unsupported), while A2 charges $495/hr. For a supported test FASTER charges $600, while A2 charges $545. If you're bringing your own mechanic then this is a moot point (and I have only been to A2 so I can't say for sure what level of support you get for your money at FASTER), but I wouldn't bother booking tunnel time without planning to have some extra hands around for model changes. That being the case, A2 actually comes out cheaper.

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I tweet!

With the exchange rates it could actually work out cheaper to fly to the UK for an AeroCoach session in the velodrome...

Hi Jens - yeah, I had to check my database to help stoke my memory of your test. Looks like you tested with multisports.com and I was just starting out working with them at that time. Crazy to think that you tested in San Diego in 2005! Many things changed as I got more comfortable and ingrained in the workflow.

I don't really have a dog in the tunnel fight anymore - though, the folks and facility in San Diego will always be my favorites. I have some good tunnel stories to tell from the years there...if you are ever in town give me a ring and we can go for a run or ride and maybe you'll be able to tolerate them! :-)

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Kraig Willett
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Waiting for my final data but here is a video of my last run.

Jesus the technology has f that s forum sucks..I'll post when I'm not on a phone.

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-Of course it's 'effing hard, it's IRONMAN!
Team ZOOT
ZOOT, QR, Garmin, HED Wheels, Zealios, FormSwim, Precision Hydration, Rudy Project