Wednesday, March 2, 2016

Looking back at my trip to A2

Nearly 4 years ago (has it really been that long... geez) I loaded up my humble little Planet X Stealth and trekked over to North Carolina to get fast at A2 Wind Tunnel. Being that it's one of my most popular posts, I thought it was about time to have a look back (you know, to pad my post count) and give you my current thoughts about the time I got to spend there. Here's the link to the original thread.

First, let me preface by saying I thought I had done my research before ever laying down my credit card number. I had read as much (although, especially at the time, finding information from guys who had been, and would share anything of it with some guy asking for handouts was not very much) as I could trying to use my time as smartly as I could. I even enlisted John Cobb's (who was kind enough to take the time to help set me in the right direction.) input on what to do and what not to do. I even saved that email and think I can share it.

I would suggest not testing with the rear disc because air breaks off of them at different yaw points, they are not consistent, and it makes it hard to pin point real improvements. Wear what you are going to race in and maybe test one other outfit. Bare skin is always slower than covered skin. test helmets, turtling is OK for TT races but I find it distracting for triathlons. Test several helmets and pay attention to the "feel" of the ventilation compared to the drag. Test your water bottle placement, it is very individual.  Do a few repeat runs during the session, go back to a earlier configuration, just to be sure the tunnel data is consistent. If you have time it might be interesting to test your number location on your race belt, high vs low on your waist.  Elbow width vs comfort for swimming, 2cm can make a big difference. Have some fun, you will leave with a lot more questions as you think about it.  I do not use CdA numbers, I generally only look at drag. I do that because it is nearly impossible to figure surface area on a bike and pedaling rider in a yaw angle. If you test only at A2 then the drag will be consistent, CdA is used for different tunnel comparisons. I haven't found that you can assign a surface area number at "0" and then that be correct at a 15 degree yaw, so I look at drag and follow those trends.  There's tons of wheel data out on the net, don't waste your time testing wheels.  Position setup is a big deal so you can race with a lot of pelvic rotation, work on that but try to be realistic when testing and actually use the real position that you race with. Get somebody to snap a picture of you under power during a race and try to use that back shape, then work from there.  Have fun, learn lot's.
-John Cobb

At the time I thought I had taken his advice pretty well. Looking back, I skipped some of the most important parts, particularly the part about repeat runs. I admit, at the time I was so locked into the zone of "trying to fit it all in" that I didn't consider fitting more in was useless (or at the very least sketchy) if I didn't have repeatable results. I did re-test the final position I left with, which at least gives me a few less nightmares at night, but overall it was a sloppy use of time. John was 100% right, I left with a lot more questions as I have thought (for years) about it.

Was my time useful... absolutely. Was it optimal... not even close.
I did come out with a new, slightly more slippery position than what I arrived with, one I have used (and still use) since leaving the tunnel.

Tunnel time being used in the real world
Raising my hands was indeed a gain for me. Something many of the top fitters and aero testers pretty much universally recommend. However, from my own experiences I wonder if it is really as universally good for people who don't do their own testing as seems to be advertised. I'll share a small piece of my data from A2 to demonstrate what I mean.

Take with a grain of salt this is one man's opinion from n=1 data vs. guys who test a LOT of people, but if mine can be so particular about the exact angle of the tilt, how finicky is it for others? Also notice that at a certain point (30°, the highest I tested as it was the highest the bars would allow) going higher is not better, it's actually much worse. My data does correlate with the idea that raising hands some (from flat) is probably at least "not bad."

So... what's my opinion today, years later about going to the tunnel.

Honestly... it's save your money. You can use the Chung method (and/or Aerolab) to test to your hearts content and get good results. At least good enough to say "this helmet is better than that one." It's going to take a lot more time and work, but it is something you can do when you want without breaking the bank. The exception is if you are a die-hard numbers guy who really wants an A+ experience. I still look at my time fondly, it was a ton of fun. More fun than a week long vacation to the beach, (about the same cost...) ehh... but awesome and fun nonetheless. You are pretty well paying to save some (maybe a lot of) time and get easily repeatable (you know... if you repeat) results.

Inside (and outside) the madness of the tunnel.
Now if you found this post because you are looking to make a trip to a wind tunnel for yourself then you have my envy! Oh to be able to go back. So let me give you my advice (for what it's worth, which isn't a lot admittedly.)

- First thing, do your research. Read everything you can about it... check Slowtwitch, there are quite a few guys who have been and shared what they learned (Haycraft and TomA come to mind.) I wouldn't speak for them, but I think both would give you some good advice to maximize your time.

- Have the majority of your fit dialed in before you ever click on the website. You don't want to be figuring out your fit angles while spending $400+/hr.

- Make a plan. A detailed plan. Figure a run at 0° will take around 3 minutes, a sweep closer to 5-7. Then a few minutes to adjust something before the next run. If you have 1 hour, don't expect to schedule in 20 different runs.

- Test things in a reasonable order. It's pointless to find the best helmet for you, then change your position, because likely it changed when your position does. Imo test helmets last thing.

Don't do it in the reverse order...
- To echo John Cobb, save your time on wheels. It takes a long time to change them out and really... what are you going to learn... that 808's are better at 5° than 404's? If I could go back in time I'd have ran my race wheels in the tunnel instead of my box wheels, but it's not a huge difference.

- Verify your results and do sweeps, especially of the important things. Better to know that the things you did test are accurate and not an anomaly because you moved your head during "x" run.

Here's a link to A2's website to check it out for yourself.

Anyways, hopefully this was a little bit helpful. Always keep learning!

- Christopher Morelock

No comments:

Post a Comment