Wednesday, July 24, 2013

A2 Wind Tunnel

Alright, this one may take a while (but don't all good things?)

I am not sure when I got my first vicarious taste of all the goodness the wind tunnel has to offer, but I can say for sure that when Tim Ferguson went earlier this year it truly wet my whistle. There are few things that prompt more nerdgasms than free speed on the bike.  I don't just do certain things because I want to be faster, however, I do them because I LOVE bike stuff.  This new gadget, that new toy, that new bottle, etc.  You know the drill.  If you're reading this then you have a pretty good idea about how hard I geek out about new stuff.  So the prospect of going to something that has become the pinnacle of discerning triathletes and time trialists really revs my engines.

I had another little tease a couple of months ago when I went up there with Cid Cardoso Jr who was helping out an Inside Out Customer and I got to see, more specifically, the dynamic of what happens when you are testing and doing runs.  It helped me get a better idea of what I myself would want to test should I ever get up the gumption to plop down the dollar bills for a trip myself.  Last, but certainly not least, I got to go last Monday to help Dave with a media experiment that has yet to be published so I cannot really discuss it in detail but, suffice it to say, is pretty darn cool.

The whole entire point of going to the wind tunnel is to separate the wheat from the chaff, or more generally eliminating the vagaries of the so-called "eyeball aero tunnel."  Some things "look" faster but are not. Some things "logically" should make you faster, but they do not.  The testing in the tunnel eliminates those question marks.

Which helmet is better?
Is narrower always faster?
Is lower always faster?
Does saddle height affect frontal area?
Does head position matter that much?
Does hand position matter that much?


I remember discussing with Bill Robertson - a fellow AC3 athlete - what a trip to the tunnel would really MEAN.  On one hand, you have the possibility of gaining all of this unknown amount of speed through no increase in fitness and on the other hand you have the possibility that you will not.  Both are positives in the sense that if you experience the latter, if nothing else it is justification that your choices made up to that point were good and right and aero.  There is low-hanging fruit of the aero world, then there is fruit that is kind of high up in the tree and tougher to get to.  Once you've snagged all that low, easy fruit, your job gets much harder.

So on Monday morning of this week I rolled up to the A2 base of operations up in the middle of nowhere Mooresville, NC and began to figure out what was really up with aero-ness.

Step 1 in aero testing is to establish a baseline from which the rest of the runs will be deemed "successful" or not. This is pretty much what I had to work with for my baseline:

My bike was setup with 2cm of "aero-matched" Aduro spacers under the stem, a certain saddle height of let's say "X," and that was pretty much it.  I decided to test in my tri suit versus my speedsuit and TT kit so I could ascertain a more triathlon specific baseline and know that if anything I could improve slightly upon that with the better/faster apparel I'd use in a TT.

I didn't see any of these results until after the fact so my only frame of reference during each run was whether they'd run the test at 10 degrees of yaw or not as that signified that they wanted to verify the improvements at zero degrees.  This first test/baesline was run at 0, then at 10, then back at 0 to verify and provide a control.  My input speed was 25mph as that is roughly what I will average in a half-ironman (plus or minus a few, obiously) and "aero watts" are the frame of reference for improvements.  Aero watts is purely a measurement based on aerodynamic/CdA alone and does not factor in rolling resistance, drivetrain loss, etc.  So it takes more than those displayed watts to go the intended mph (dang, right?).  Another thing to keep in mind is that modern TT/triathlon bikes will ALWAYS be better at yaw than at 0, especially when they have aerodynamic wheelsets installed.  The "sail" effect provided by the aero shapes greatly benefits the modern rider.

The second test I ran simply changed the hand positions to a more Dave Zabrieski like style of one hand wrapped over the other.  This changed my elbow position and affected my reach a little bit but it is something I do when I am on a long, flat straightaway or downhill where all-out power is not required.

So at 25mph the gains were not much but if you increase the input speed to 29 mph (or 30, the speed at which most companies report results because of the greater statistical difference) the gains are slightly increased.

The next run put my hands back to their "normal" position and moved the pads in 1cm on each side (or, as narrow as the stock 3T Aduro elbow pads will go).  This result showed a more marked improvement over the hand position change.

You can see that Dave also tested that position out to yaw to verify that it was an improvement (although it showed no improvement at yaw, which is not actually surprising).  Jim O'brian also wanted to test wider, hence the 4th run which showed a dramatic INCREASE in watts required so that one was eliminated right away.

The next three tests lowered the bars 10mm, then raised the saddle 10mm, then lowered the bars another 10mm (so the bars were "slammed" onto the frame).  The first of those was a natural extension of testing, to see if lower did indeed net a faster position.  As was the third of those three runs.  The middle run, or the run where my saddle was raised, was deemed necessary as it was fairly clear in the video to Brian, Heath and Jim that my saddle was a little low.  I don't know Jim that well other than his reputation and history with bikes (it's long!) but I DO know Brian very well and Heath and trust their opinions on this matter and they both said it needed to come up, so it did.  Now, the slightly annoying part about this necessity is that it increased my frontal area, which resulted in more grams of drag.  Dang! So Run #6 essentially became the "new baseline," something to keep in mind as you continue reading! (so exciting, right!!!)

As you can see from run #7, 2cm lower than "baseline" (from an armpad stack standpoint) was indeed faster but it was not comfortable to me.  It is something I could probably get used to but that is not something I will implement right away as I think the bike would need a little more reach as well (it is currently maxed out on reach) to aid adaptation to the lower position.  So while run #7 was the fastest of the day to that point I requested switching back to baseline 1cm of armpad stack, +1cm of saddle height, -1cm of armpad width.  So that became the new comparison (run #6).

After all that, I had actually LOST watts compared to the original baseline.  But the fit itself was better due to the more natural saddle height and the other improvements kept me close enough to almost be within the margin of error anyway.  So moving along it was time to test different helmets.  I own both the LG Rocket, which I had been using as the baseline because Kask has yet to supply my helmet with the proper CPSC sticker so it is therefore illegal for me to use in triathlons (although it only gets checked in races with a pro field).  But still, testing the Kask would be worth it.  I tested three basic positions with the Kask: head "normal," chin "down," and head "normal" plus the hands wrapped over each other.

Head "normal"

Head "lower"

Head normal + hands high

So remembering that the "new baseline" was 191 watts at 0 you can see that the Kask was only faster in one position, run #11.  The position in that one is not particularly sustainable for long periods of time as power output becomes an issue with the hands held as they are in that third photo.  Anytime the helmet looks down it appears to get worse (a lot worse, which is surprising considering it's shape).  Moving along I tested another three helmets: the Giro Selector (tests faster pretty frequently), the Giro Advantage 2 (an old design from Giro) and the Bell Javelin (very similar to the Selector).  The third was much worse so I won't even post those results but the other two were interesting.

Giro Selector

Giro Advantage 2

The differences are fairly clear between these two helmets and the LG.  Remember that the "new" baseline at 0 is 191 watts with the higher saddle so using that knowledge the Selector represents a very slight improvement but more surprisingly the Advantage 2 represents a marked improvement even at "just" 25mph (the difference goes up more dramatically at 30mph).  This is a pretty old-school helmet that even the Giro-sponsored pros no longer use.  Be that as it may, the numbers don't lie and it may be worth switching to this helmet in the future.

The last two tests were of one more helmet, the Specialized TT02 (which was much worse so won't post those results) and the true "turtling" head position.  Now, a true turtle is pretty difficult to manage and requires a great deal of practice.  Pulling your shoulder blades together as closely as possible and holding your head tucked very low is difficult to pull off for more than minutes at a time.  In fact, when they did this run by the end of it (say roughly 3.5-4 minutes of continuous holding of the position) I was dead tired from it and decided I couldn't do any more tests (6hrs of riding the day before probably didn't help...).  But the results were quite telling...

Can he see up the road?? Sort of...
Head lower than back? Check.

Arms and shoulders visibly straining to hold the position? Check.

That position represents a fairly noticeable improvement in aero watts, subtracting 8 from the 191 the "normal" head position required.  This is, however, the only position at which I felt as though I would be unable to sustain for longer than a short period of time.  Every other run I held a "realistic" head position as I felt that it was representative of what I would do in a triathlon.  The takeaway from this particular run, however, was that in certain situations (i.e. the back and front stretch at Lowe's 10mi TT) it is definitely worth it to concentrate on body awareness and head position.  At 30mph the gains are far more noticeable: 191 to 183 at 25mph and 329 to 316 at 30mph; so a big difference!

That pretty much completes my testing.  In an ideal world I would've liked taken two or three more runs to test TT apparel (swap trisuit for skinsuit, tri shoes for socks + shoes + booties) and hydration/storage (BTA bottle, bento box, rear Xlab mount) and see what kind of gains and losses those elicited but I was pretty tired and didn't have much more consistency left in me at that point.  Plus, it's really expensive.

My takeaway is just that there was simply not that much room for improvement, which didn't really surprise me.  My watts to mph equation has always been one of the best among people I've spoken with so to see that validated in the tunnel was certainly confidence inspiring.  It was an extremely awesome opportunity and the data will prove to be very useful when it comes to equipment selection and choices in the future.  But ultimately it was VERY clear that it is an incredibly individual thing and that what works for me will almost certainly not probably work for you.  I'm not even sure I could say that there are general trends one can follow as that would do a disservice to science and provide unnecessary encouragement to the eyeball aero experts that are out there.  Sometimes they are right and sometimes they are wrong.

If you need to choose a helmet here is what your decision process should be if you are unable to go to the tunnel:

Step 1) Pick a cool looking model
Step 2) Verify size
Step 3) Submit payment

Because there's no other way to know which one is going to be "better" or "worse." It seems as though, with me anyway, lower did get faster and narrower was also faster, albeit not by much and being much lower would be uncomfortable at this point.

I may or may not think of other tidbits to add to this point but to sum it up I can think of one word in particular: enlightening.

Ask any questions you want!


Nick said...

So awesome James; I thoroughly enjoyed this!

Terry Slifer said...

great feedback and analysis. I thought you did a great job of explain the parameters of the test but more specifically the "feel" quotient. while some positions etc were faster, they may not be realistic. great job