Another aero weenie tidbit (David Warden tests)

William Jenks

David Warden of tri-talk notoriety has done some wind tunnel work recently and has been publishing the results on his site for his Tri sales company (PowerTri.com...and yes, btw, I've ordered a few things from them over the years, and they have given me good service.)

The latest missive is on aero effects of clothing.  Even given the caveats (0 degrees yaw being an important one), his data are remarkable.  I can't say I'm sure I believe them entirely...it just seems like too large an effect for such similar clothing... but it's worth having a look at.

http://www.powertri-blog.com/biking/preliminary-wind-tunnel-results-on-apparell.html

Al Truscott

I simply can not believe my De Soto Forza suit, various versions of which I've worn since 2004, has been costing me 10-15 minutes on the IM bike leg. Wind tunnel schmind tunnel. I want real world data. OTOH, I never would have believed shoe weight could make 20+ seconds/mile difference until I tested them for myself.

On another front, when is he going to test shaved versus smooth legs to answer THAT question - much more important, I would think.

William Jenks

Even more remarkable is that one brand of calf-covers would be so beneficial with the other being deleterious.

Maybe you should shave one leg and see if you start having to steer away from that side. :-)

tgarson

Even though I love Tri Talk and am often impressed with the thoroughness of Dave's tests, I just can't buy this one. This seems far more illuminating to me on the topic of the dangers of margins of error and interpolation than the topic of aerodynamic garmet performance.



But I could be wrong, wouldn't be the first time.

William Jenks

I'm with you. In the comments section of a previous post of his, I tried to push him on error bars and uncertainty extrapolation. He did have a sensible data rejection limit, but never came through with uncertainties.

tuckerm

Posted By Al Truscott on 01 Mar 2011 02:57 PM

I simply can not believe my De Soto Forza suit, various versions of which I've worn since 2004, has been costing me 10-15 minutes on the IM bike leg. Wind tunnel schmind tunnel. I want real world data. OTOH, I never would have believed shoe weight could make 20+ seconds/mile difference until I tested them for myself.

On another front, when is he going to test shaved versus smooth legs to answer THAT question - much more important, I would think.

 

Rich has been trying to get you into some EN kit Al, maybe this is the last push you need!

Like Trevor I am somewhat skeptical of these results.  Though I am amazed at how the differences in apparel can be so huge.

Al Truscott

Yep, Tucker, I'm going to give it a go at IM CDA. I'll be there in my 2 piece EN Red, White, & Navy Blue. Who knows? Maybe I'll make up on the bike the 10 minutes I might lose on the swim from last year's time (based on the TT I did last Sunday)?

tuckerm

Cool Al, so I will be there for the inaugural wearing of the EN kit. Swimming? What's that? Thanks for the gentle reminder that I need to you know, actually get in the pool.

mgraffeo

It's for discussions like this that I've given serious thought to buying an ibike aero and combining it with a wireless PT to offer local wind tunnel testing without the tunnel...

tgarson

Mike,

I agree with you there, especially after reading Wattage about all of the various 'chung on a stick' and other CdA measurement approaches. I'd love to be able to tune my bike fit and perhaps eventually tackle other issues like this.

gilliatt

I am curious how well his gear fit him. I've never wore the desoto stuff as tight as I have last years EN tri top. IIRC some of the MIT wind tunnel stuff said a bib number that flapped makes quite a difference. Curious to see what else he comes up w/

William Jenks

Yeah, of all things, that whole number business (on the bike) seems like a very simple thing that there ought to be some "good answer" for but I don't know what it is. For real TT's around here, I've seen people spray-glue them onto their shirts on the back. Obviously that doesn't quite fly here.

kurshing

Maybe the ONE real take-away here is that, in considering which things to include on our bikes and our persons (clothing, shoes, wheels, water bottle placement, etc.), it is the sum total of a bunch of little decisions which makes an overall significant impact on our drag. It may NOT be one piece of equipment that is so important...just all of the equipment.

gilliatt

@William there is a way to cinch it up on a belt, (someone nemo? posted a pic a long time ago circa 2009?). Then I stuff it in the back of my bike shorts that way it is partially visible. That is as good as I can come up w/.

mancona

@Stephen - great piont, I fully agree with you

@Dan - I do the same, fold it under race belt once and then tuck into my shorts. Not perfect but definitely better than flapping all over the place making a ton of noise. I believe Macca decided did not wear his number in Kona ... seems to have worked out ok for him. I think race numbers should not be required anymore, body marking and a chip should be good enough. Have the chip marked with the number as well and if the offical can't red the numbers on your body markings, bike helmet, or bike frame, then have them stop you to check your chip.

mgraffeo

Everybody's gotta wear the number, so...

kurshing

Has there been a study that compared the aero bottle vs. the torpedo mount (xLab)? I would be interested in seeinng that...knowing that the action of drinking with the torpedo mount would actually be slower than with the aero bottle.

William Jenks

Same site, you can see his data on water systems.

You can do a torpedo mount with zip ties, which are a lot cheaper than the xLab. ;-)

The action of drinking itself is of course slower, but you are drinking so little of the time that it's irrelevant. If the business about the straw is right, you're better off sitting up a bit now and again to drink from a torpedo mount. But there's always that "availability advantage" of the aero drinks to account for.

kurshing

@William...thanks, i simply didnt notice the torpedo mount, just an oversight. Also, you mention availability; i am torn on that because when it is readily available, i tend to blow through water really quickly, often more quickly than i need to. On the other hand, i am thinking with this torpedo mount that i may not have that issue. However, I have not done a long ride with this mount, and, i also don't want to swing so far in the other direction that i don't take enough in...I will have to see how it turns out.

William Jenks

Yeah, practice on some rides is the way to go. Even if you decide to buy the XLab doo-hickey, you can always just do the zip tie thing to try it for a while.

kurshing

@William - one more question (well, at least that is the plan): how significant is the 0 yaw factor in his experiment? In other words, if i was contemplating running my Torpedo mount (I had someone give me this for Christmas, because, yeah, it IS expensive!) and a down tube bottle for my hydration for IM CdA this year, is this study significant enough that I SHOULD be swayed to going back to my aero bottle up front and my xLab 2-bottle set up in back?

It sounds like you have a more scientific mind than me...I am a financial planner who is bad at math - go figure!

Thanks!

William Jenks

I don't find these data persuasive enough to make big changes.  In fact I find them very frustrating as an experimentalist.  Here are a few reasons:

• The yaw issue.  Would something like 8-10 degrees yaw have been a better choice for a single angle?
• The fact that all of this is pretty tied up in the individual and his/her fit as well.  That means you might just be guessing wrong.  If you have a certain front end, it might be that the aero drink had different effects...same for how the torpedo mount fits behind your fists and between your arms.
• The fact that we don't know anything about the error limits
• The fact that small changes made huge differences in his data...for example see the rear hydration with and without the CO2 cartridges.  Not saying that is NOT real...but you'd really want to see that kind of thing duplicated.  Same thing for the two brands of calf covers...very counterintuitive.  (I don't know what the fabric is like, but wow!)

I'm a two-bottle guy.  One up front - either torpedo or aero, and one on my frame on the down tube with nutrition.  I haven't spent the money for an aero bottle down below, but I may this year.  Pisses me off to be asked for $50 or whatever for a water bottle!

tuckerm

IIRC Warden says they are going to do further tests with more yaw angles. One would have to question why they would do all of these tests with only one yaw angle. They did tests on helmets, hydration and clothing. Why not just focus on one category and do a more thorough job? I get tunnel time costs some money but it seems like they were planning multiple trips from the start. And also, Warden even says that the tests are not complete and could be filled with errors. Why release the "data" then? Web traffic?

William Jenks

I'm obviously speculating, too...

But I imagine it's because he doesn't how how much more he's really going to get to do. He's part of that Joe Friel, high dollar coaching universe, but if wind tunnels are still a couple grand a day, it's still a lot of money.

I totally respect his curiosity for several variables and wanting to get some real data. It's just frustrating how it doesn't all add up in a simple way. A lot of scientists will put out "preliminary results" before a full paper too (e.g., a bunch of tests all at one yaw instead of several), but usually there would be a better set of controls.

kurshing

@William - well, if you're rolling with the 2 bottle set up too, I guess I am good with that. I also have my bento box behind my front stem and I am trying to figure out how/where to carry my spare tube and CO2. I have it on an xLad behind the seat kit (with no bottle cages) at the moment, just to keep it out of my way during my training. Not sure what to do with it though.

Yeah, I will just brush this study off as no completely reliable at this point...the sock thing blew my mind too! That just seems unreasonable.

You mentioned the aero bottle for your downtube...I thought about that but decided against it because it can't really be refilled during a race (I am focused on IM this year).

Maybe I will post a pic of my rig and see if anyone has ideas as to what I could do with it to speed it up...

William Jenks

@Stephen - A lot of people use their downtube bottle for calories (Infinit, Hammer, Gatorade, whatever) and their upper bottle water. If you are carrying your own nutrition exclusively, then you don't need to refill that bottle (e.g., if you're doing a HIM, it's pretty easy to put 500 cal in a bottle). Some people will put half of their calories in one bottle and pick up another one at special needs. But if you don't want to stop at all or if you're going to live off the course entirely, you're right that an aero bottle on the down tube won't work unless it's something like a Speedfil.