sleazy

just figured i'd share a few thoughts-


first- the CPT in Colorado is a rip off.

now- that being said, let me state that i've never been to their facility. but from the level of service, feedback and price of what was delivered to me by the A2WT tunnel in Mooresville, NC this friday... for UNDER HALF THE PRICE of CPT... i hold by my claim.

story- i had the means and the effort ready to fly out to Colorado. i had time reserved and was about to book plane tickets when they had to shut down for a period of months, effectively canceling my reservation and my window of opportuntiy. so, i was all ready to give them my money for what i perceived to be the highest level of serivce. with my time/window shot to he!!, i went looking elsewhere and found the A2WT.

whereas the CPT charges $1695 for a session ($1350 per hour + $300 for 'position optimization')... i did close to 20 exact measuring runs, was in the tunnel with power feedback for over 2 1/2 hours and could ask any and all questions... for $700. (my DVD with all postions (side, front and top) and their corresponding data is being mailed to me so i dont have any fancy shmancy pictures to post... yet)

so, come out of the woodwork and tell me i'm wrong... but i hold by my claim, that the CPT cant be twice as good.


second- its all in the body

these forums get so overwhelmed by "should i have an Bontr aero bottle or an Campy aero bottle?" when in reality- almost anything on a bike is borderline negligible. however- move your arms 2 inches... turtle your head half an inch, drop your shoulders an inch... and holy cow! can you get some great results.


third- you can get close- but you cant do it on your own

when i showed up, my base line was termed 'higher end of average'. flat back, high seat, slammed bars, funny helmet, et al. however, we started moving my arms in from their current position. the Cda numbers went up (bad) every half inch i moved them in--- until they hit a sweet spot and dropped drastically. the overall postion, you can get get close to- by studying pictures, posting here (a la PCAD) but to make it come together and work as a unit- there is no road-test way to get this sort of feedback.

fourth- no one thing works for different people

at the end we tried some different helmets. my LG, an LAS, a SPIUK, the GIRO and a visored Limar. they all had different contours along my back, and different contributions to my CDa. so for someone to ask- "is the X best?" - there is no blanket answer as to what is good or bad.

fifth- surface area is good

seems that the more surface area you have- the better the sail effect with any wind angle greater than head-on. disk is better than tri spoke is better than spoked aero rim is better than spoked box section. the determining factor is how difficul to control it is.

...

so, go out and look at your rig. ask yourself how much did you spend on those wheels? that frame? that helmet, skinsuit, cleats and bootie-cover ensemble?

for a fraction of any of the above expendatures- you can have a really neat experience that ties together the whole system and really hands you WATTS. my numbers showed that i gained 24 watts in aero efficiency... what set of $700 wheels or frame can do that?!


anybody on the eastern seaboard- or anyone that wants the experience but doesnt want to fork out for the CPT... look to the A2WT. you'll be glad you did.



all right, as this is BF- let the bashing begin....

ElJamoquio

More great feedback on windtunnels... hmm., I might be going to NC this spring anyway for a pseudo-training-camp...

sleazy

man, if you are there anyway- go ahead and do it. it'll be the best money on TT equipment you'll ever spend.

somehow- having an AFFORDABLE wind tunnel that you dont have to fly to Colorado for- kind of takes the stigma out of it.

pjcampbell

I did my first real TT the other week and really dug it. That is to say one where aero really mattered a lot.

I kind of had that feeling that people can tell you what works for them but nothing is going to tell it for you like the wind tunnel. 24 watts, that is a lot. Especially if you gave up no watts to get those watts.

DrWJODonnell

bashing. First, CO has the USAC discount. My whole trip amounted to $1400 and that was with air, hotel, and meals. The data and people were excellent. However, I will say that more recently, my coach went to A2 and likes it atvleast as much and it is cheap. Yes wind tunnels are good. Yours sounds like a great experience and I honestly will probably go in the offseason. I just would hate to say only one is great. I have heard good things about San diego and Texas as well. Bottom line, it will help.

waterrockets 

Good report, looking forward to more. I'm starting to eyeball the ANT+ Sport PT upgrade with an ibike... Probably $700 total, and you have a mobile wind tunnel whenever you need it. From what I've read in the wattage forum, it's about as accurate and precise as a wind tunnel.

CastIron

Do tell.

asgelle

How do control for yaw, though?

simplyred

Thanks for sharing the experience.

waterrockets 

I don't have any of the threads bookmarked, but a wattage group search for "ibike aero" turns up most of the related threads.

ibike covers it a bit here too.

Good point, all you would know is how much drag you have, not what wind angle got you there.

To do this testing, you'd want a mobile weather station anyway (so that adds $50), so you could record that data before, in the middle, and at the end of the testing period.

Pedaleur

Note to self: build wind tunnel in the garage in my spare time...

The ibike thing looks pretty slick. I'm assuming we'll get a full report from you, wr?

waterrockets 

I'd probably want to get a TT bike first

I'll be happy to offer critical commentary on the experiences of others though.

sleazy

i wrote the original bit last night after i got home from my trip... so here's another point that i forgot...

six- Roadies benefit more than Triathletes

i didnt necessarily think of this, this point came from the technician. he said that with roadies, he can shape their positions more drastically than triathletes. a triathlete is usually set up wider, less back slope, head more up... because they still have to run when they get off, and in an ironman case- are on the bike much longer. a TT guy- usually falls over and pukes when he crosses the line- leaving it all on the course. he can endure a more severe position for the alotted time. i just assumed that TT and tri guys were treated the same and found the difference interesting.

sleazy

the DVD just showed up. here's the data-

when i started, i had a cDa of 2.524- when i finished, it was 2.262

test speed was 29.34mph as per the computrainer. my initial base line showed 276 aero watts to hold that speed. my finalized position required 251 watts to hold that. a theoretical gain of 25 watts.

for a NACA standard day- sea level, standard temp and humidity, and a test speed of 30mph (NACA standard)- my base line was 341 watts, new position would require 311 watts.


they sent me every second of video and every still they took. again, i'm quite impressed with these guys.

ElJamoquio

Define your 'A' - i.e., your units - those numbers seem high, perhaps they're in ft-squared.

And holy jeebus, how small are you? There's no way in hell I can hold 30 MPH.

waterrockets 

yeah at that speed, I'm looking at 380W

Racer Ex 

Oranges suck. Never had one, but I had an apple and it was half the price.

asgelle

Though once again the question of yaw angle comes up. These are single numbers. Are they for a single yaw or some average over some range, and how were the particular angles determined? This stuff matters. A lot.

JPradun

Can you send me the video/pics of what they did? I'm curious to know how much more it entails than what I imagine.

Thanks

sleazy

yaw- almost all runs were done head on. the initial base line was run at 0, 5, and 15 degrees.

after all the testing was done, the race position was also done at 0, 5, and 15.

the numbers quoted above were only for head on. the cDa dropped quite a bit more with anything off center (that sail effect mentioned above).

the A used in the equation was not directly measured. to do that- you'd have to take a head on picture- overlay a calibrated grid and count squares to give you an individualized, 2D surface area.

instead, they use an already accepted value of 3.39. this, i was told, was a meaurement that actually gets factored out.

as for the exact watts and speed numbers- i think its all relative. what you are looking for is the difference between your start and finish numbers.

carpediemracing 

Thanks for a very informative write up. I went to some seminar where a bike manufacturer talked about aero set up - essentially they said that the rider was the biggest factor, and that for their "normal" guy, the aero helmet was best, but the guy with no neck (one of their own) a poorly ventilated standard helmet worked better.

Your post reminded me of that. And to drop 25 watts and hold the same speed, that's really substantial.

I wonder if they do sprinting tests

cdr

DrWJODonnell

they do sprinting positions and yes, A2 does CdA in square feet, not metric for some reason.

Bantam

DrW, do you have a flickr account or some place where you have photos of your TT setup?

fly:yes/land:no

did you ever figure out what yaw angles to go with? last time i remember this discussion, it seemed like the weighted average was the best way to measure (scientific graphical representation: _/\_ ), but there was some debate over what yaw angle is most common in real life conditions. basically, how to graph the curve. iirc, the greater the average yaw angle, the more important wheels become.

asgelle

That's a problem for people much more involved in the subject than I am; but if I were going to a wind tunnel, I would spend as much time as I could trying to figure out the likely wind angles for the key events I was targeting so the testing could include those. The protocol described here sounds like they only optimized position for a direct headwind (an extremely rare condition) and then just measured drag at a few angles at the end. From everything I've seen, though, there's good reason to believe that this position at 0 degrees will not produce the lowest drag at off-axis wind angles.