How to use Aerolab?

[wacomme]

I did some aero testing today. I put the data into Aerolab thinking it would be intuitive to figure out, but I'm confused. How do I calculate CdA? The wiki link for instructions I see online doesn't seem to work. 

What am I supposed to do with the sliders, and which ones? What's the goal in matching up the virtual and actual elevation lines? Do I use time or distance? My data isn't great since there was wind, but I'm looking for ballpark CdA estimates. Lines seems to come today at both 0.2 and 0.6 CdA. Which is correct, if any? Even some basic instructions would be most useful.

[wacomme]

I can't seem to be able to upload the .fit file. Darn.

[wacomme]

Here is a screen shot. Is this correct?

[Robert Chung]

On Sunday, March 3, 2013 4:42:04 PM UTC-8, wacomme wrote:

Here is a screen shot. Is this correct?

Slide the CdA slider left or right until the VE line is about on top of the "true" elevation line. That will be close to your CdA. In this case, the VE line is above the measured elevation line so you'll have to slide the slider to the right, raising CdA. As you get more experience, you'll be able to narrow in on the right value of Crr but for now just leave it at somewhere around .005. That is often the right ballpark.

If the wind wasn't howling, and you were in a TT position, you'll probably be able to get the VE and "true" elevation lines to match up somewhere in the .2 to .27 m^2 range, depending on how aero you are. If you were on a road bike in the drops, probably something like .25 - .35 m^2. If you were on a road bike in the hoods, maybe .3 to .4 m^2. If it's a cold day and you're bundled up and wearing tights and a long sleeve heavy jersey on your winter bike, you could be somewhere between .35 and .5 m^2. If you're riding a MTB in a pretty upright position, maybe .4 m^2 on up.

[wacomme]

Thank you. 

[Robert Chung]

Ideally, you'll want calm conditions (both in terms of wind and traffic) but here's a quickie test you can do just to get a handle on what to do. Try to find a loop without stop signs, or an out-and-back with maybe a little dip or something in the middle. Make sure you won't get hit by a car and have good sight lines. I just go around my block a few times. Do a loop in the drops, then another loop faster, then a loop slower; then repeat with your hands on the hoods.

Weigh yourself and the bike and ballpark the air density.

See whether you can come close to modeling the "true" elevation profile by sliding the CdA slider around. Even with this informal test, as long as the wind isn't blowing too hard, you ought to be able to see a difference between the loops where you were in the drops and the loops where you on the hoods, and to spot little bumps and dips in the road.

[wacomme]

Thanks. I used a high school parking lot on Sunday. The wind was blowing so the elevation lines don't match up well, but I can see differences between road and tt bike, hoods and drops, and even regular vs aero helmet. This was my first attempt. A student of mine (I'm a teacher) is using this experiment as part of his 10th grade Personal Project for the International Baccalaureate program. It's a good learning experience and should make an excellent Personal Project.

[Robert Chung]

Damn, I'm jealous. I was trying to get my daughter to do this for a science project but she doesn't take anything I say seriously.

You can certainly use a parking lot but a far more consequential choice is finding a spot sheltered from wind and traffic. That is, in traditional aero testing with a power meter, you look for a venue that's flat and wind- and traffic-free. This approach removes the flatness constraint. It also means that you can "anchor" runs by features on the course -- you can spot dips like storm drains and crossing the crown of a road. A student who doesn't have access to a power meter can also do coast downs; it's more hassle but it's possible to do if you have a way to record second-by-second speed (in a coastdown, power is zero, of course).

[wacomme]

To meet assignment deadlines, we have to use the data collected last Sunday. Wind will certainly be the major error in the experiment. We now need to interpret the data, explain it, and create a website for the project.

Later this year I'll do my own testing with me as the subject and different aero parameters. I'll pick a windless day and improve upon the errors from Sunday.

[Robert Chung]

On Tuesday, March 5, 2013 1:51:27 PM UTC-8, wacomme wrote:

To meet assignment deadlines, we have to use the data collected last Sunday. Wind will certainly be the major error in the experiment. We now need to interpret the data, explain it, and create a website for the project.

Later this year I'll do my own testing with me as the subject and different aero parameters. I'll pick a windless day and improve upon the errors from Sunday.

1. http://www.youtube.com/watch?v=b8tJnFE_BFg&feature=youtu.be&t=27m58s

2. Have the student cut out a couple of rectangles of cardboard of the right size so people can visualize CdA in m^2.

[wacomme]

Thank you. I'm passing these suggestions on to the student.