It's been impossible to do much testing in the past two months due to weather. I can't get out there in a skinsuit if the temp is below 55 degrees - it's just too uncomfortable. And any breeze at all invalidates the data; so that eliminates lots of days.
But yesterday I was able to get another set of data collected on my P2K. So now I have three data sets with the same setup. My CdA results from three different days on the same test course are 0.228, 0.230, and 0.235. Based on n=3, my average CdA is 0.231 and the standard deviation is 0.0036. These numbers reflect skinsuit, TT helmet, shoe covers, no gloves, Zipp 303 front wheel, and power tap with Kinlin XR-300 (30mm) rear wheel.
My Cervelo P2K frame was slightly damaged in a crash last year, so I'm about to move my P2K components over to a Cervelo P3 frame a teammate recently gave me. I'll set it up exactly the same as my P2K, except I'll run a Zipp 404 on the front instead of a Zipp 303. The only difference between the new test setup and race setup will be the absence of my disc wheel during testing.
These aren't my bikes, but depict my old P2K frame and new P3 frame:
I'll be interested to see how much difference the frame change and 303 vs 404 change make to my CdA.
5 Comments:
are you looking for predictions in the change of Cda?
;)
g
Oooh! Oooh! I have a guess!
I wasn't fishing for guesses, but sure - throw me some numbers.
I'll guess replacing 303 with 404 front and changeing from P2K to P3 wont' make much difference. I'll guess CdA will improve from 0.231 to 0.225. If that's the case, it may be hard to see in my testing.
Sorry for being cryptic. I'm guessing Greg and I were both referring to this thread:
http://forum.slowtwitch.com/cgi-bin/gforum.cgi?do=post_view_flat;post=1802183;page=1
The thread is long but the first post really covers it.
Wow - that's almost exactly what I'm doing. But I find it hard to believe I'll see as much change in CdA as he did. I'm thinking other unnoticed changes in his position must have come into play to lower CdA that much. It does have me intrigued, though.
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