In Reply To:
In Reply To:
You seem to trust that Tom did his best to maintain the same head position on both bikes, and I'm sure he did try, but from your comments above do I correctly interpret that you are ignoring the possibility that Tom consistently held a different head position on the two bikes? You seem to be allowing for the possibility that he moved his head around more on the P3C, but not that he consistently held his head in a different position. Please correct me if I've misinterpreted.
No, I'm not ignoring it: I specifically brought that possibility up early on. I said that if there were a change, it would have to be a consistent change, held throughout the trial: otherwise, were he shifting about (his head, or on the seat, or moving his spine or neck) it would appear as distortions in the profiles. So any putative change would had to have been held constant. But, as I pointed out in that same early response, why should Tom have hit on exactly the consistently held position change that decreased CdA from the very moment he got on the P3C? How is it that this spontaneous hypothetical change decreased his CdA rather than increasing it, and decreased it by .023 m^2?
So, we know he had great repreatability on the P2K. We know he didn't sit up on the P2K, artificially inflating its value. We know he meticulously transferred the touchpoints to the P3C. We know he used exactly the same wheels and the same PM. We know he couldn't have been squirming. We know that during the course of the test runs themselves he could not have known what the CdA was, or the effect of any positional change on CdA. We know the only equipment change was the frame. Your theory is that the lack of blinding led him to subconsciously alter his position from the moment he got on the P3C in a way that decreased his CdA by an order of magnitude greater than his usual precision.
Also, out of curiosity, what would be the magnitude of the change in CdA for Tom that could be attributed to a systematic, consistent change in head position, scapular retraction/protraction, sliding fore or aft in the saddle, and altered spinal curvatures?