Expected CdA Precision

[nikshar]

I'm curious about the kind of precision other users are seeing in their CdA testing. I've read of +-0.002 in a couple of places in this forum, but haven't seen the data that goes with it - I'm more interested in understanding all the different parameters that went with such precision.

The best I'm seeing (when my test route had 0 cars/bikes interference but had some non-gusty tail/head-winds, with a 4.5 minute out-back loop) is around +-0.005 for the 95% confidence interval. Which, roughly speaking, makes it so that I can't really tell apart configurations that are at 10-15 W of difference.

Today I tested the difference between raising my stack height by 6cm. The analyzed CdA values I got for baseline were 0.185, 0.181, 0.171, 0.172, 0.178, 0.178 and that for the higher stack height were 0.178, 0.180, 0.171, 0.175.