Aero testing....confused by result

[matthew.weigel]

@SomeCallMeTim

but how often do we have the wind blowing head-on, as opposed to every other possible angle?

The effective angle of the wind is the sum of two vectors: how the wind is actually moving and how you approach / move through it. If you’re moving at 30+km/h, then the biggest component is that self-made headwind.