Originally Posted by
Racing Dan
To calculate power to hover or sail forward in a Uboat or cycle forward (not account for rolling resistance), in all cases you relative speed to air or water.
Actually that is how you calculate the
force of air drag. It is proportional to s**2, where s = the relative wind speed = u + v, where u = wind speed and v = rider speed, in the simple case of a direct headwind.
The
power requirement to overcome that force is proportional to s**2 x v, where the rider speed, v, is simply the rider’s speed over the riding surface.
If you refer back to Brandt’s article, the variable names are different but the calculation is the same. Drag force = D and is proportional to W ** 2, where W is the relative wind speed and the power requirement, P is proportional to U x W **2, where U is the rider speed (relative to riding surface.).
Otto