Zinger props have an airfoil shape at the tips that produces thrust, and
pulls the plane forward. The tips of the prop are moving at the highest
speed. The APC props have little or no thrust at the tips. They are designed
this way to be a "quiet" prop.

A "quiet" prop is great for quiet, but not for speed. This is why the Zinger
whoops the APC for speed.

FBD.