The first source is the ball itself. Though we tried to launch the ball with
the same starting orientation for each test, we noticed slight variations in the ball’s orientation
each time it exited our launcher. The Teamgeist ball’s surface comprises 14 thermally bonded
panels. It is known [19] that the surface roughness alters the way in which the boundary
layer separates from the ball. Changes in the ball’s orientation from one test to another could
easily lead to changes in the way the boundary layer separates from the ball, thus leading to
differences in the lift force. To quantify this effect, we would need to devise an experiment,
either with a wind tunnel or with another approach, that would allow for visualization of the
boundary-layer separation.