the expected problem with an airfoil designed for full size aircraft... particularly one with intended extensive laminar flow is
that the flow can remain laminar beyound the onset of the adverse pressure gradient... and will seperate more easily... then
after seperation, will transition to turbulant and reattach... the so called "Laminar Bubble"..... Excessive drag and even a hysteresis can result.....
it is possible, that the vibration of the motor is enuff to cause transition... all it takes is like a .004" thick edge of
tape or a monocote seam to cause transition...