Hi, I was looking at the NASA website's FoilSim application (google it) and for spinning objects, there is a maximum rpm. I was wondering why there were maximum/restricted rpms, so I emailed a NASA guy with the question. He said that the FoilSim App was for middle school students and that higher rpms would create secondary boundary layers, or something like that, too complicated for middle schoolers. He also said that the rpm-lift force relationship remains linear (higher rpm-higher lift force) at higher rpms than allowed in the FoilSim. So then I read about the 'reverse Magnus effect', and now I need a bit of clarification. How would having a rough surface completely negate the reverse magnus effect (according to http://126.96.36.199/search?q=cache...k&cd=1&gl=us ) , and is the NASA guy mistaken when he told me the rpm-lift force relationship remains linear at increasing rpms?