Cran,
You are quite correct. Thanks for setting me straight.
I had never considered laminar flow with a rough surface to be possible, but indeed, in Prouty's book he states "a rotor blade, even one with leading edge erosion, can maintain laminar flow more easily than a wing, possibly because built-in surface imperfections are usually less and also because pitting is less detrimental than protrusion".
That's good to know.
One does'nt learn while shooting their mouth off, but sometimes it gets a response that they will remember.
Thanks Cran.
slowrotor
(now I have to figure out what a supercritical airfoil is)