Don't confuse the Cl/Cd diagram of an airfoil with the CL/CD diagram of an airplane.
The airfoil is only a 2D representation of a section of the wing. For the real airplane, you have to account for the fact that the air flow is 3D (finite wing length, induced drag) and other parts of the airplane that contribute more to drag than to lift, e.g. the fuselage, gear, tail planes etc.
Take these into account and you will end up with a higher CD, and hence a lower speed for optimum glide.
The stall speed is not affected by the extra drag, since the maximum CL remains largely unchanged.
ATCast
Last edited by ATCast; 4th Feb 2010 at 12:10.