Larry Dighera wrote:

Given the "clean" design of the glider, the increase in parasitic
drag at higher speeds is probably insignificant compared to the "skin
friction drag" reduction.

But given that the original poster was most probably talking of
airplanes with noisemakers, I suspect that for him, best glide gets
dramatically worse at higher speeds. As I always say: Airplanes don't
*need* airbrakes because the whole plane *is* just one huge airbrake.

Stefan