ASK21 --- OR --

On Nov 8, 3:15*pm, John Galloway wrote:
Quite the reverse - Dick Johnson tended to find that turbulated gliders
performed better without the tape. *He also usually found lower
performance figures than the manufacturer's (and Idaflieg) polars.

John Galloway

John -

Actually, it depends. On earlier gliders he started finding benefits
to the turbulator tape - which is why he developed the practice of
sticking it on gliders he tested.... That's because earlier airfoils
tended to have laminar separation bubbles, which could be eliminated
by forcing the airflow to go turbulent (which, while higher-drag than
laminar flow, is usually less-draggy than a bubble).

It went on this way until the airfoils developed for some later
gliders started to reverse the trend. I attribute that to the
advancement of high-end wind-tunnels, CFD, and other computer-modeling
techniques that allowed much better prediction and testing of airfoils
for laminar bubbles and other boundary-layer effects.

However, many of the gliders that are still popular today (and flown
in large numbers) use airfoils that can benefit from select
turbulation.

--Noel