I saw a glider with the Sinha (sp?) deturbulator tape this last
weekend. The owner was explaining the theory of how that works, and
it seems to revolve around the turbulent stream hitting exactly at the
location of this tape, which would explain why it works only at that
speed. I thought about this question just after talking to him: Why
not coat the whole aft 2/3 of the wing with the deturbulator material,
then you would cover all the possible reattachment points? Of course,
as a scientist, I wonder about the validity of any test where the
proponent says that "You have to take each test individually, not
aggregate them together." Sounds like anecdotal evidence to me.

But, assuming that this would really work, then you could have what
the owner described as a "induced drag only" wing, and it L/D would
depend only on fuselage drag. So, a wing like this on a really
streamlined fuselage (Diana?) might see high L/D speeds.

Just my $0.02,
Ed