On Monday, September 5, 2016 at 10:22:02 AM UTC-4, wrote:
Possibly some of these aircraft have laminar separation bubbles
that are made better by tripping the flow directly to turbulent.

As I think I understand it...

A turbulator is used to transition laminar to turbulent flow to
avoid laminar separation; the turbulent flow causing less drag
than a big bubble. Turbulators can be a relatively thin tape, or
blow holes...

A vortex generator is a lot taller, and is used to pull
higher-speed flow down to the much slower boundary layer,
and create a vortex that inhibits span-wise flow in the
slower boundary layer. That can be used to prevent separation
in some cases; either in laminar or turbulent flow.
It also be used to aid in cooling - there was a great article
recently (KitPlanes ? Sport Aviation?) about a rear-engined
canard that needs tall turbulators to get air into the
aft cooling scoops.

Gary - start with some thin tell-tales and a GoPro to look
at the flow around the top wing surface at the root, aft
of the spar.

Hank - Could Gary be seeing the same issue as the 20's
experience - double-bad-adverse-gradient at fuselage
junction? You install turbulators on the 20 top surface
at the root for this, no?

Interesting stuff....
Best Regards, Dave