Separation bubbles?
OT: BTW, my experimental glider was a full-sized HG, and I tested it both
clipped-in and unclipped. The second method was preferable, as the first
allowed the glider to drag me all over the beach at Kitty Hawk. I should note
that when I designed this machine, I had very little understanding of the fine
points of non-rigid delta-wing aerodynamics. There's a photo of it on my
website. Its the "Stormy Petrel 3" photo. The "Stormy Petrel 2A" was a
modified "Batso" glider and flew fairly well.
Harry
http://hometown.aol.com/wright1902/page3.html