On Wed, 09 Jul 2014 23:07:19 +0000, Martin Gregorie wrote:

[zig-zag turbulators are] fitted to my Libelle and evidently makes a
difference: the BGA has separate handicaps for an H.201 and an H.201
with turbulators: the latter is slightly increased.

I should have said that this is full span turbulation on the lower
surface and is placed just ahead of the undercambered part of the lower
surface.

It delays flow separation on the undercambered part of the undersurface
at low AOA: this reduces drag at higher airspeeds.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |