Banktoturn,
It was not my intent to make a correlation or distinction between the two... it's obvious to all that as one approaches zero thickness the section must become flat.

FWIW, A thin section even if slightly rounded will typically force transition very near the leading edge which is what makes these "thin" sections Re independent. If the Re gets too low you'll want to force transition which is easy too.

When I say transition I do mean laminar to turbulent. Thin sections do this naturally without any help. Clmax simply doesn't matter for aerobatics...you can get the force you need from area or dynamic pressure while we're talking dimensionally.

Call them fins, wings, foam, wood, flapper-dappers...call it whatever you like...if it supports a pressure distribution that's all any of us are interested in.

If you study handling qualities you'll find that pilots opinion of an airplane are often driven by how linear the airplane's response is to a control input. From and Aero/S&C point of view we've found that when the aerodynamic forces and moments changes linearly with changes in angle of attack, sideslip and control surface deflection the pilot's opinion is typically high especially when tasked with precision flying (not necessarily 3D). This also goes for these forces changing with Re.

I would agree that a flat plate's lift curve is probably just as linear as a thin section of equal thickness. Also the CLmax of both sections will be similar because both sections are almost identical. The flat plate is certainly easier to produce and more readily available which makes it the section of choice if you subscribe to the Ockham's razor approach to aerodynamics and engineering. We're piddling again...


George Hicks

Since we're stating the obvious... the strength actually comes from the combined material properties and the moment of inertia (which can be a function of section shape) of the structure not just thickness as you mention.