What provides lift is the wing, but it is unstable without one stabilizer.

Flying wings airfoils, or reflex airfoils, carry their stabilizer inside them, through a reversed camber of the trailing edge section. Those airfoils provide less lift and more drag than "standard unstable cambered" airfoils.

Long time ago I (don't know where anymore) saw images of one particular wing longitudinal stabilization method, which could allow one "standard unstable high lift" or let's say Clark Y airfoil, to fly stabilized by the drag produced by one surface placed quite far above the trailing edge.

This looked like this, and models of it fly pretty well :

enter image description here

Who thought about this configuration and does anybody have documentation about this?

What interests me in this is : What kind of max L/D ratio and finesse could this Clark Y (or RG 14 or else) drag stabilized config could reach, compared to reflex airfoil (Eppler 187 or else) of same wingspan, same wing loading, same geometry glider.

Note the impossible sustained reverse flight.

  • $\begingroup$ Do you confirm the design shown in the picture is for longitudinal stability (like the reflex camber)? $\endgroup$ – mins Nov 30 '17 at 19:55
  • $\begingroup$ @mins yes, with appropriate CG, lever arm and surface proportion, it is auto stable on pitch axis, even if the red drag surface is not controllable: If accelerating In a dive, drag increase on red part pitches up the airplane, if slowing down during a climb, drag reduction on red part pitches down the whole thing, until equilibrium. $\endgroup$ – qq jkztd Nov 30 '17 at 20:05
  • $\begingroup$ Somehow related Airbus patent. It also involves vertical surfaces drag to compensate a negative pitch. $\endgroup$ – mins Dec 1 '17 at 14:39

If you’re going attach a boom and surface, why are you comparing to a reflexed airfoil? Attach the boom and surface conventionally and you get far better LD than either. The effective trim drag is lower. And you can get it thru the door of the hangar. Planks are cool, but applying the restoring force without much lever is the basic problem. The required force and resulting drag is much higher. The new config exposes the whole boom to flow and the vane is 100% drag. A conventional surface generates force with the L/D of the tail surface, only 20% drag if the LD of the tail is 5. Conventional boom or even a swept tailless is far superior to this config or reflexed plank. I don’t think anyone will spend time calculating the diff between two poor config. Sorry.


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