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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.

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  • $\begingroup$ Do you confirm the design shown in the picture is for longitudinal stability (like the reflex camber)? $\endgroup$
    – mins
    Nov 30, 2017 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. $\endgroup$
    – jkztd
    Nov 30, 2017 at 20:05
  • $\begingroup$ Somehow related Airbus patent. It also involves vertical surfaces drag to compensate a negative pitch. $\endgroup$
    – mins
    Dec 1, 2017 at 14:39
  • $\begingroup$ I and a few hobbyists online have experimented with the opposite of this - lowering the fuselage and using the pendulum action (basically gravity instead of drag) to stabilize non-reflexed flying wings. In the real world you will commonly see human piloted full scale "aricrafts" of this configuration in the form of paramotors using non-reflexed parafoils/parachutes $\endgroup$
    – slebetman
    Sep 13, 2019 at 7:03
  • $\begingroup$ Here's the RCGroups thread on the pendulum stabilized non-reflexed flying wings: rcgroups.com/forums/… $\endgroup$
    – slebetman
    Sep 13, 2019 at 7:07

2 Answers 2

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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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This design rings the bell as an abstract Mig-15, essentially providing pitch stability and yaw stability with a "tail". A conventional layout in disguise.

High T tails, common in sailplanes, use horizontal stabilizer drag to lever the wing to its proper AOA, saving a little bit of trim drag.

Conventional tails also take the less efficient (greater drag area, shorter torque arm) "reflexed camber" from the back of the wing and put it on the more pitch control efficient horizontal tail. (If you have a fuselage full of cargo or passengers, why not put a tail back there?). Maintaining AOA with minimal drag producing oscillations is critical to long distance fuel efficiency.

Another variation to this design would be to sweep the wings for yaw stability. However with this one there will be less yaw-roll coupling. The X-15 had a "wedge tail" for hypersonic yaw stability, a good straight V stab and rudder would suffice for this concept.

One can see the lower aspect "Hershey Bar" has enough pitch stability to make this model work, especially with a smaller weight to surface area ratio. As you get more massive, more pitch authority is required.

You will note flying wings have yet to put conventional sailplanes out of business.

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  • $\begingroup$ This does not seem to address of the OPs question: "Who thought about this configuration and does anybody have documentation about this?" and only briefly touches on "What kind of max L/D ratio and finesse could this Clark Y drag stabilized config could reach compared to reflex airfoil [...]" (you say a reflex airfoil is less efficient, but do not elaborate on this, which is the crux of the question). $\endgroup$
    – AEhere supports Monica
    Sep 13, 2019 at 8:12

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