The Akaflieg Darmstadt D-30 Cirrus was an aerodynamically advanced single seat sailplane with a very high aspect ratio wing and a pod and boom fuselage.
Instead, a single, wide, tapering duralumin spar was built up out of corrugated sheets, with upper and lower skins that formed about one third of each wing surface at the root and more at the tip.
Ahead and aft of the spar the wing profile was shaped with wooden ribs and plywood skinned.
Since higher camber airfoils stall at greater angles of attack measured from the zero-lift line, the combination of higher camber and washout means that the stall develops inboard and that the ailerons, on the unstalled outer wing, retain lateral control and can prevent entry into a spin.
The other unusual and possibly unique wing feature was that the dihedral of the outer panels (there was none inboard) could be varied in flight though large angles (+8.5/-4.4).
[1][3] The Cirrus, flown by Bernard Flinsch, set a new world record out and return distance in 1938, flying 306 km (190 mi) from Bremen to Lübeck and back.