Akaflieg Braunschweig SB-11

SB-11
Role	Experimental single seat sailplane
National origin	Germany
Manufacturer	Akaflieg Braunschweig
First flight	1978
Number built	1

The Akaflieg Braunschweig SB-11 is an experimental, single seat, variable geometry sailplane designed by aeronautical students in Germany. It won the 15 m span class at the World Gliding Championships of 1978 but its advances over the best, more conventional, opposition were not sufficient to lead to widespread imitation.

The Akaflieg Braunschweig or Akademische Fliegergruppe Braunschweig (English: The Brunswick Academic Flying Group) is one of some fourteen German student flying groups attached to and supported by their home Technical University. Several have designed and built aircraft, often technically advanced and leading the development of gliders in particular. The announcement, in 1975, of a new, unrestricted 15 m glider class led the Brunswick group to the design of the SB-11, a variable geometry aircraft.

A long-standing challenge for the designers of competition sailplanes were the conflicting requirements posed by the need to gain in height in sometimes weak and narrow thermals, calling for high lift and low stalling speeds for small radius turns, and the need for rapid penetration of the cool, sinking air between thermals. In thermals, wings should ideally be of high camber and be lightly loaded; between them, low camber wings with high wing loading would fly faster. Large area, camber changing flaps were one solution but vortexes generated at their extremities added significantly to the drag, decreasing climb rates. Akaflieg Brunswick decided to follow the example of the disappointing British Sigma by providing the SB-11 with Wortmann flaps along the whole of the trailing edge of the wing, including the ailerons. This avoided the flap associated vortexes, though any increase in wing area, however implemented, will lower the aspect ratio and raise the induced drag caused by wingtip vortexes.

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