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Akaflieg Braunschweig SB-11 Antares
The SB-11 Antares is a single-seat high performance research sailplane categorised in the FAI Unlimited Standard Class and intended to test a new variable geometry flap system and to evaluate the use of carbon-fibre reinforced epoxy resin as a constructional material for all parts of a glider.
Design work on the SB-11 started in the spring of 1974 and construction of the sole prototype began in April 1976; this made its first flight in May 1978.
The constant-thickness Fowler flap system is designed to achieve a high average cross country speed without the operational and technical difficulties of a telescopic wing, as tried on the Akaflieg Stuttgart FS-29, a high aspect ratio giving a very long span wing or a slotless Fowler flap-type wing. To retain conventional sailplane handling characteristics a constant thickness Fowler flap was devised that avoided friction between wing and flap and the need for a flexible lip at the lower surface of the wing. A special Wortmann wing section was evolved for the SB-11 and this was flight-tested mounted on the nose of a DFS Kranich 3 sailplane; the results were sufficiently encouraging to believe that the SB-11, with flaps extended, could outclimb any other Standard Class sailplane and, with flaps in, it would perform as well as a conventional Standard Class type. The cantilever shoulder wing is of 15m (49ft 2.5 in) span and has an aspect ratio of 21.3 with flaps in or 17 with flaps out; in the former condition the best glide ratio is 41:1. There is a single carbonfibre spar with roving spar flanges; the outer shell is a carbon-fibre/plastics foam sandwich. Each wing trailing edge is made up entirely of a 25% chord slotless Fowler flap inboard and outboard a 'flaperon' of 22% chord when in and 17% when extended; both flaps and 'flaperons' are of carbonfibre/plastic foam sandwich construction. They are supplemented by Schempp-Hirth air brakes on the upper surfaces of carbon-fibre/balsa wood sandwich construction, and wing tanks provide for up to 100kg (220lb) of jettisonable water ballast. The fuselage is a carbon-fibre monocoque and the cantilever T-tail, which as an all-moving tailplane with spring trim, is a carbon-fibre/plastic foam sandwich except for the rudder, which is a glassfibre/plastic foam sandwich. There is a retractable unsprung monowheel with an internal drum brake, and a rubber-spring tailskid.
The carbon-fibre monocoque fuselage front was cast in Schleicher AS-W 20 moulds. The T-tailed rear fuselage was made on Schempp-Hirth Janus moulds.



The SB-11 made its international debut at the 1978 World Championships at Chateauroux, France, when it was flown into first place in the 15m class by Helmut Reichmann, and in November that year it was named Antares.
Span: 49 ft 2.5 in / 15m
Length: 7.4 m / 24 ft 3.25 in
Height: 1.47 m / 4 ft 6.25 in
Wing area (flaps in): 10.56 sq.m / 113.7 sq.ft
Wing area (flaps out): 142.1 sq.ft
Aspect ratio (flaps in): 21.3
Aspect ratio (flaps out): 17.0
Airfoil: Wortmann FX-62K-144/21-VG-1.25
Empty weight: 573 lb / 265 kg
Max weight: 1,036 lb / 470 kg
Water ballast: 100 kg / 220 lb
Max wing loading: 44.5 kg/sq.m / 9.11 lb/sq ft
Max speed (flaps in; smooth air): 155 mph / 140 kt / 260 km/h
Max aero-tow speed (flaps in): 112 mph / 97 kt / 180 km/h
Stalling speed: 31.5 kt / 58 km/h
Min sinking speed (flaps in): 0.62 m/sec / 2.03 ft/sec at 50 mph / 43 kt / 80 km/h
Best glide ratio (flaps in): 41:1 at 64.5 mph / 56 kt / 104 km/h
Best glide ratio (flaps out): 36.1 at 53 mph
No. of Seats: 1
No. Built: 1



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