Akaflieg Braunschweig SB-7 Nimbus
The SB-7 Nimbus is a development of the Akaflieg Braunschweig SB-6 Nixope, an ultra high aspect ratio high-performance single-seater with an 18m (59ft 0in) span wing, an aspect ratio of 25 and a best glide ratio of 42:1.
The SB-7 Nimbus, which first flew in October 1962, featured a 15m (49ft 2.5in) span wing for StandardClass requirements with a lower aspect ratio, and a T-tail instead of the SB-6's lower-mounted tailplane.
The SB-7's shoulder wing has a box spar with glassfibre flanges and is covered with diagonally-laid glassfibre skin stabilised with balsa; the ailerons are of wooden construction and there are two Schempp-Hirth air brakes on each side at the 75% chord line. The fuselage, again like the SB-6's, is a glassfibre monocoque stabilised with balsa. The tail unit is of similar construction to the wing, with the one-piece all-moving tailplane on top of the fin.
Landing gear is a retractable monowheel with friction brake and there is also a tailskid.
In Switzerland an SB-7 was modified by Paul Kummer and Oskar Wiesendanger of Zurich to have a completely new wing of increased span (54ft 2.5 in) and aspect ratio (20.85) and with an Eppler 417 aerofoil section; trailing edge air brakes replaced the Schempp-Hirth ones of the standard SB-7 and a tailbraking parachute was fitted. The first of two prototypes of this modified SB-7 made its maiden flight on 20 May 1967, and two more prototypes were built.
Span: 17m / 49 ft 2.5 in
Length overall: 22 ft 11.5 in
Height over cockpit: 2 ft 8 in
Wing area: 12.66 sq.m / 127.6 sq.ft
Aspect ratio: 19 / 22.83
Airfoil: FX 61-163
Empty equipped weight: 283kg / 562 lb
Max take-off weight: 390 kg / 794 1b
Wing Load: 30.8 kg/sq.m
Max speed (smooth air): 158 mph
Min sinking speed: 0.60 m/s / 2.20 ft/sec at 56 mph
Best glide ratio: 37.5:1 at 85 kph / 56 mph
No. of Seats: 1
No. Built: 1