The Akaflieg Braunschweig SB-7 Nimbus is a Standard class glider designed and built in

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

in the 1960s. It was one of a series of mixed

glass fibre Glass fiber ( or glass fibre) is a material consisting of numerous extremely fine fibers of glass. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the inventio ...

and wood designs from the students of

Akaflieg Braunschweig Akaflieg is an abbreviation for ''Akademische Fliegergruppe'', groups of aeronautical engineering students from individual German universities of technology and Technische Hochschulen, pre and postwar, who design aircraft, often gliders. Histor ...

Design and development

The Akaflieg Braunschweig or Akademische Fliegergruppe Braunschweig () is one of some fourteen German undergraduate 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 Nimbus was a development of the SB-6 Nixope. The main differences are the shorter span, 15 m rather than 18 m, and the

T-tail A T-tail is an empennage wikt:configuration, configuration in which the tailplane of an aircraft is mounted to the top of the vertical stabilizer, fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs fr ...

of the Standard class Nimbus. Wing construction was simplified by the introduction of a long rectangular centre panel. Like its predecessor, the Nimbus was built from a mixture of wood and

. Its shoulder mounted wings are built around box spars with glass fibre flanges and covered with glass fibre laid over

balsa ''Ochroma pyramidale'', commonly known as balsa, is a large, fast-growing tree native to the Americas. It is the sole member of the genus ''Ochroma'', and is classified in the subfamily Bombacoideae of the mallow family Malvaceae. The tree is fa ...

. They have an Eppler profile, 2° of dihedral and a taper ratio of 0.49. Schempp-Hirth airbrakes are located at 75% chord. The tail unit is constructed in the same way as the wing and all surfaces are straight tapered. The narrow chord,

all-moving tailplane A stabilator is a fully movable aircraft horizontal stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional horizontal stabilizer (whic ...

is mounted on top of the

fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. F ...

. The

fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...

of the Nimbus is a glass fibre

monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...

over balsa. It tapers gently from wing to tail; forward, the cockpit has a long, one piece

canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...

. The Nimbus has a retractable monowheel undercarriage, assisted by a tailskid. The Nimbus first flew in October 1962. It performed very well, but the Eppler wing profile made it a challenge to fly. The recognition of this problem led to the SB-8 but also to a progressive series of modifications to the SB-7. The Eppler wing profile was replaced by one of Wortmann FX-61-163 form, the span increased to , the tail and

geometry revised. It was also given a reshaped, two piece canopy, improved airbrakes and a tail parachute. Another SB-7 was built by Paul Kummer and Oscar Weisendanger in

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

which had yet another new wing of span of , an aspect ratio of 20.85 and a different Eppler profile, 417 rather than the original 306. In addition the wing mounted airbrakes were replaced with a landing

parachute A parachute is a device designed to slow an object's descent through an atmosphere by creating Drag (physics), drag or aerodynamic Lift (force), lift. It is primarily used to safely support people exiting aircraft at height, but also serves va ...

. This version first flew 20 May 1967 and was followed by either one or two more aircraft more prototypes.

Operational history

Despite its newness and difficult handling, Rolf Kuntz flew the Nimbus into second place at the 1962 German National Championships, held at

Freiburg im Breisgau Freiburg im Breisgau or simply Freiburg is the List of cities in Baden-Württemberg by population, fourth-largest city of the German state of Baden-Württemberg after Stuttgart, Mannheim and Karlsruhe. Its built-up area has a population of abou ...

. Because of its retractable undercarriage the 15 m span SB-7 had to compete in the Open, rather than Standard class at the 1963

World Gliding Championships The World Gliding Championships (WGC) is a gliding competitions, gliding competition held roughly every two years by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are always held in the sum ...

, held at Junin in

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

, flown again by Kuntz. He finished 17th in a field of 25. It also competed in the German Nationals held at Roth in 1966, this time in the Standard class and flown by Eckhard Möllendorf. The original Nimbus flew with the Akaflieg for 16 years. It was taken out of service in 1977 but was restored and reflown from 1982 until badly damaged in a landing accident in 1994. It was again restored, making its first flight for over 17 years on 1 November 2011. One Nimbus remains on the German civil aircraft register in 2010.

Specifications (original)

References

External links

Wortmann FX-61-163 airfoilEppler 417 airfoil
{{Akaflieg Braunschweig aircraft 1960s German sailplanes Akaflieg Braunschweig aircraft Aircraft first flown in 1962

Design and development

Operational history

Specifications (original)

See also

References

External links