08/31/2010. Remarks by Johan Visschedijk: "Friends since their youth, Harald Undén, Sven-Olof Ridder and Lars Bergström formed RADAB (Research And Development AB) in 1964, during the time Ridder and Bergström were engineering students at the Royal Institute of Technology at Stockholm, Sweden. All three men had a strong interest in building and flying model airplanes, however, the company started with repairing sailing boats.
It was not until the late 1970s plans for aircraft design formalized and to meet the requirements of JAR 22 (Aerobatic category), Undén and Ridder designed a small single-seat self-launching glider for amateur construction in 1981. Designated Windex 1100, prototype construction started in January 1982, and registered SE-XSD it made its first unpowered flight on March 15, 1985, a large piece of lead substituting the engine. Test flying with a 22 hp Limbach engine started in the summer of 1985.
The Windex 1100 had hot-wire shaped wings of 36 ft 1.1 in (11.00 m) span, but the pictured production prototype, built in 1989 and designated Windex 1200, had Nomex honeycomb molded wings with a span of 39 ft 4.4 in (12.00 m), though the wing area remained unchanged. The tailplane, originally mounted halfway up the fin, was been raised to a T-configuration to simplify rudder geometry and improve elevator efficiency.
Production kit aircraft, designated Windex 1200 C,had a span of 39 ft 8.3 in (12.10 m) and were to be powered by either a 25 hp RADAB powerplant, comprising three chain-saw cylinders in line, or a 20 hp König SC-430 three-cylinder engine. Reportedly some forty kits were produced from 1992 on (Windex production was taken over by the newly formed WINDEXAIR AB in 1999), that were assembled by amateurs in Sweden, Costa Rica, France, and the USA, the first flew in 1996."