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Herbert Gropp designed this motor glider in 1930 during his studies at the Chemnitz State Academy of Technology in order to be able to provide the members of his Aeronautical Working Group (FAG) with an aircraft for practical training. He managed the construction on his parents' property in Siebenhöfen near Geyer. He opted for a motorcycle engine from J.A.P., which produced 9 hp at 1200 rpm and initially drove a duralumin pneumatic screw that could be adjusted on the ground, but Gropp soon decided to replace it with a wooden propeller. The design consisted mainly of the hull boat with the engine in the rear area and the tail unit connected to the hull by struts. A sprung runner served as the chassis. The glider was completed in 1930 and Gropp carried out the first flight of 200 m in length at a height of about 1 m at Chemnitz Airport by bungee cord launch. However, since Gropp was only in possession of the paragliding licence A and his aircraft did not have a licence, he was prohibited from making further attempts by the aerodrome authority. He therefore transferred it to the FAG Chemnitz, which christened it the Zaunkönig on 7 December 1930 in a ceremony in the presence of the Academy's professorial staff.

Gropp successfully completed his studies in March 1931 and subsequently took up a position in the testing department of the DKW engine works in Zschopau, where he succeeded in arousing the interest in the wren in the chief engineer of the racing department, August Prüssing, so that he provided him with a self-designed boxer engine as a new drive, which weighed only 17 kg with the same power as the J.A.P. engine. The FAG students made a new wooden propeller for this purpose and made some changes to the glider; so an additional strut was pulled in from the fuselage stern to the side fin as reinforcement. Modified in this way, the wren was flown publicly on September 27, 1931 by Hans-Joachim von Hippel, a former fighter pilot of the First World War, in front of an audience at Chemnitz airfield. The wren proved to be completely self-launching capable and stable in flight.

According to von Hippel's experience on these flights, the aircraft received modified ailerons made of tubular steel and plywood planking for the leading edge of the wing the following year. However, flights were no longer carried out and the wren sheltered in the rooms of the Chemical Institute showed serious bearing damage after some time due to penetrating moisture, which attacked the glue joints. Finally, in May 1933, a wing was dismantled in order to be used as illustrative material for the Academy. At the same time, this meant the end of the wren, which, apart from Gropp's short maiden flight in 1930, had only completed a total of ten flights with von Hippel. However, it later served Hans Wünscher, who also worked in the FAG Chemnitz, as an inspiration for the design of the C 10 motor glider.


The hull consisted of a tubular steel truss mixed with wood, which was partly covered with fabric and partly covered with wood. The cabin was covered by a moulded canopy, which aerodynamically adapts to the hull contourse, but offered a very limited view ahead. The engine was located behind the pilot in the middle of the rear wing edge, the corresponding fallen fuel tank was integrated into the tensioning tower above.

The wing was designed in two parts and consisted of a wooden frame with a main and an auxiliary spar. The leading edge of the wing was initially covered with cardboard, which was later replaced by plywood. The tail was attached to the fuselage and to the rear wing spar by two struts each. Due to the lack of stiffness of the side fin, it was later reinforced with an additional strut that ran towards the lower fuselage. The landing gear consisted only of a runner with six struts attached to the underside of the fuselage.