Wagner built the airplane in secret, using whatever materials he could acquire. Wagner's son Udo, who was seventeen at the time, was a motorbike enthusiast, playing for a Dresden
Motoball club, and was able to secure the purchase of two heavily used
MZ-ES-250/2 motorbikes for 4,500
Ostmarks. He then overhauled them, dismantled and removed the gearboxes in order to allow the crankshafts to turn the propellers, and reversed the polarity of one of the engines. The engine mufflers were rotated 90° due to the crankshaft being repositioned lengthways. Several steps were taken to reduce the amount of noise produced by the aircraft. The propellers, designed according to plans from the 1930s, already set to rotate at around 800 kmh, were prevented from going faster than the speed of sound, and the air inlets on the carburetors were also rotated 90°, and hidden in the chassis
nacelles with the mufflers. The front wheels of the motorbikes, along with their brakes and suspension, were positioned here too. Air channels were created for cooling the cylinders. Before they attached the motorbike engines, Udo and Jörg mounted one on the car trailer and used a
spring balance between the car and the trailer to determine whether the thrust would be enough to power the aircraft. Although the necessary materials (
plywood,
balsa wood,
aluminium,
plexiglass and
polyester were in short supply in East Germany, the family was able to procure them from various
hobby shops, which they visited in a wide area around Dresden to prevent drawing attention to themselves. Wagner's mother-in-law, who lived in the West, was brought in on the plan and smuggled in glass, silk, bearings, and saw blades for cutting the aluminium sheets. The instruments needed for flight and navigation (
altimeter,
airspeed indicator and
compass) were either built by Wagner, smuggled from the West, or purchased on the
black market. Wagner tested all the various elements of the aircraft in order to ensure it would successfully fly, including stress-testing the wing-fuselage connection with the aid of jacks and springs, showing that it could carry at least 2.4 times the intended weight. ==Discovery==