It was thought that enough had been learned from the Nietoperz to enable a tailless sailplane to be built that would have flight characteristics and handling not much more difficult than an orthodox type. The design of the SZD-13X Wampir 1 began in 1955, with wind tunnel model tests to confirm the major features, but this project was shelved for three years because of other work. When revived the SZD-20X Wampir 2 resulted. It was intended to have a wing similar in general dimensions to that of the Mucha, to enable performance comparisons to be made on a fair basis. (...) Adam Zientek carried out test flights in September 1959. Taking off from anything but a very smooth surface was difficult. (...) On aerotow, entry to the slipstream caused loss of control. The airbrakes caused strong pitching tendencies when landing and needed care. The first stalling test produced a spin. (...) Finally, during a test at moderately fast gliding speed, serious flutter developed and a bale out became necessary. The Wampir project was abandoned.