The aim of the project is to develop an unmanned aerial vehicle platform for safety critical research purpose and make the entire manufacturing, design and testing publicly available as an open source platform. The aircraft was designed by MTA SZTAKI with the aim to serve as a test platform for UAV on-board avionics system development. The preliminary mathematical model is publicly available and is under further refinement. The main goal was to create an easily reproducible aircraft, using accessible parts and simple technologies, which only require ordinary tools. This feature and the available mathematical model combined, make this aircraft a good platform for control research purposes. Since the integration of UAVs to common airspace requires safe aircraft, considerable effort is put in developing safety critical UAVs. The twin boom configuration of the airframe offers duplicated control surfaces, even the elevator is split. This, in addition to the two electric motors enables this plane to serve as a test platform for reconfiguring control developments. The fuselage is entirely reserved for the payload; it can carry up to 1-4 kgs of avionics and test equipment. It has a modular construction: different set-ups can be installed to the frontal section in a few minutes, and the fuselage itself is also easily changeable. The fact that easy reproduction was given priority over weight reduction significantly constrained the possible shapes and the quality of the parts used. As a result of our efforts to reach high standards for the aircraft, good general condition and functionality can be maintained, even after numerous disassembles. The foam and plywood parts made the easy modification possible, and the smooth and shiny surfaces give an aesthetic look to the aircraft. The vast majority of the components are either laser cut plywood or hot-wire cut foam. Such technologies provide the cheap and fast manufacturing of the components. In case of the few parts where the strength of plywood is not sufficient, PCB core material is preferred, since it is a stronger material, and PCB milling is an accessible technology. Additional exceptions are the coverings of the nacelles and the fuselage, which are thermoformed in vacuum. The thermoforming process and the construction of an inexpensive mold is described in this manual. The use of precut parts enables a fast assembly: a new aircraft can be built in about 180 man-hours. For three people, the assembly spans through 8 days, taking the curing times into account.