The weight of an airplane has a direct influence on its performance.                                                          The design Philosophy of the SD-1 is to keep weight as low as possible while keeping good performance and handling suitable for low time pilot, at the same time keeping it simple to build. Historically the lightest airplanes have always been made of wood. Every boy has tried to glue together a wooden plane or boat. The SD-1 is really just a bigger model, so the average builder should have no problem finishing the plane.  The development of new materials continues non-stop. We are now seeing items in daily use made of carbon composites, with its incredible strength and light weight. Its strength/weight ratio deserves its use in places with high load concentration like spar caps and similar. Top properties are achieved using technology called pultrusion. This is fully automated process which assures constant quality of production and also mechanical properties. That is the reason why we use it in spars and reinforcement of fuselage in the place of undercarriage mounts. The main spar of wing weights 2 kg (ultimate load 7,5 g) thanks to this material.                  The MTOM/empty weight ratio achieves value 2,1.             The design is maximal simple. The ribs of wing and tails are made of extruded polystyrene. Whole plane is covered with plywood and composites are used on complex shapes.    The engine power range is from 22 to 50 HP what should fulfil requirements of each builder.                       Assembly and disassembly of plane is possible to perform by one person in a short time.                                   The plane fulfils requirements of both FAI UL and LSA regulations and also new German up to 120 kg empty weight category.                                                     The aim of our company is the best possible support for builders of this plane and promotion of “small” aviation for everybody.