The B13 prototype is the first side-by-side high-performance glider with a propeller that is retractable via an electric drive. It has a wingspan of 23m. A combustion engine was intended as auxiliary drive in front of the cockpit, inside of the fuselage nose. The retractable propeller guarantees the entire aerodynamic quality during gliding; until the foldable propeller is extended out of the nose in drive modus. The former concept has been completely reworked and realized as an e-motor. Four linear plain bearings of the type drylin® R FJUM-01 are installed in the propeller slide. They are wear-resistant and maintenance-free, smooth running and have a low weight. The electrical motor requires less room in the available installation space in the fuselage nose, compared with a combustion engine. This allowed enlarging the retracting and extending mechanism. By redrafting the mechanical parts and the propeller, the powertrain weighs only 20kg, which makes 70kg available for the battery system. With it, the drive system is able to equip the B13 with a motor driven scope of 100km, and with a sufficient climb rate.
