Question: When was the aircraft manufacturer at which Klapmeier brothers was a co-founder founded? 
Sentence (from "Weller Flugzeugbau"): The company has done contract specialized welding for automotive companies, including DaimlerChrysler, Porsche and BMW as well as work for aircraft manufacturers, including Scheibe Flugzeugbau and Sauer aircraft engines, and aviation museums, such as the Musée de l'Air, Deutsches Museum and the Technikmuseum Speyer.
Relevant evidence: No