An item reported that Germany succeeded in improving the submarine weapon and finally managed to built 1.500 ton submarines with a range of more as a month. However plans to armour submarines sufficient against gunfire and depth charges were not executed while this disturbed the stability while coming to the surface. The well known professor Flamm (1) of the Technical High School at Charlottenburg succeeded in theoretically armouring submarines thanks to a new stability system. He designed a 1.443 ton submarine with a 3,5cm thick armour and a surfaced speed of 17,5 knots. Designs for a 4.870 ton submarine with a speed of 25 knots were almost completed.
Note
1. This must be Oswald Flamm (30 July 1861 Dusseldorf-1935), in 1888 graduated as engineer in shipbuilding and ship machinery. Just 31 years old became he professor in shipbuilding at the Technischen Hochschule at Charlottenburg. He was specialized in how screws functioned, stability of ships and building of submarines. The magazine Popular Science dated July 1930 mentioned that he invented invisible torpedoes and that he offered this design to a not specified European government [France regarded the Surcouf-design?] while Germany was not allowed to built submarines since the First World War. The edition dated December 1927 reported that he invented a submarine cruiser of 7.067 tons with a length of 
