The Type S-100 boats were an evolution of the previous Type S-38 boats. Their basic dimensions were the same as the Type S-38, but these vessels were constructed from the beginning with the armoured bridge. Their armament was also increased with an additional gun mount amidships, while additional armour protection was also added around the engine spaces. Other small differences about the Type S-100 boats were an overall simplification of construction, eliminating unnecessary fittings throughout the vessel, giving these boats a streamlined appearance. The hull numbers built for this Type S-100 were S-100, S-136, S-139 through S-150, S-167 through S-228, and S-301 through S-307, for a total of 83 boats in this class. As the construction of this class progressed, improvements were made not only in construction techniques, but in increased engine performance and also in the armament carried. S-170 had the first set of Daimler-Benz MB 518 diesel motors, rated at 3000hp installed for testing, increasing the top speed to 45 kts. S-219 had its fuel capacity increased to extend the radius of action by 50nm. S-226 had a pair of rear-firing torpedo tubes installed, the basis for the design of the Type S-700 class. S-301 through S-307 were to receive the MB 518 motors, but it is believed that the production of these motors was canceled and these boats were built with the then standard MB 511 motors. There is also information pointing to, at the least, the experimental fitting of a 20mm ‘Flakvierling’, or quad mounting on a few boats, but no photographic evidence has been located to support this, only design drawings.
The Type S-700 boats built carried the hull numbers S-701 through S-709, nine boats in all. The design benefited from all the experiments done on S-170, S-219, S-226 and other Type S-100 boats. Like the S-301 through S-307 boats, they were to have the MB 518 motors, but it is possible that these boats were completed with the MB 511 motors. It is also quite possible that they were not built with the armament upgrades designed, but were basically a repeat of the Type S-100 class.
