Outdated????? The S-Boat was the first submarine to be optimized for underwater performance, beating the Type XXI U-Boat by 24 years! Smaller and with less power than the later fleet boats, it was faster and quicker handling underwater.
However, not having solved the battery problem, when it was time to design a fleet boat, the designers chose to build a surface raider that could submerge when it actually had to. But the S-Boat absolutely disproves the notion that the Germans were just some kind of alien supermen who designed an absolute breakthrough in the Type XXI because of its optimization for submerged speed. Pure poppycock!
So I'll take that 9 knot surface speed with a smile! The S-Boat was almost 30 years out of date and STILL acquitted itself admirably in WWII. Build some new ones with decent ice cream machines and they would have been good for another 20 years.
