[UKönig]

Force equals mass times acceleration. Just make sure the ramming target weighs less than your U-boat, or is so badly damaged that a good shove would be enough to break it in half. Otherwise, I try to avoid deliberately colliding with ships. One of the sounds I really hate is that grinding of metal on metal when I introduce the conning tower to the keel of my victims.
However, I did take out 2 elco torpedo boats with one T1 of my own. They were sitting in harbour, one crossing the T with the other, so I aimed at the one in back and the explosion blew them both out of the water in opposite directions. Sweet. I always wondered if that would work...