I always use straight flank shots (0 angle shots).
I use a 'torpedo bearing table' with the target speed and according bearing, so as long as you have the target's course and speed correct, it's a sure hit.
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I hit my targets about 95% with this. I'm still surprised I seem to be the only one doing it this way. It's effective and the most simple attack to perform.
If there are multiple ships, I vary the speed of the torps just to make them go off at about the same time, so the next one will not have too much time to excellerate or drop speed.
This is about how they did it in world war one or so I heard
The 'torp bearing table' can be downloaded here as part of a collection of stuff:
http://www.subsim.com/radioroom/down...o=file&id=1487