So far, my usual method for attacking a convoy is to use the ruler to draw a baseline of their projected course and the protractor tool to mark a 90 deg. line to plot my interception point.
I set myself up a few km ahead, go to 40m depth and sit quiet while I mark my targets as they approach, trying to ID ships by their sound. I then nudge into the lanes and drift as the escorts pass by overhead.
Once the first few rows of merchies go past, I rise to periscope depth and start launching my torps, using my stern tube for the smaller ships that usually occupy the outer column behind me. I turn as needed to line up my targets, aiming for the boilers, one eel per target.
The idea there is to cripple as many ships as possible, forcing the bulk of the convoy to leave them behind. I go as deep as I can and try to evade and wait out the escorts until they have to leave to protect the convoy. Once the coast is more or less clear, I rise back to 14m and finish off the damaged ships with my reloads or deck gun, if seas permit.
Of course, that's not the only way I go after convoys but it's the method I use most often.
With my 13th patrol set to begin sometime in March 1941, I'm sure that a lot of tricks and tactics I've learned will need to be changed or replaced very soon.
