Right on Cobalt!
Fantastic pictorial there. Surface night attacks need a bit (well quite a bit) of planning, but can and do work. The best part about them is if you get the first one off and escape you can repeat it until the sun comes up. The only downfall is doing them with a VII is that you soon run out of torps. But at least you have a lot to show for it.
A thing I'd like to add is to come in decks awashed. I think this cuts down quite a bit on being visually detected. On a VII , 7 meter depth should do nicely.
Also before attacking watch the behavior of the flank escort. Many times they like to turn 90 degrees away from the convoy and shoot out 1000 to 2000 meters. Sometimes they also turn towards the aft end of the convoy for a bit before returning. This is a great time to make your dash toward some nice juicy merchants!
Once again thanks for the tutorial. I hope gets more kaeluns to give it a shot. By far the best part of SH3 is getting in close to a convoy at night on the surface sinkin 2 or 3 ships and getting away only seeing dim spot lights far away!