[ttriarsi5689]

Figure out the heading of the convoy, then navigate a few km ahead of them, where they are going to be, and about 1000-2000 meters out at an adjacent angle on the convoy (distance depending on escorts), then sit and wait, with decks awash and engines off for them to come to you. Once your torpedo's are out, don't wait until they hit. Then just creep away from the convoy in the opposite direction than they are going, so if the escorts do acquire you then going the opposite direction will draw them away from the convoy fastest, so hopefully they will break the attack so they can stay with the convoy. Personally I don't mess with a convoy with more than a couple escorts.