[Tontoman]

Some things I've done, all depends on weather, day/night etc and year

- Get ahead and dive. Try and approach lead destoryer close enough not to get picked up by the side patrol, but not too close so he picks you up, going to convoy at 45 deg angle between the lead and side destroyer. Remember his side spotting is mainly passive (so run silent), just don't get in front (why I wait if I can until he stops doing a search pattern). Soon as you get past, it's all yours. Lots of hydrophone use.

Pros - lots of easy and safe kills once you're in. (my usual method)
Cons - if you blow it, you're shallow and have to evade quick.

- Take out the defending destoryer on the side. Evade, surface, get ahead and attack convoy again but now they are a ship short.

Pros - safe
Cons - two attacks, uses 1-2 torps for destroyer (this is where battery torps come in use).

- Go deep and let convoy pass overtop (has to be slowish convoy). As the merchants get close go high speed (so they don't pass overtop) and go periscope. Destroyers detect you but can't get to you without ramming their own ships
Once you are at periscope depth, blow things up and use ships to get away from destroyers (just don't get rammed). This is where real life is easier than the game. Read a number of accounts where subs where on the surfance between merchant ships. Destoyers didn't fire or chase, in the game they'll still do both using the uber ship brakes built into the game.

Pros - Easy to try, fun and hectic as hell
Cons - Risky, ships are going to be moving all over the place so hard to get clean shots.

Cheers.
T.