Welcome to the forum! I feel your pain, as a newbie. Convoys seem to be a waste sometimes. Especially after I just snuck up on one outside of Gibraltar, lots of merchants, get in close and....the biggest ship is a medium merchant.

Five torps, I hit it 2x, hit a coastal freighter, and missed two smaller targets. On the plus side, the sea went from glass to 6 knots just before I attacked, so evasion was a piece of cake.
So I'm tempted to ignore convoys and focus on little guys, but I guess the nice thing about convoys is you never know when you're going to get nice fat, juicy targets and sometimes, when you get a whole bunch of 'em! Plus, I figure it's pretty important to practice on convoys early in the game before the escorts get REALLY good at their game!

Good luck, and screw Bdu!