Tom,
did you approach from behind? I managed to slip nicely in between two columns and only turned to make an attack run when I was right in there,
And I passed within 400 meters of more than one boat without them even bothering with me...
Until the ammunition ship in the middle of the convoy exploded of course :P
Circled in red is my tiny little boat, sneaking up.
And here, From the bridge (where the watch officer is in desperate need for a smoke, this is only our second patrol and our first convoy!)
And the aftermath. In red the ammunition ship that was my primary target, and behind it on the diagonal you can see smoke comming off a 3,500 tonner that snagged my stern shot
The destroyers took a good 3 minutes at LEAST to get to me, given I was slap dash in the middle of the convoy (I fired from an AOB of 150 to stbd off the ammunition ship, range about 550). By that time I was 80 meters down and moving at a hard 90 from the speed and direction i fired from. They never even came close.
Both ships sank- the ammunition ship almost immediately, the merchant maybe 20 minutes later as I snuck away.
As there wasn't anything bigger in that convoy really (1 or 2 around the 5k mark), and I had only chanced across it, I sent a contact off to BdU and continued to my patrol grid.