Lot's of us have had trouble learning to hit ships. Especially me

! But once you get it down-you've got it! So don't give up!!!
I'll see if I can help out a bit. Make sure you have the speed figured out. I do this the hard way and won't try to detail it here but I usually take at least 15 minutes to figure out speed. Make sure your speed estimate is within bounds of the target types capabilities (in the Recognition Manual).
Angle on the Bow: Pretend you're on the target ship looking at your sub. The angle you are looking from the Target is the setting to use.
Range: Make sure you are using the RFB ranges for your stadimeter. In the Recognition Manual, they are marked in red on each ship. Frequently, you measure the stack height--NOT the mast height as it was originally set (and typically mentioned).
After you set each value, you MUST Enter it by clicking the arrow on your TDC (11 0'clock on the upper right dial). When all values are entered (and clicked in) I typically click the arrow again just before firing. And I can safely say that I hit almost every target I shoot at now. If only the torpedos would explode

.
Hope this helps and that I've made sense. Regardless--hang in there!!! We'll help you out!
Cheers!
Peto