You don't need to be calculating Angle on Bow.
Just look at the ship and use the Recognition Manual as a guide.
Or, if you have map updates on or have plotted the target's course, then just look at the map and eyeball it.
I fear that if you worry about calculating it, confusion may result. And it is really not necessary. Just get close and position the boat to get lots of 90° AoB shots.
IMO, only after you are proficient at knowing AoB good enough to sink ships, only then worry about calculating the AoB (and then only if you really want to for some reason) for distant or other 'trick' shots.
__________________
.-. --- ..- --. .... ... . .- ... .- .... . .- -..
|