You have to remember what the angle on the bow is. It has nothing to do with your course, but everything to do with the target's course. That might make the name "angle on the bow" a bit misleading. I find it an unhelpful term. But we didn't make it up and we're stuck with it.
The angle on the bow is nothing more fancy than your bearing from the target! But instead of using zero to 360º, the angle on the bow is measured from zero at the bow of the target to 180 at the stern. Because for any angle on the bow less than 180, there are TWO angles of the same measure, we differentiate between identical 88º angles by 88º starboard and 88º port. You pick starboard or port based on which side of the target you see. If you were German, none of this explanation would be necessary because on a U-Boat all bearings are measured in this way.
So what's the best way to measure angle on the bow? If you want to be strictly historically accurate, the majority of the AoB measurements in the war were done by visual evaluation. Gutted's Solution Solver has a great practice tool for that so that you can learn to see the aspect of the target and estimate the AoB accurately enough to whack 'em between the eyes.
However, I'm a plotting geek and I like to collect all my info from the plot. I take a sighting of range and bearing, with radar if possible and plot the position of the target. Then I wait three minutes and do it again. By connecting the two positions with a line and extending it in the direction of target movement we establish the course of our target. But we can also measure the number of hundred yards between the point and that is the speed in knots. 700 yards equals 7 knots. Put that into the TDC.
The angle on the bow is your bearing from the target. So use the protractor. Click on the target track ahead of the target, again on the middle of the target and a third time on the middle of your submarine. You'll see the angle measurement at the apex of the angle. That's your AoB. Is it starboard or port? If you are looking at the target's starboard side it is starboard. Easy enough? Enter that puppy. Note the course on the outside
Lastly, you need an accurate position with a final sighting of range and bearing. It is vitally important that the range and bearing be input last, after speed and target course/AoB are in the TDC. Entering information out of order will result in misses astern. Send that to the TDC and you're ready to shoot.
You can check your setting by going to the attack map. You will see the position of the target, and also see the x where the torpedo will hit. There is a vector pointing forward from the x. Is the x superimposed on the target? Is the vector pointing in the direction of the target's course? Also displayed is the torpedo run time. Watching the attack screen, does the x remain on the target for the length of that run time? If you have a 3:20 run time and the x stays on top of the target for that length of time, you have a winner for a setup. Take one last position sighting and shoot with confidence!
