SUBSIM Radio Room Forums - I don’t understand

I’ll start by saying that I’m not at all good with numbers. I’m fascinated by their magic but they scare me a little because they won’t do what I want them to do.

I’ve recently been re-reading Michael Gannon’s Operation Drumbeat. To summarise very broadly, both in this book and others (eg Iron Coffins), the details of the various attacks set out do not make sense to me, no matter how many times I read them.

Ok. So, with reference to the very useful printable cards that some kind person put on this site a long time ago, specifically the John P. Cromwell attack rules and the Dick O’Kane attack rules, very often, in the said books, approaches and gyro angles are given that conflict entirely with these and with other information I have read. For example a very shallow AoB as often quoted—20° for example—would seem to only make things more difficult and a torpedo hitting at that sort of angle would glance off the target’s hull.

Similarly where gyro angles are given, the angle is often very large, and I’ve read from more than one source that (as with the attack rules referred to) best results come from a gyro angle close to 0° because the greater the angle, the more likely is the torpedo to deviate from the correct track.

On a rainy Sunday I decided to set up an experiment, the purpose of which was to try to investigate and understand these contradictions. I created a mindlessly simple ‘mission’ with my sub and a target vessel on reciprocal courses. I eliminated as many variables as I could.

I figured—reminder; I’m not good with numbers—if the Dick O’Kane method worked when at 90° to the target course, it should work, with appropriate alterations to the numbers, at other angles. So pointing the scope up 90°, I set the AoB to 90 Stb minus lead angle of 10°. My logic—I’m not good with numbers remember—said that when I am at A, and the target is at B, the AoB is 90° stb. Although there might be a deviation due to the angle (if such is modelled in the game), it wouldn’t be very far off. But it was; very, very far off.

I tried again, this time at 45 ° with AoB at 45° stb minus lead angle, point up aiming bearing, same result. I tried using the ‘scope to achieve the lead angle and I tried using the gyro angle indicator to achieve the lead angle. No matter what angles and permutations I tried the result was always that the torpedo passed a long way ahead of the target. Consistent at least and that lead me to think that I had failed to take something into account, WHAT? What have I failed to take into account?

NB I created a diagram to illustrate this but the Insert Image wants an URL and I can't see a way to simply attach the diagram to this.