I used to have a nomograph on my Nav Map, but I am using nisgeis "brilliant" torpedo angle calculator mod, and it canceled and disabled my poor nomograph.
Just kidding!

I couldn't resist....
re your post:
Excellent idea!

Very good post and a great tool I never thought to apply in this situation. The three minute rule re plotting on the Nav Map is not workable in my opinion. Too much plotting, and dealing with the stop watch is too confusing given that you are also plotting at the begining and end of the 3 minute period. The Nomograph, on the other had, is fast and EASY. I can rest easy now, confident that tomorrow will be a
bad day for the
bad guys.