That's actually the fixed wire method that BillCar explained earlier. Except that you don't really need to be motionless for it. Just not turning, and have the periscope pointed dead ahead (0), or astern (180). Other than that it's the same.

Not quite the same. With the method I use I can be sitting at 90 degrees and ahead of a targets projected path allowing me to take several speed measurements in a 120-degree field (approx.)

I originally used the 0-ahead and 180-stern method, but would find myself repositioning the u-boat just prior to the attack, and sometimes due to the target's speed it may pass by my perfectly lined-up attack before I could get realigned. I don't need to do this any more.

Thanks you lot, you,re a great bunch of submariners ,I,ll drink your health at my Local H:)

Ok, but then you need to be pretty sure you are not moving. Any forward speed on your part will distort the speed of the target. 1 knot of you, with the target at bearing 60/300, means the target speed reading is short by 1.7 times as much. The more he is to your beam, the worse it gets.

Which is why I stated you need to be at 0 speed and, as in real life, you don't rely on just one speed measurement but take several as your target approaches.

With this method I achieve very accurate speeds and have been able to hit convoys at very long range without having to reposition my boat each time. The additional benefit of course is there are no engine noises to pick up as I try to get into position to take the next set of measurements.

I've tried various methods over the years like 0-ahead, the 3.15 minute track and nomograph but this has proven the most effective for me.

@Hardigen, as you can tell from reading this forum there are many ways to measure speed, distance, AOB etc. Its worth trying out various methods and you'll eventually find one that's right for you too.

Good hunting! :)