[joegrundman]

OK Let me explain. The transparent arm with the yellow boat symbol should be fixed to the wheel marked Lage so that the yellow boat always sticks out from the 0 position of the Lage wheel. If this is difficult to implement, you can always just remove the transparent arm with the yellow boat. It is no great loss.

One other minor-ish feature is that the front of the Submarine is represented on the largest wheel by a small triangle, just next to the 180 mark. you can see it at the bottom of the image.

To make the wheel more intuitive you might reverse the outermost wheel so that the front of the submarine is at the top.

The primary function of this wheel is to solve the problem of target course (although it has other functions too)

This is how to do it:

First, set your current true course on the yellow wheel so that your course is indicated by the small triangle.

Second you rotate the long thin arm, which represents your line of sight, so that one arm strikes the current relative bearing to the target on the outermost ring (i.e. the periscope view).

On the opposite side of the arm, you can read off the true bearing from North to the target on the larger of the two scales on the yellow ring. This can be immediately used for plotting.

NExt turn the wheel on the Lage ring to so that the AOB thta you have determined strikes the long thin arm. The pointer on the Lage ring, at the 0 mark, indicates the target true course.

Alternatively if you already know the target true course, you can use it to determine AOB for any given perisocpe bearing.

The last ring is the funny shaped vorhalt ring. This hasn't much use. I believe it's for manually marking your torpedo firing point when you don't have a TDC working.

I'll write about the slide rule later, but really a slide rule has a thousand functions