[XLjedi]

Let's just make it really simple...

Forget the O'Kane method. It's just a way to make the TDC point close to a 0° gyro angle anyway, and if you're always going to take up a 90° position abeam the target true course, you might as well just ignore the TDC completly and just sail out of port with the default 0 speed 0° bearing settings. Ever accidentally launch a fish in port and notice how it swims straight out the bow of the sub? ...that's a perfect 0° gyro shot.

All you need now is the lead angle to position your aiming wire for various target speeds. A simple thumb-rule formula for a Mark18 doing 30kts aimed at targets traveling between 6 and 12kts would be: =2*S-1

That's 2 times the target speed minus 1. So for a ship doing 6kts its: 2*6-1 = 11°

So with a 0° gyro setting (torpedo swims straight) I'm in position (90° abeam the target course). The target is moving at 7kts. So I point my aiming wire at 2*7-1 = 13° and I wait. As a target point of interest passes my aiming wire (perhaps the smoke stack), I mash the launch button. ...fish swims out and smacks the target right under the stack.

Obviously, if the target approaches from the right, I'm leading 14° to the right (0+14 = 14°). If the target approaches from the left I'm leading 14° to the left (360-14 = 346°).

If you're using a torpedo with a different top speed, just give me the torpedo speed and I'll figure a new formula. I think there's a chart already done that has all the lead angles for various topedo/target speeds.