I would:
*enable manual input
*Set bearing (first dial) to 180*
*Set Angle on bow to 90* if the destroyer is going from right to left as you look at it or to 275* if is is going left to right
*Set the speed to 14knts
*Have a wild guess at the distance
*Open the tube (must be a torpedo type that does not leave a trail)
*Set the detonation as magnetic and run it 1.5m below the keel (more if its rough water
*Wait until the destroyer is at your 180*
*Fire
*Pray
__________________
|