[Bosje]

I tend to do this:

draw a line along the reported course and then get the compass tool. draw a circle extending to a maximum of 100-150 kilometers. set a course at full speed to the edge of that circle where you expect the convoy to be. that is the first course change.

then, as the boat is speeding up (maybe those extra minutes will prove vital), give it a closer look.

draw 2 lines from the reported convoy to the edge of that circle. rougly 20 degrees to either side of the projected course, this leaves you with a projected search area in a roughly 40-45 degree margin of error around the reported course

I hope this makes sense so far.

then you look at the speed of the target, the report should give the estimated speed, or else you will know it is slow (around 6kts), medium (around 8-9kts) or fast (never seen that happen so far on convoys)

you calculate when the convoy can reach the outer limits of your search area, make sure you are there earlier and draw 2 cirlces with a diameter of 30 kilometers. these should overlap or almost overlap. also draw a 30 kilometer circle on the reported course

then you time the whole thing. always get there as soon as you can, hopefully reach the first intercept point before the convoy travelled more than 100 kilometers. you then have 3 positions where you can spend some minutes listening on the hydrophone (listen yourself with all engines stop at a depth of around 20 meters), don't depend on your sonar operator

if you travel between those search positions fast enough during the hour or so which the convoy needs to travel through the search area, you really should be able to hear the screws on the hydrophone. even if no lookout reports a ship or the sonar guy doesn't report any contacts

did that make any sense?