Tactics question (100% realism)

[plj]

Ok, so my first mission directs me towards poland to sink a taskforce ... no issues finding it .. get out of harbor, flank it and set course 243, wait till about 10 pm, go to 20, engine stop, take a few bearings, plot intercept and soon we have smoke on the horizon.

But, the nasty buggers are doing a zig-zag ... now I could try to get to a 90 degree angle, except that they alter course all the time as well on their patrol. How does one tackle this situation ?

Do I get so close that it is going to be impossible to miss ? Is there a way to take this zig zag into acount ? Is this what spread is for ? (seems so wastefull) I could use a pointer ...

I play on full realism, with real navigation.