[propbeanie]

As it stands now, if a ship is traveling appoximately 1/2 of its rated top speed, then you won't be able to "see" them on sonar yourself. Your sonarman does, but not you. CapnScurvy is working on a solution, and there ~might~ be a fix, but it may well be complicated. We'll see. Another thing to remember about this particular issue is that as a ship turns, it loses speed, scrubbing 3-5 knots off of its speed. If you ever depart from Pearl and see the inbound ships, some of them are set to 12 knots, just so that they'll traverse on through all the curves in the harbor.

As for the radar, you don't get the periscope mounted one until late in the war. The "contacts" you see via radar flash on and off to simulate the rotation of the antennae. Once you make "visual" contact, your radar and / or sonar no longer show the contact - not needed (supposedly).