End around should NEVER be done submerged. Neither should patrolling during the daytime. The first principle of combat is that your batteries must always be fully charged, ready for a long combat.

So your end around must be done surfaced, at a range of at least six miles from the enemy. If your batteries are not fully charged during the end around you will lose at least a knot of speed, and that can spell the difference between getting a favorable position in front of the enemy and waving as they sail by. And you should get back to the target track out of sight of the enemy: at least six miles in front of them. If you have your tactics right, you're in that position so that they won't run over top of you until after sunset.

Then you have all night to decimate the convoy. Don't get greedy. Don't let the escorts pin you down. YOU are forcing them to play your game. NEVER play theirs. Hit and run all night.

Hello Rockin Robbins,

of course i always did the end around technique surfaced, unless i wanted to catch a single merchant ship that was running away.

When the convoy approached me i tried to position my submarine accordingly, so i was a smaller target for the enemy sonar just as written in the TMO 2.5 manual. Thanks to that, i was able to start my attack being undetected by escort ships.

When the escort started dropping depth charges on me i dived to a secure depth and waited there on engine off and run silent mode. Most of the time i received no damage at all. I deployed decoys when available to distract the escort. I waited few hours submerged till sunset to be sure that i will be safe when i surface. Usually i sunk 1 or 2 merchant ships from every convoy that i intercepted starting from late 1943. Once i sunk 3 ships from 8. One time i came across an unguarded (?) 8 ship convoy from which i sank 6 (!) ships, because i run out of torpedoes in forward torpedo room and those 2 remaining ships were heading to enemy port through shallow water. I tried to avoid intercepting convoys in shallow waters.

In total i sunk ca. 200 000 tons in my RSRDC career that lasted from 16 June 1942 to 15 August 1945. However, in the RSRDC You will have less ships to encounter than in the stock game. For example: a SH4 Let's Play Youtuber that played stock SH4, sunk about 1 000 000 tons (!) from 7th December 1941 to the end of the Pacific war.

Having done it (with the help of radar which makes it much easier), I have to admit that sinking a ship blind is very rewarding, but how realistic is it that a skipper would sunk an unidentified ship?

Maybe in certain locations the vessel would likely be a valid target, but even then, how would know it wasn't a hospital ship, or neutral? Did any skippers attack unidentified targets In the Pacific?

I agree with what Rockin Robbins said. In RFB/RSRD I find 5 miles distant from the target is sufficient to stay out of sight.

You could fire blind based on the fact that the passive sonar gives you the first sound on any target at exactly +/- 10degrees from it's actual bearing. Just set the hydrophone at 10degrees ahead of where you want to fire, and wait for the green light to come on, then go shoot.

"Even aiming with periscope is hard and i am loosing (LOSING) the sight of my target, so firing torpedoes is simply a waste"

In real life if the waves were high, SOP was to decrease periscope depth to compensate. Standard periscope depth 66 feet was used when the target was close, at 15,000+ yards they would routinely go to 60 feet or less - 10 feet of periscope sticking up would not be a problem since it wouldn't be visible at long range. Same applies to heavy seas, especially with a lot of whitecaps, manually selecting 40-45 feet works just fine, even inside of 2000 yards. Rule of thumb, if the waves break over the periscope and you can't see anything but water more than 50% of the time, bring her up a couple feet.

As for attacking unidentified targets, subs on both sides were usually given a patrol area in which ALL targets were assumed to be enemy - the Germans in particular issued warnings to all neutral countries about "exclusion zones" where any ship might be attacked without warning, enter at own risk.