Deepest I've Ever Gone...Think It's A Subsim Record
 

Playing SHIII, mucking around the Western Approaches in late 1944 in a Type XXI. It's a little before midnight, and we've surfaced to air out the submarine and charge the batteries after running submerged halfway through the Denmark Strait due to the constant patrols of Allied bombers.

While we're traversing the slightly choppy waves, I hear a loud, too-familiar buzzing. For the first time in all of my SHIII campaigns, I get illuminated by a flight of Short Sunderlands (I believe) carrying the Leigh Light. Having only my secodary watch crew on station, we didn't see them until it was too late.

I immediately order all hands to action stations and a full crash dive as the first few depth charges go off, far over to starboard. The U-2507 makes a hard turn to port in response, just passing 25 metres now. However, a second pass by another Sunderland must have bracketed the sub, and flooding begins in both engine rooms.

I send the damage repair crew, already busy so far this patrol, on station to fix the most serious flooding in the sternmost engine compartments, praying that the pumps can hold out long enough in the diesel room for the damage controlmen to get there in time.

At this point, some 50 metres down, I give the order for the sub to level out and slow to ahead full as depth charges continue to go off overhead. Standing in the control room, however, I notice that the needle on the depth gauge seems to be edging steadily towards 100, and the ship seems to be tilting.

To make a long story a little shorter, we get down to 230 metres by the time the electric engine room is fixed and the intake of water has ceased. The damage crew immediately starts work on the damage to the diesels, but the ship has only slowed her descent.

By now, the helmsman is frantically keeping myself and the rest of the crew aware that we've long passed critical depth...260 metres. The glass on almost every instrument has broken, and the creaking of the submarine is getting a little too loud for comfort as all available hands work furiously on getting the water out of the compartments.

Finally, at 314 metres, after the lights have gone out and left us in total darkness, repairs are completed. Hoping the British are gone, I blow every bit of compressed air out of the tanks and U-2507 shoots for the surface. At 2347 hours, we breach the surface of the water and exit the submarine to survey the damage-a gaping hole and scorched metal along the aft of the ship.

I don't know how we survived, but as of right now, we are making for Trondheim, taking the most northern route available in an attempt to avoid patrols of any sort. I have given strict orders that the submarine is not to go below 25 metres.

After that harrowing experience, I think we'll settle for that lone liberty ship.

Wow~! What is the so-called Max Depth rating for Type XXI?

Good read. I like when I get in situations like that. I don't often survive but they're still fun.

The max depth rating was supposed to be a comfortable 1200 feet. But because the type XXI was rushed through production in prefabricated sections in factories that had little or nothing to do with shipbuilding, the quality of the final build was always dubious. The British tested captured XXIs and found hull failure at 800 feet, and the Germans tested 900 feet. But in all cases, the pressure hull was much weaker than should have been, and provided no more depth than the (then current) type VII or IX.

Was about to post that exact same thing...you know your stuff! Type XXI's were notorious for quality control problems....in a lot of ways, they were like the UB-III boats Germany rushed out towards the end of WWI. Technically good units that suffered badly from material shortages, plus mediocre workmanship.

I'd still take a type XXI over a Ford Pinto any day!!!

Hahaha!
Basically a fuel tank inside one big crumple zone...

I also found out that this overall failure was liberally distributed​ across many systems.
The American evaluation team that went over the captured U-2513 found a few desirable features (bigger battery storage, improved periscope optics and underwater sensors, improved snorkel design), but quite a few design flaws that call the actual combat worthiness into some doubt. These included the hydraulic lines which actuated the dive planes, AA turrets and snorkel, were outside the pressure hull and were vulnerable to both salt water corrosion, as well as depth charge shock damage, and needed the full services of a shipyard to repair. The diesel engines were poorly designed and built with substandard materials that the geared supercharger could not be used, which cut the potential HP in half, leaving the type XXI ruiniously underpowered. The snorkel system let constant streams of water into the bildge which had to be pumped outboard, which spoiled their stealth.
In all it's been said that even if the type XXI had come on line into mass production a year earlier, it would not have had such a significant effect on the war effort.
Maybe if they started from 1940/41 would it have made some kind of difference...

I hope that was not a live test.

The books I've read said "simulated depth test", but I'm not 100% certain of how. In the days before computer modelling, tests to destruction meant literally that. For example, in the mid to late 1950s, the British were losing "comet" jet airliners to an unknown cause. They put one of the air frames into a giant tank of water and started filling 'er up. Finally the hull failed and that's when they discovered that the square window frames were putting too much stress on the structure, from the constant pressure changes, and from that point on, (as you can see this today) all aircraft that operate at altitudes over 10,000 feet have rounded window frames.
I assume something similar was done to test surrendered​ or captured U-boats

Eh, they probably just tied a rope to one and pushed it over the side. When the rope either stopped and came back up (sans sub), or started feeding out real fast, they knew it failed. :Kaleun_Cheers: