Das Boot and helpless subs

Factual Questions
41

[QUOTE=matt]
While this was certainly the case on post WWII diesel electric submarines, the U-boats did utilise direct drive.

From REPORT ON THE GERMAN SUBMARINE OF THE U-570 CLASS CAPTURED BY THE BRITISH IN AUGUST 1941, Section II-C-1:
“The drive is direct connected diesel. The chief engineer stated that switching arrangements are provided so that one engine can drive its own propeller direct, and, with its motor operating as a generator, drive the other propeller by electric drive.”
[/QUOTE]
Indeed. Those WWII U-boats were exceptionally flexible in their engine/motor/propeller configurations, with two diesels, two e-motors (doubling as dynamos) and two propellers, all linked by gearing.

One of the most effective methods of conserving fuel on long voyages, which enabled Type VII boats to participate in the Operation Drumbeat attacks on the east coast of the USA, was to run on one diesel on the surface. When the batteries needed recharging, the other propeller could be used to run the second electric motor as a dynamo, the power coming from the screw turning passively in the water as the boat moved. That was discovered by the boats’ engineers, not the boffins back home.

Another interesting feature was reverse “gear” on the diesels. That was achieved by briefly stopping the engines and shunting the cam-shaft so different cams were engaged, reversing the valve timing. With a skilled engineer, that only took a few seconds to achieve. To this day, many tugs employ the same principle. But I digress.

42

I just caught DAS BOOT (on AMC). man, life on a U-Boat wasn’t fun! Regarding max. safe depth" the depth gauge stopped at 250 meters 9about 750 ft.)-that seems awful deep! anyway, once a leak started 9at such a depth0, could it ever be stopped? they showed guts ramming spikes into leaking pipes-I doubt that would do much good at 750 feet! Oh-and the return to Kiel was heartbreaking-the weary crew gets back home (greeted by Adm. Doenitz), only to come under allied air attack! As i say, service in the german subs wasn’t very much fun.

43

[QUOTE=ralph124c]
anyway, once a leak started 9at such a depth0, could it ever be stopped? they showed guts ramming spikes into leaking pipes-I doubt that would do much good at 750 feet!
[/QUOTE]
Damage control is an art and a science. You’d be surprised what you can do, even against tremendous pressure. In DC school, I did a soft patch (wooden wedge, rubber gasket, soft iron gromet, marlin wrap) on a linearly-ruptured pipe that held pressure (dry) to 900psi, and only started to leak-by (slow drip) at 1000psi.

You simply need to know what you’re doing. And know how to do it in a hurry. And not panic.

There’s a reason the boat crews are highly selected and elite.

44

[QUOTE=ralph124c]
anyway, once a leak started 9at such a depth0, could it ever be stopped? they showed guts ramming spikes into leaking pipes-I doubt that would do much good at 750 feet!
[/QUOTE]

I can’t speak for the spikes. I think it would work, if for no other reason than it forces the flaw into the shape of a circle which makes crack propagation much less likely, which is what the real killer would be.

ETA: I was thinking metal spikes, not wooden ones - a wood insertion is going to mold itself to the flaw, not mold the flaw to it. Which is another advantage, as Tranquilis mentions.

As for leaks? All submarines leak. Hell’s bells, all ships leak. That’s why bilge pumps are a necessity for anything in the water. As a general rule of thumb, any penetration through a bulkhead, or hull plating, will leak if there’s water on one side, and air on the other.

A modern submarine will be designed to minimize those hull penetrations, but they can’t be eliminated. And AIUI WWII boats had more penetrations than modern hulls do. For-ex, I think that all navies, during WWII, had each head discharging directly overboard. Which is definately not the case with modern US subs.

The source of the leak is going to matter a lot more than you might think, too. A failure in an inboard pipe will offer a number of potential ways to isolate, or at least minimize the leak. A failure at the hull penetration itself is another matter, but because welds are often stronger than the formed metal around it, can often be counted on to resist crack propagation - if there are ways to ameliorate the stresses.

AIUI, cracks in the hull plating itself is a very, very bad thing - in part because there’s nothing to prevent crack propagation.

45

Metal spikes aren’t out of the question - they can be used to shape the rupture, as you note, either to plug directly (though I’ve never heard of a direct metal plug, it could be made to work), or to shape the opening to accept a soft wood plug, or to fair the lips of the rupture to allow other kinds of patching to take place.

In general, there are a number of means for controling a ruprure: Cut it off via valves is the first and most desireable method, then weld the hole shut if you can. Failing that, an Adams or Mormon Clamp would be a good choice, or failing that, strap a strongback to it. Or if you can’t get a strongback in place, used a soft patch. Along the way, you’ll want to do everything you can to minimize the flow through the rupture, minimized the area of the rupture, and smooth the edged of the rupture.

Methods for reducing surface area includes pounding any raised lips back down (also smooths lip edges - bonus!) with mallets and hammers, fitting appropriate-sized wedges and plugs into the gap, and so on. The plugs and wedges are then cut off flush with the surface, and the remaining patching techniques are put into play.

Once all leaks are stopped, you can take a look at restoring some systems to function with more perminant repairs. Bypassing, welding, brazing, clamps, plastic (fibreglass) patches, strongbacks, and yes, even the soft patch, may all be used to restore a damaged system to some level of functional utility.
edit:
Damaged structures can be shored up by a number of means, including wooden beams, expandible metal shores, or whatever improvised method seems mostly likely. This is art and science backed by many hours of practice, backed by years of experience.

Hull ruptures can have box patches welded (for metal boxes) or shored (of wood or metal) into place, or mattresses can be shored into place, or mattresses can be faired over thehole from the ourtside, or even a good canvas tarp faired over a hole from the outrside, all can reduce incoming flooding to a degree that pumps can handle it. Those extermal measures, or course, require that no hostile force be nearby. If all eles fails, a space can be isolated by its watertight hatches, and thoe hatches shored up. That last, of course, is a desperate move.

46

[QUOTE=Barrington]
Another interesting feature was reverse “gear” on the diesels. That was achieved by briefly stopping the engines and shunting the cam-shaft so different cams were engaged, reversing the valve timing. With a skilled engineer, that only took a few seconds to achieve. To this day, many tugs employ the same principle. But I digress.
[/QUOTE]

Most ships are the same.

47

[QUOTE=Tranquilis]

Elite service. In the German (WWI, WWII) and American navies (early part of WWII), the submarines were the only part of the naval force actually putting any real hurt on the enemy. For the Germans, it would mostly remain so; The American surface fleet finally got its act together. But in the those days, boats were where it was at, if you wanted to take the fight to the foe. Sailors, like any fighting man, want to think that they’re doing something, accomplishing a goal. The boats were getting it done, and so had their pick of the fleet personnnel. That allowed the sub force to be choosy, making the units ‘elite.’ Once a unit is established as ‘elite,’ the story builds upon itself, making the unit that much more desireable, leading to more and higher-quality applicants, further allowing choosiness by the fleet, and reenforcing the ‘elite’ image.
[/QUOTE]

And, for some time, U-boot staff has the best of everything while in port, and much acclaim. I remember one U-boot autobiography where the Captain got ashore, and found his father had been taken in by the Gestapo for interrogation, as his Father had taken (and concealed?) a Jewish girl as a mistress. The Captain of a U-boot with Knights-Cross and all apparently had enough pull to walk into Gestapo HQ and walk out with his Dad, and even the feared Gestapo would not try to interfer with such a hero.