a question on VII depths

[Sag75]

Hi to all,


Let's take the VIIc....

Uboat.net states VIIc have max depth at 220,
GWX Help (F1) states max depth is 150,
I can reach 250... 255 is crush depth I guess..

So, what does it mean Max Depth? Is it the test depth? the project depth?


thanks in advance!

[Letum]

The max depth of 150m is the manufacture's warranty depth.

The deepest anecdotal depth for a VIIC is about 240m.
Apperantly the boat was near vertical at the time, so it's aft/bow may have been as deep as 275m

[Task Force]

yep, im in a viib, DONT GO PAST 220. lol:rotfl:

[Sag75]

The max depth of 150m is the manufacture's warranty depth.

The deepest anecdotal depth for a VIIC is about 240m.
Apperantly the boat was near vertical at the time, so it's aft/bow may have been as deep as 275m


Thanks,

I'm just curious about that anecdote.. the boat almost vertical ? :o How happened that?

[meduza]

Thanks,

I'm just curious about that anecdote.. the boat almost vertical ? :o How happened that?
Probably had the aft compartments full of water. :hmmm:

[Letum]

Thanks,

I'm just curious about that anecdote.. the boat almost vertical ? :o How happened that?

I can't remember now. I suspect meduza is right.
They ended up so deep because someone forgot to turn on a valve that turns
on the depth gauges in the control room and radio room.

Damm...wish i could remember where I read this!
I'll go on a hunt later...

Ed: I'm worried now that it might be Iron coffins. The author was a u-boat
commander, but he made a lot of stuff up. I'll check...

[Empty B]

U-331

Freiherr Hans-Diedrich von Tiesenhausen

Sinking of HMS Barham

http://www.uboatarchive.net/U-331INT.htm

"she submerged to about 250 m"

[Letum]

No, not iron coffins.
I strongly suspect I must have read something about U-175, but I can't think which book!

The U-boat archive describes what I read well:

http://www.uboatarchive.net/U-175INT.htm
At 1252Z, "Spencer" [a destroyer] made an urgent attack on the
U-Boat, firing a pattern of 11 depth-charges set at 50 ft. and 100 ft. This
was considered a hurried and inaccurate attack which was not believed to
have caused any damage to the U-Boat, except possible shaking up.) In
point of fact, damage was very considerable. "U 175," submerging to a
safer depth, was caught at about 65 ft., and it appeared to prisoners that
the depth-charges exploded beneath them. The following damage was
sustained: Fracture of the air trunking. Fracture to pressure hull between
forward torpedo tubes causing water entry. Bilge pumps put out of action.
Hydroplanes defective. Heads of Diesel engine holding down bolts snapped
off. The entire pressure hull strained so that watertight doors could not be
properly closed. Partial failure of lighting. Breaking of pressure, depth and
other gauges. The majority of the W/T equipment torn from its fastenings
and hanging loosely from its wiring. "U 175" now began to plunge downward
out of control, and some prisoners claimed that she had reached a depth of
below 900 ft [274.32m]. before trim was restored. Frantic efforts were
being made to repair the damage, and in the case of the air trunking this
was successful.
The leak forward was also found to be less serious than was at first
thought, and it was said that it was partially plugged.

[Graf Paper]

In GWX, you do get cues with pronounced creak, groans, and popping of the pressure hull as you go deeper. The louder and more frequent they become, the more stress on your boat.
Once you start to hear the squeal and whine of metal, you're definitely in the danger zone. A u-boat can only tolerate such depth for a while before the hull begins to fail.
By the time you hear bolts and fittings bursting along with the tinkle of glass gauge covers shattering, you have only seconds to react and raise your depth by at least 20 meters or it's straight to the bottom you go! :o

[Schroeder]

No, not iron coffins.
I strongly suspect I must have read something about U-175, but I can't think which book!

The U-boat archive describes what I read well:

http://www.uboatarchive.net/U-175INT.htm
It is odd that a sub with a broken pressure hull should be able to go that deep. :hmm2:

[Letum]

Would it not be even stranger if it went to such depths undamaged? :know:

[Schroeder]

Sure, but I wonder that a breached pressure hull could withstand that enormous depth. I mean imagine how deep an undamaged sub should be able to go if a damaged one can reach ca. 275m.
Sounds a bit odd to me.

[john doie]

Correct me please, 'cause I have been living under Hollywood special efects for a while, but a submarine doesn't behave as an aicraft. A fracture in the pressure hull is not instantly fatal. It's seriousness depends on depth, on metal strenght and placement. Water would be forced in at great pressure, but it is a fissure in the metal skin. With time, pressure and water, it will grow bigger, but if water is pumped out of the boat as fast as it gets in, and if the boat is brought to a safe depth, it will survive.

This will illustrate what I mean> http://www.youtube.com/watch?v=2ip1bv3Y4_A

[Schroeder]

Yes, but what happens if you apply pressure with a pencil on a piece of clothes for example? it can withstand the pressure for some time but if it grows too strong it will be pierced and then your pencil can open the hole easily. The same happens with a pressure hull. If it is intact it can take a lot of pressure but if there is a hole in it the area around the hole will become pretty weak and give way. (at least that's what I'm thinking but maybe someone here has better knowledge of that)

[john doie]

Yes, it gives way, but not in a second. It takes time. It is related to the internal structure of the metal that makes the pressure hull. A fault in the metal can doom a submarine. Pressure does the rest. It also depends how much pressure is applied, and for how long. Too much pressure, like 300+m depth will work faster then 210m depth.

What I am trying to say is that pressure is forcing water in and pushes against the pressure hull. In order for the hull to fail, it needs to fail at resisting the push from pressure, not at failing to prevent water from comming in (with the mention that water comming in has to be equal or lower with water pumped out). So this bring us to the point where that crack causes a fail in the pressure hull. If it doesn't, all is ok ... for the moment.

http://www.youtube.com/watch?v=MJRFySv0fv8&feature=related
Look at this. The beam first bends, then cracks, and lastly fails. It takes aditional pressure before a weakened structure fails. Same is on pressure hulls.

[Melonfish]

i'm sure they touch on this in Das Boot too (the book) about the fact that they didn't open a valve so kept flooding the tanks and whatnot thinking they weren't leaving the surface?

as for crush depths i've never been deep enough to get smushed except once when i flooded heavily and ended up on the bottom trying to repair frantically.
3 blows of compressed air later and alot of pumping and we slowly started to rise again.