WWII U-Boat internal pressure question

[J]

This ignorant civilian would like to know why a U-boat, forced to
remain
submerged for a long time, would develop excess pressure.

Background: I'm currently reading "Hitler's Admirals" by G.H. Bennett
and
R. Bennett, a U.S. Naval Institute Press book (2004) [ISBN
1-59114-061-7].
It is "based on extracts from English translations of essays written
at the
request of British Intelligence by nine German admirals who were
prisoners of war in British hands in 1945" according to the preface
(p. vii).

Grand Admiral Donitz (p. 71) writes "... the result of the U-boat
activity was
extraordinarily disappointing. The chief reason for this was torpedo
failures.
If a torpedo shortage had been evident in the early months of the war,
it
was now their ineffectiveness in the Norwegian expedition that became
disastrously apparent. As a result of being in contact with the enemy
for
long periods, the U-boats were forced to remain submerged for a very
long
time, causing excess pressure in the boat, which penetrated the depth
chamber of the torpedo and considerably increased the depth
setting. . . .
[snip] The reason for the increasing number of torpedo misses was
only
understood by the German navy at a very much later date, when the
individual technical faults of the torpedo were ascertained by
systematic
testing.

Thanks . . . J

[J]

Sorry I botched the line length on the previous post. I use Google
Groups
and it now creates long lines. I was trying to shorten the lines but
got it
wrong. I apologize for an inconvenience.

Cheers . . . J

[J]

D*mn! Did it again.....sorry!! I give up.

[David E. Powell]

On Apr 12, 1:35 am, J <emer...@excite.com> wrote:
> D*mn! Did it again.....sorry!! I give up.
>
> Cheers . . . J

I have heard some WW2 subs actually compacted a little at depth from
the pressure. That might cause a slight overpressure in the boat. Not
enough to cause health issues with crew but maybe enough to annoy
sensitive torpedo gear, membranes, etc.

Putting a little "pressure in the boat" to check if hatches were
sealed was a common practiec in US boats, too. Maybe the Germans did
the same thing.

[Harry Bennett]

There will always be small leaks from internal systems, mainly air, and
this causes the internal pressure to rise over time. There may also be
systems, tank blowing etc, that use air and vent inboard.

A surfacing officer of the watch learns this the hard way as he gets
lifted up the tower when he opens the hatch.

Harry

[Paul F Austin]

The torpedo-firing mechanism uses a large cylinder that contains a
floating piston. On one side, water is forced into the rear of the tube
to expel the torpedo. The other side of the piston is driven by high
pressure air. After firing, the air is vented inboard to return the
piston to battery, refilling the water side through the now-empty tube.
The vented air would accumulate until the next time the boat surfaced,
which for a WWII boat wasn't a very long time. Given the short time
submerged, I have trouble seeing how very large increases in air
pressure could occur.

Paul

[Eugene Griessel]

Yet you read in several autobiographies of submarine skippers of WW2
vintage of having someone hang on their legs when they opened the
hatch after a torpedo firing to avoid being blown out.

Eugene L Griessel

History: An account, mostly false, of events, mostly unimportant,
which are brought about by rulers, mostly knaves, and soldiers,
mostly fools.
- Ambrose Bierce

[Keith W]

Even a modest 1 psig increase in pressure translates to a lot of
force on a 20" hatch

Keith

[Eugene Griessel]

On Thu, 12 Apr 2012 19:47:10 +0100, "Keith W"
<keithnosp...@demon.co.uk> wrote:

>Even a modest 1 psig increase in pressure translates to a lot of
>force on a 20" hatch

I dont think they were worried about the hatch - but about being blown
overboard through the hatch.

Eugene L Griessel

To steal ideas from one person is plagiarism;
To steal from many is research.

[John Szalay]

Eugene Griessel <eug...@dynagen.co.za> wrote in
news:cfbeo79us3mllt11p...@4ax.com:

> On Thu, 12 Apr 2012 19:47:10 +0100, "Keith W"
> <keithnosp...@demon.co.uk> wrote:
>
>>Even a modest 1 psig increase in pressure translates to a lot of
>>force on a 20" hatch
>
> I dont think they were worried about the hatch - but about being blown
> overboard through the hatch.
>
> Eugene L Griessel
>
>

IIRC:
when the US boarding party got onto the U-505, they found the hatch closed
and could not open it, they grabbed a U-boat crewman from out of the water
and he showed them a release valve to release the pressure , they, then
shoved him back off the boat, with a "Thanks Bud !"
and then went below.. to salvage the boat.

[George152]

I understand that that was the cause of a few impatient captains coming
in contact with the metalwork.
The urban legend says that some were lost over the side

[Eugene Griessel]

Got this on a website not far from here:

13 July 1945

1800 #4 motor brushes and rigging installed and brushes sanded. Have
renewed 63 out 96 brushes, but we are one brush short of total
originally installed due to burned brush holder. Surfaced with about 3
inches pressure in boat. Conning tower hatch was opened and Commanding
Officer had started up when lower conning tower hatch opened due to
the one dog dogged on it being wedged open by the pressure. Commanding
Officer floated up hatch banking off hatch wheel with face suffering
two one stitch lacerations on head and chin and a lesser cut on
eyelid.

Eugene L Griessel

Adults no longer believe in the Tooth Fairy - but they still torture and
kill each other over ancient myths and superstitions.

[Weatherlawyer]

On Apr 12, 8:42 pm, John Szalay <john.szalayATatt.net> wrote:
>
> IIRC:
> when the US boarding party got onto the U-505, they found the hatch closed
> and could not open it, they grabbed a U-boat crewman from out of the water
> and he showed them a release valve to release the pressure , they, then
> shoved him back off the boat,  with a  "Thanks Bud !"
> and then went below.. to salvage the boat.

I doubt there was much love lost but even had they been more kind, I
don't think they would have wanted unfriendlies around on such a
delicate expedition.
Do you?

I should think they had no men to spare watching a prisoner. Previous
experience in capturing U-boats was that the descendants were usually
ancestors before the ship's boat got back with the prezzies.

[Dan]

On 4/12/2012 12:34 PM, Eugene Griessel wrote:
> On Thu, 12 Apr 2012 19:47:10 +0100, "Keith W"
> <keithnosp...@demon.co.uk> wrote:
>
>> Even a modest 1 psig increase in pressure translates to a lot of
>> force on a 20" hatch
>
> I dont think they were worried about the hatch - but about being blown
> overboard through the hatch.
>

Well, the pressure is released through the hatch after the hatch cover
is opened. Assuming the person is obstructing the hatch opening, the
pressure is releasing but also pushing on said person.

Dan

[John Szalay]

Weatherlawyer <weathe...@gmail.com> wrote in

>> and he showed them a release valve to release the pressure , they,
>> then shoved him back off the boat,  with a  "Thanks Bud !"
>> and then went below.. to salvage the boat.
>
> I doubt there was much love lost but even had they been more kind, I
> don't think they would have wanted unfriendlies around on such a
> delicate expedition.
> Do you?
>

Nope,,,

[peter skelton]

"John Szalay" wrote in message
news:XnsA033A03DF3B6B...@216.196.97.142...

How did the Germans get out of the boat without releasing the pressure?

AMazon has bs detectors on special this week.

Peter

[Jeff Crowell]

John Szalay wrote:
>> IIRC:
>> when the US boarding party got onto the U-505, they found the hatch
>> closed
> and could not open it, they grabbed a U-boat crewman from out of the water
> and he showed them a release valve to release the pressure , they, then
> shoved him back off the boat, with a "Thanks Bud !"
> and then went below.. to salvage the boat.

peter skelton wrote:
> How did the Germans get out of the boat without releasing the pressure?
>
> AMazon has bs detectors on special this week.

I confess I had the same thought, but OTOH you'd expect a
boat that's been damaged badly enough for the crew to be
willing to go for a swim might have had its usual allotment
of air leaks significantly enhanced by said battering.

The REAL question is, why did they shut the door behind
them? But people do odd things under stress; had the same
thought recently while watching tsunami footage taken during
last year's watery catastrophe in Japan. The video was
taken by a fellow who spent a while using his car as an
impromptu boat (and survived, which is the really amazing
part). The driver of the car in front of him, as the water
starts to swirl around the cars, jumps out of his car, runs
out of shot, then dashes back in just long enough to close
the door of his car before bolting back out of view again.
Pretty amazing.


Jeff
--
Every path has a few puddles.

[John Szalay]

"peter skelton" <skel...@yahoo.ca> wrote in
news:jm7tih$6dq$1...@dont-email.me:

May I suggest you Read Adm Gallery's book,

they removed the cap of the scuttling pipe, but did not set the
explosives charges to blow up the boat, when they abandoned ship
apparently they closed the hatch, probably to keep the boarding party
out. most likely the water rushing in from the pipe raised the internal
air pressure.

Just read the book..cheaper than any BS detector !

.

[Eugene Griessel]

On Fri, 13 Apr 2012 07:33:44 -0500, John Szalay <john.szalayATatt.net>
wrote:

There would have had to be a vacuum in the boat to make the hatch
difficult to open. Pressure in the boat would have meant the hatch
would have flown open as soon as the dogs were off it.

Eugene L Griessel

The difference between genius and stupidity
is that genius has its limits.

[peter skelton]

"John Szalay" wrote in message

news:XnsA034576DF9A7A...@216.196.97.142...

Gallery never let truth get in the way of a story, especially one that made
him look good.
No BS detector made could handle his book as input.

Do you believe GI Joe comics too?

[Jeff Crowell]

Eugene Griessel<eug...@dynagen.co.za> wrote:
>> There would have had to be a vacuum in the boat to make the hatch
>> difficult to open. Pressure in the boat would have meant the hatch
>> would have flown open as soon as the dogs were off it.

Fred J. McCall wrote:
> That was the thing I immediately questioned. Pressure hatches are
> constructed so that the door opens into the 'high pressure' side. That
> way the pressure causes the door to seal better rather than unsealing
> it. So pressure hatches on submarines open OUT of the boat, because
> you want them to seal from water pressure when dived.


Yabbut, what if the air pressure in the boat is such that the
dogs are jammed? Pressure could be enough to slightly lift
the hatch in its seat without gapping the gasket, which could
put a side-load on the dogs.

Just sayin'.



Jeff
--
Live simply. Love generously. Care deeply. Speak kindly. Leave the rest
to the cosmos.

[John Szalay]

"peter skelton" <skel...@yahoo.ca> wrote in

> Do you believe GI Joe comics too?
>
>
>

Nope.

and as always

opinions ,
everyone has one and they all stink

[Weatherlawyer]

On Apr 13, 6:00 pm, Fred J. McCall <fjmcc...@gmail.com> wrote:
>
> Then you just use a longer pipe.  Looking at how dogs are designed, I
> don't think it's really possible for them to 'jam' and the door to
> remain sealed and intact.

If you have your book open, see if you can understand why the release
valve in on the out side.

[peter skelton]

"Weatherlawyer" wrote in message
news:c549652f-5f3d-4588...@m16g2000yqc.googlegroups.com...

So the guys on watch can open the hatch when they need to go below in a
hurry.

[Dan]

Except the pressure pushes on the hatch cover, which in turn pushes
against the closed dogs, which in turn make turning the dog-release
wheel harder to turn (enough pressure, impossible for a human). Given a
few inches of water (2 inches per psi) and a large surface area of the
hatch cover, the actual total weight on the hatch cover could have been
quite significant (thus the pressure release venting handle).

Nothing sounds fishy so far...

Dan

[Eugene Griessel]

Op Tue, 17 Apr 2012 09:02:35 +0100, Jeff <je...@jsystems.com> wrote:

>
>>
>> Except the pressure pushes on the hatch cover, which in turn pushes
>> against the closed dogs, which in turn make turning the dog-release
>> wheel harder to turn (enough pressure, impossible for a human). Given a
>> few inches of water (2 inches per psi) and a large surface area of the
>> hatch cover, the actual total weight on the hatch cover could have been
>> quite significant (thus the pressure release venting handle).
>>
>> Nothing sounds fishy so far...
>>
>> Dan
>

>Think your conversion factors are our a bit, 33 feet of water = 1
>atmosphere = 14psi approx. 2 inches is about 0.072 psi.

It's also a bit odd that submariners who wish to scuttle their boat
would close the hatch. They live in a boat where the saddle tanks are
permanently open at the bottom and only kept full of air by the valves
at the top being closed. So they would know about trying to flood a
closed vessel from the bottom.

Eugene L Griessel

Morality is unique and universal. Nothing is added to it and nothing
changes during the course of time. It is not dependent on economics,
history, sociology or culture; it is not dependent on anything. Not
determined - it determines. Not conditioned, it conditions. It is,
in other words, absolute.

[David Lesher]

Eugene Griessel <eug...@dynagen.co.za> writes:

>>>

>There would have had to be a vacuum in the boat to make the hatch
>difficult to open. Pressure in the boat would have meant the hatch
>would have flown open as soon as the dogs were off it.

Err, would not pressure increase the force on the dogs; keeping you
from moving them {easily}?
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[David Lesher]

I recall the Lunar Module also had a relief valve on its hatch.
Guess that was better than depending on propping the door open.

[Eugene Griessel]

Op Fri, 8 Jun 2012 14:51:49 +0000 (UTC), David Lesher

<wb8...@panix.com> wrote:

>Eugene Griessel <eug...@dynagen.co.za> writes:
>
>>>>
>
>>There would have had to be a vacuum in the boat to make the hatch
>>difficult to open. Pressure in the boat would have meant the hatch
>>would have flown open as soon as the dogs were off it.
>
>Err, would not pressure increase the force on the dogs; keeping you
>from moving them {easily}?

I don't think so. I have no idea what the hatch closing mechanism on
a U-boat looked like, I'll have to go and dig out a diagram to see if
that would be so.

http://www.blastitblasting.com/picsjan20/uboat%20hatch.jpg

is a fair picture of one. The mechanical advantage of the wheel and
levers would seem to imply that it might be a bit more difficult, but
I doubt it would become impossible.

Eugene L Griessel

Advertising (n): the science of arresting the human
intelligence for long enough to get money from it.

[Alex Potter]

Is that brass (?) fitting, on the right between the two latches, a
pressure relief cock or a drain?

--
Alex

[Eugene Griessel]

Op Fri, 08 Jun 2012 17:34:06 +0100, Alex Potter

No clue - I am still looking for a decent (annotated) diagram. I
somehow doubt it's a drain though. Too small.

Eugene L Griessel

Science is never certain. Scientific statements are merely approximates
with varying degrees of certainty. Evidence can increase the probability
that a statement is more likely to be true or false but it never makes it
absolutely certain one way or the other. - Richard Feynman

[Alex Potter]

On 08/06/12 17:38, Eugene Griessel wrote:
> No clue - I am still looking for a decent (annotated) diagram. I
> somehow doubt it's a drain though. Too small.

I hope you can find one. I thought that it was a bit on the small side
for a drain too.

--
Alex

[Eugene Griessel]

Op Fri, 08 Jun 2012 17:40:12 +0100, Alex Potter

What the photo does show - at the one o'clock dog - is a lug that
would prevent the wheel from turning but that would have to be engaged
by someone inside.

Eugene L Griessel

Though your mansion may contain 7000 rooms - at night you can only use 6 feet of space.

[peter skelton]

"Eugene Griessel" wrote in message
news:v574t7pld0ddtb6en...@4ax.com...

Op Fri, 8 Jun 2012 14:51:49 +0000 (UTC), David Lesher
<wb8...@panix.com> wrote:

>Eugene Griessel <eug...@dynagen.co.za> writes:
>
>>>>
>
>>There would have had to be a vacuum in the boat to make the hatch
>>difficult to open. Pressure in the boat would have meant the hatch
>>would have flown open as soon as the dogs were off it.
>
>Err, would not pressure increase the force on the dogs; keeping you
>from moving them {easily}?

>I don't think so. I have no idea what the hatch closing mechanism on
a U-boat looked like, I'll have to go and dig out a diagram to see if
that would be so.

>http://www.blastitblasting.com/picsjan20/uboat%20hatch.jpg

>is a fair picture of one. The mechanical advantage of the wheel and
levers would seem to imply that it might be a bit more difficult, but
I doubt it would become impossible.

They'd start cranking the diesels as soon as the exhaust back-pressure was
low enough, so any problem wouldn't last long.

[peter skelton]

http://www.uboatarchive.net/ has a lot of German manuals and translations,
much more than I've had time to look at

This from one included for kicks:

Remarks: It should be noted, that when pressure inside the boat increases,
the depth gauge not longer shows the real depth, but a lesser value,
relative to the pressure difference between water pressure and air pressure
inside the boat. That's why the depth should be also controlled by means of
the Papenberg column, periscope or conning tower flood valve.

[peter skelton]

"Alex Potter" wrote in message news:jqt9hu$78i$1...@dont-email.me...

It's a small test valve. It was opened as the boat neared the surface: if
water came in the boat was submerged, if air went out, it was surfaced or
very near the surface.

[Alex Potter]

On 08/06/12 21:06, peter skelton wrote:
>> Is that brass (?) fitting, on the right between the two latches, a
> pressure relief cock or a drain?
>
> It's a small test valve. It was opened as the boat neared the surface:
> if water came in the boat was submerged, if air went out, it was
> surfaced or very near the surface.

Thanks. Makes perfect sense that it should be a small as it is.

--
Alex

[Alex Potter]

On 08/06/12 21:03, peter skelton wrote:
> http://www.uboatarchive.net/ has a lot of German manuals and
> translations, much more than I've had time to look at

Thanks for that link - I'd forgotten that site existed.

The prisoner interrogation reports will make interesting reading...

--
Alex

[Vaughn]

I don't pretend to remember what type of depth gauges they actually used
in submarines (even though I'm an ex-submariner), but boat pressure
wouldn't necessarily affect the reading of a gauge, depending on the
design of the gauge. Most common bourdon-style gauges have their cases
vented to the atmosphere. In that case, what you say would be correct.

Other gauges have a sealed atmosphere inside the case. Those are not
affected by local atmospheric pressure.

look up the difference between PSIA and PSIG

A good place to start: http://en.wikipedia.org/wiki/Pressure_measurement

Vaughn

[ohar...@mindspring.com]

On Thursday, April 12, 2012 1:05:49 AM UTC-4, J wrote:
> This ignorant civilian would like to know why a U-boat, forced to
> remain
> submerged for a long time, would develop excess pressure.
>
> Background: I'm currently reading "Hitler's Admirals" by G.H. Bennett
> and
> R. Bennett, a U.S. Naval Institute Press book (2004) [ISBN
> 1-59114-061-7].
> It is "based on extracts from English translations of essays written
> at the
> request of British Intelligence by nine German admirals who were
> prisoners of war in British hands in 1945" according to the preface
> (p. vii).
>
> Grand Admiral Donitz (p. 71) writes "... the result of the U-boat
> activity was
> extraordinarily disappointing. The chief reason for this was torpedo
> failures.
> If a torpedo shortage had been evident in the early months of the war,
> it
> was now their ineffectiveness in the Norwegian expedition that became
> disastrously apparent. As a result of being in contact with the enemy
> for
> long periods, the U-boats were forced to remain submerged for a very
> long
> time, causing excess pressure in the boat, which penetrated the depth
> chamber of the torpedo and considerably increased the depth
> setting. . . .
> [snip] The reason for the increasing number of torpedo misses was
> only
> understood by the German navy at a very much later date, when the
> individual technical faults of the torpedo were ascertained by
> systematic
> testing.
>
> Thanks . . . J

An inch of water translates to .48 psi/ft. giving 2/12 of that or

On Thursday, April 12, 2012 1:05:49 AM UTC-4, J wrote:
> This ignorant civilian would like to know why a U-boat, forced to
> remain
> submerged for a long time, would develop excess pressure.
>
> Background: I'm currently reading "Hitler's Admirals" by G.H. Bennett
> and
> R. Bennett, a U.S. Naval Institute Press book (2004) [ISBN
> 1-59114-061-7].
> It is "based on extracts from English translations of essays written
> at the
> request of British Intelligence by nine German admirals who were
> prisoners of war in British hands in 1945" according to the preface
> (p. vii).
>
> Grand Admiral Donitz (p. 71) writes "... the result of the U-boat
> activity was
> extraordinarily disappointing. The chief reason for this was torpedo
> failures.
> If a torpedo shortage had been evident in the early months of the war,
> it
> was now their ineffectiveness in the Norwegian expedition that became
> disastrously apparent. As a result of being in contact with the enemy
> for
> long periods, the U-boats were forced to remain submerged for a very
> long
> time, causing excess pressure in the boat, which penetrated the depth
> chamber of the torpedo and considerably increased the depth
> setting. . . .
> [snip] The reason for the increasing number of torpedo misses was
> only
> understood by the German navy at a very much later date, when the
> individual technical faults of the torpedo were ascertained by
> systematic
> testing.
>
> Thanks . . . J

For a 20 inch hatch with an internal pressure of 2" water gives about 300 lbs required to hold the hatch down. If someone filled that entire hatch they'd have 300 lbs pushing up on them. Interesting.

[peter skelton]

"Vaughn" wrote in message news:jqtoom$gvo$1...@speranza.aioe.org...

On 6/8/2012 4:03 PM, peter skelton wrote:
> http://www.uboatarchive.net/ has a lot of German manuals and
> translations, much more than I've had time to look at
>
> This from one included for kicks:
>
> Remarks: It should be noted, that when pressure inside the boat
> increases, the depth gauge not longer shows the real depth, but a lesser
> value, relative to the pressure difference between water pressure and
> air pressure inside the boat. That's why the depth should be also
> controlled by means of the Papenberg column, periscope or conning tower
> flood valve.

>I don't pretend to remember what type of depth gauges they actually used
in submarines (even though I'm an ex-submariner), but boat pressure
wouldn't necessarily affect the reading of a gauge, depending on the
design of the gauge. Most common bourdon-style gauges have their cases
vented to the atmosphere. In that case, what you say would be correct.

As I was directly quoting a German manual, I'm damn sure I was correct. As
the quote implies, U Boats had both a Bourdon Tube type device and a
capillary guage

>Other gauges have a sealed atmosphere inside the case. Those are not
affected by local atmospheric pressure.

And don't matter to this discussion

>look up the difference between PSIA and PSIG

>A good place to start: http://en.wikipedia.org/wiki/Pressure_measurement

Why? Do you want a list of the errors?

>Vaughn

[Vaughn]

On 6/8/2012 5:29 PM, peter skelton wrote:

> Why? Do you want a list of the errors?

Yes smart ass. Do that please.

Vaughn

[Eugene Griessel]

Op Sat, 09 Jun 2012 09:57:49 +0100, Jeff <je...@jsystems.com> wrote:

>>
>> For a 20 inch hatch with an internal pressure of 2" water gives about 300 lbs required to hold the hatch down.
>
>If someone filled that entire hatch they'd have 300 lbs pushing up on
>them. Interesting.
>

>Not sure where you get those figures from.
>
> 2" of water = 0.072 psi, and a 20" circular hatch is about 1256 sq
>ins. So that equates to about 90lbs

Mmmm. Pi are square. 10 inches by 10 inches by 3.1415926 = 314 sq
inches. You forgot to take the radius and used the diameter. Around
23 lbs by your figures.

Eugene L Griessel

It's hard to make a comeback when you haven't been anywhere.

[Strobe]

On Fri, 08 Jun 2012 18:38:37 +0200, Eugene Griessel <eug...@dynagen.co.za>
wrote:

I'm pretty sure it'd be a test cock, to see if there's pressure on the other
side of the hatch, and whether it's air or water.
They use(d) such a test cock routinely before opening torpedo tube hatches.

--

Terry V.