Diving Depths - U-Boats and FleetBoats - Page 2

Crosseye76 · 05-01-07, 02:54 AM

And don't forget guys, your not just talking about the pressure hull here.

A Submarine is a ship, not a an unbroken tube of steel. A lot of these dive limits were not based only on the yield strength of the pressure hull.

They were also based on all the many other systems that had to stand up to sea pressure. Shaft seals, Periscope and other mast glands, depth sensing inputs, Etc.

I can't dig up the source now, but I seem to remember a comment about the U.S. pumps. Based on a WW 1 design, they could only overcome sea pressure down to a certain depth, so they could not pump overboard below 300 - 400 feet or so.

Every time we went below a certain depth on the 643 boat, there was a "Deep Submergence" bill. This closed some un-needed sea pressure exposed systems (The Depth input line to the Hovering system for instance) and gave instructions on systems to monitor and keep an eye on.

We never worried about the Pressure hull giving up the ghost, it was FAR more likely that a problem would arise from all the various holes in that hull than from the hull itself.

Sailor Steve · 05-01-07, 10:52 AM

Quote:

Originally Posted by NEON DEON

What U-boat had a 25 mm hull?
VII C: 18.5 mmVII/41 21 mm

The quote was from Padfields War Beneath The Sea. I assume he was generalizing. Still, it's a lot more than 1/2".

Bilge_Rat · 05-01-07, 11:01 AM

Quote:

Originally Posted by LZ_Baker

The US subs were rated for 400' but one managed to go down to 1000' and survive (don't remember what boat, its posted around here somewhere).

That was the USS Chopper, a Balao class, but the hull was permanently damaged, so the safe operating depth would probably be somewhere between 400 and 1,000.

In Silent Victory, I also read about an earlier sub, P class I think, which accidently dove down to 600 feet while under attack in the summer of 1942. The hull was damaged, but in the text, its not clear if its from the dive or the depth charging.

So I would think a Balao class could go down to 600 feet without breaking a sweat and if it was in perfect condition, could probably edge down to 800 feet without too much risk.

AhhhFresh · 05-01-07, 11:11 AM

Quote:

Originally Posted by Chock

Ever since WW1, Germany was noted for being well in advance of other countries in techniques for metal fabrication (notably welding). This is remarked upon in many allied documents with regard to captured WW1 German equipment, so maybe this is also a factor.

I think this may be a big part of it... almost all of the US ships pre-Pearl were riveted instead of welded. The demand for fast ship construction changed that pretty quickly, but I don't imagine they were experts from the start. The S-boats had completely riveted hull constructions, and it wasn't until the Gatos that they started using fully welded hulls.

I wouldn't be surprised to find that the Germans had been using fully welded hulls since WWI in their U-boats.

EDIT: Whoops! Missed the important part of the quote!

7Enigma · 05-01-07, 11:22 AM

Very intesting thread everyone. Keep up the chatter!

jetthelooter · 05-01-07, 11:45 AM

i faintly remember reading an article on the differences between US submarine construction theory and practice and the german same. if i am remembering correctly the germans used a much smaller determination of crush depth than the amercians did meaning that their doctrine called for much deeper diving before reaching crush depth. this allowed them a smaller margin for error when approaching the rated crush depth.

the american estimations were much more conservative making for a much shallower listed crush drepth as the concern was for safety more than anything. in reality both the german and american subs realistically had very similar depths they could dive without damage or implosion. it seemed to me from that article it was more a matter of naval doctrine than actual depth at which the sub would implode. if i remember right the american method for estimating max dive depth was about half of crush depth which is what is usually listed as that sub types max depth.

from what i have read about american sub skippers they would exceed the listed max safe depth by up to half and tend not to record said depth in the log.

so if you consider that the german and american subs had similar dive capabilities and depths. one navy was just doctrinely more conservative than the other.

05-01-07, 02:54 AM	#16
Crosseye76 Lieutenant Join Date: Feb 2007 Location: Las Vegas Posts: 258 Downloads: 0 Uploads: 0	And don't forget guys, your not just talking about the pressure hull here. A Submarine is a ship, not a an unbroken tube of steel. A lot of these dive limits were not based only on the yield strength of the pressure hull. They were also based on all the many other systems that had to stand up to sea pressure. Shaft seals, Periscope and other mast glands, depth sensing inputs, Etc. I can't dig up the source now, but I seem to remember a comment about the U.S. pumps. Based on a WW 1 design, they could only overcome sea pressure down to a certain depth, so they could not pump overboard below 300 - 400 feet or so. Every time we went below a certain depth on the 643 boat, there was a "Deep Submergence" bill. This closed some un-needed sea pressure exposed systems (The Depth input line to the Hovering system for instance) and gave instructions on systems to monitor and keep an eye on. We never worried about the Pressure hull giving up the ghost, it was FAR more likely that a problem would arise from all the various holes in that hull than from the hull itself. __________________ There are only two kinds of ships. Submarines and Targets.

05-01-07, 11:22 AM	#20
7Enigma Helmsman Join Date: Apr 2007 Posts: 103 Downloads: 0 Uploads: 0	Very intesting thread everyone. Keep up the chatter!

05-01-07, 11:45 AM	#21
jetthelooter Watch Join Date: May 2007 Posts: 24 Downloads: 0 Uploads: 0	i faintly remember reading an article on the differences between US submarine construction theory and practice and the german same. if i am remembering correctly the germans used a much smaller determination of crush depth than the amercians did meaning that their doctrine called for much deeper diving before reaching crush depth. this allowed them a smaller margin for error when approaching the rated crush depth. the american estimations were much more conservative making for a much shallower listed crush drepth as the concern was for safety more than anything. in reality both the german and american subs realistically had very similar depths they could dive without damage or implosion. it seemed to me from that article it was more a matter of naval doctrine than actual depth at which the sub would implode. if i remember right the american method for estimating max dive depth was about half of crush depth which is what is usually listed as that sub types max depth. from what i have read about american sub skippers they would exceed the listed max safe depth by up to half and tend not to record said depth in the log. so if you consider that the german and american subs had similar dive capabilities and depths. one navy was just doctrinely more conservative than the other.