Diving Depths - U-Boats and FleetBoats

csargemg · 04-30-07, 10:19 AM

Is there a reported reason why the U-Boat diving capabilities were so much greater than those of the American submarines, particularly in consideration of diving ability vs. boat length? The American subs can barely dive deeper than their own lengths, while Type VIIs are reported (as I'm sure you know by Erich Topp) to have gone down as far as 250 meters.

Is the cruising range and the massive amounts of fuel storage needed on the fleet boats a factor, or what?

Sailor Steve · 04-30-07, 10:24 AM

When the British captured their first type VII, they were astonished to find that the Germans were building pressure hulls out of 25mm steel, which is not quite 1 inch thick; as opposed to their own, which was only 1/2" (12.7mm). the Americans were using 5/8" (14mm) until the Balao class, which not only had 7/8" thickness, but was also made from STS (Special Tensile Steel), otherwise known as armor plate.

That said, some US boats did indeed reach depths they were told not to go to, with little or no problem.

csargemg · 04-30-07, 10:29 AM

Even still, the test depth of the Type VII was 230 meters, and the test depth of the Balao was 122 meters. Perhaps the small size of the Type VII pressure hull magnifies its greater thickness?

madmax · 04-30-07, 03:07 PM

There is an element of design involved.... The weakest link etc and shape of the pressure hull.

The Germans were some years ahead of everyone in both submarine /rocket and airplane design. Probably a few germans lying around in both East and West sub development programs.

-Pv- · 04-30-07, 03:22 PM

The problem of how deep to go is relative though. In the Pacific the Japanese had bad intel on US sub diving depth and habitually se their DC too shallow (not having good sonar made this worse early in the war) so really all that in necessary is that you can go deep enough to play the game successfully and this is certainly the case (in an unmodded game.)
-Pv-

AVGWarhawk · 04-30-07, 03:29 PM

Quote:

Balao class submarines were an improved version of the previous Gato class. They were designed to dive to a depth of 400 feet as opposed to the 300 feet for Gato class boats

Apparently this is all they were designed to do, 400 feet. Many went past this mark so I guess the designer were keeping it conservative.

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.

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.

04-30-07, 10:19 AM	#1
csargemg Watch Join Date: Jan 2007 Posts: 17 Downloads: 46 Uploads: 0	Diving Depths - U-Boats and FleetBoats Is there a reported reason why the U-Boat diving capabilities were so much greater than those of the American submarines, particularly in consideration of diving ability vs. boat length? The American subs can barely dive deeper than their own lengths, while Type VIIs are reported (as I'm sure you know by Erich Topp) to have gone down as far as 250 meters. Is the cruising range and the massive amounts of fuel storage needed on the fleet boats a factor, or what?

04-30-07, 10:24 AM	#2
Sailor Steve Eternal Patrol Join Date: Nov 2002 Location: High in the mountains of Utah Posts: 50,369 Downloads: 745 Uploads: 249	When the British captured their first type VII, they were astonished to find that the Germans were building pressure hulls out of 25mm steel, which is not quite 1 inch thick; as opposed to their own, which was only 1/2" (12.7mm). the Americans were using 5/8" (14mm) until the Balao class, which not only had 7/8" thickness, but was also made from STS (Special Tensile Steel), otherwise known as armor plate. That said, some US boats did indeed reach depths they were told not to go to, with little or no problem. __________________ “Never do anything you can't take back.” —Rocky Russo

04-30-07, 03:07 PM	#4
madmax Swabbie Join Date: Aug 2005 Posts: 5 Downloads: 3 Uploads: 0	Dive Depths There is an element of design involved.... The weakest link etc and shape of the pressure hull. The Germans were some years ahead of everyone in both submarine /rocket and airplane design. Probably a few germans lying around in both East and West sub development programs.

05-01-07, 02:54 AM	#7
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.

04-30-07, 10:29 AM	#3
csargemg Watch Join Date: Jan 2007 Posts: 17 Downloads: 46 Uploads: 0	Even still, the test depth of the Type VII was 230 meters, and the test depth of the Balao was 122 meters. Perhaps the small size of the Type VII pressure hull magnifies its greater thickness?

04-30-07, 03:22 PM	#5
-Pv- The Old Man Join Date: Apr 2006 Posts: 1,434 Downloads: 5 Uploads: 0	The problem of how deep to go is relative though. In the Pacific the Japanese had bad intel on US sub diving depth and habitually se their DC too shallow (not having good sonar made this worse early in the war) so really all that in necessary is that you can go deep enough to play the game successfully and this is certainly the case (in an unmodded game.) -Pv-

05-01-07, 11:45 AM	#8
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.