Diving Depths - U-Boats and FleetBoats

-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.

U-Bones · 04-30-07, 03:35 PM

A hull that is almost twice as thick and tested to go almost twice as deep? Sounds pretty predictable to me

SteamWake · 04-30-07, 03:37 PM

Quote:

Originally Posted by AVGWarhawk

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.

Imagine that american engineers being conservative ?!

Some went past that depth and never returned.

Ducimus · 04-30-07, 04:00 PM

Thickness and grade of steel used on the pressure hull most certainly effected crush depth.

Without having design planes in front of me, im guessing that size of the boat, (larger the boat, the more water it displaces, the greater the pressure per square inch on the hull as a whole? ) and the structural arrangement/placment of the ribs and supportiing skeletal members also would make a difference.

LZ_Baker · 04-30-07, 04:42 PM

The pressure per square inch is the same no matter what the area. Larger area = Larger force = Same PSI. The thickness of the hull matters, but the strength of the material matters even more. Normal steel has a yeild of 32,000 psi. High strength steel is 51,000 psi. HY-80 has a 80,000 psi yield. So 1/2" of HY-80 would be stronger than 1" of normal steel. As stated above, the US hulls were thinner but were made of a stronger material (I would assume, especially late war when Germany was running short of speciallty materials). Also, every engineering design has factors of safety. You rate something for a force when in reality it could take 5 times that force without yielding (example - any type of rigging equipment) 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).

Storabrun · 04-30-07, 08:22 PM

I would assume that the thickness is actually more important than the strength of the material in this case. I'm no expert in submarine design, but if we want to simplify this it's probably more related to bending of a bar than to pulling it apart. 80,000 psi is better than 32,000 of the double thickness when it comes to pulling a rod apart, but not when trying to bend it since strength against bending is proportional to the square of the thickness. The better quality steel would have an edge of 25% for pulling, but the thicker normal steel would be 60% stronger against bending.

LZ_Baker · 04-30-07, 08:39 PM

Quote:

Originally Posted by Storabrun

I would assume that the thickness is actually more important than the strength of the material in this case. I'm no expert in submarine design, but if we want to simplify this it's probably more related to bending of a bar than to pulling it apart. 80,000 psi is better than 32,000 of the double thickness when it comes to pulling a rod apart, but not when trying to bend it since strength against bending is proportional to the square of the thickness. The better quality steel would have an edge of 25% for pulling, but the thicker normal steel would be 60% stronger against bending.

Touche

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.

04-30-07, 04:42 PM	#6
LZ_Baker Engineer Join Date: Mar 2005 Location: Boston Posts: 213 Downloads: 51 Uploads: 0	The pressure per square inch is the same no matter what the area. Larger area = Larger force = Same PSI. The thickness of the hull matters, but the strength of the material matters even more. Normal steel has a yeild of 32,000 psi. High strength steel is 51,000 psi. HY-80 has a 80,000 psi yield. So 1/2" of HY-80 would be stronger than 1" of normal steel. As stated above, the US hulls were thinner but were made of a stronger material (I would assume, especially late war when Germany was running short of speciallty materials). Also, every engineering design has factors of safety. You rate something for a force when in reality it could take 5 times that force without yielding (example - any type of rigging equipment) 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). __________________

04-30-07, 03:22 PM	#1
-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-

04-30-07, 03:35 PM	#3
U-Bones Grey Wolf Join Date: Mar 2005 Location: Treading Water Posts: 847 Downloads: 56 Uploads: 0	A hull that is almost twice as thick and tested to go almost twice as deep? Sounds pretty predictable to me

04-30-07, 04:00 PM	#5
Ducimus Rear Admiral Join Date: May 2005 Posts: 12,987 Downloads: 67 Uploads: 2	Thickness and grade of steel used on the pressure hull most certainly effected crush depth. Without having design planes in front of me, im guessing that size of the boat, (larger the boat, the more water it displaces, the greater the pressure per square inch on the hull as a whole? ) and the structural arrangement/placment of the ribs and supportiing skeletal members also would make a difference.

04-30-07, 08:22 PM	#7
Storabrun Loader Join Date: Apr 2006 Posts: 83 Downloads: 0 Uploads: 0	I would assume that the thickness is actually more important than the strength of the material in this case. I'm no expert in submarine design, but if we want to simplify this it's probably more related to bending of a bar than to pulling it apart. 80,000 psi is better than 32,000 of the double thickness when it comes to pulling a rod apart, but not when trying to bend it since strength against bending is proportional to the square of the thickness. The better quality steel would have an edge of 25% for pulling, but the thicker normal steel would be 60% stronger against bending.