Seafloor's ASDIC protection

Matyas · 02-21-08, 09:15 AM

I'm currently in a dilemma. I have received a radio report about a convoy travelling along the eastern shores of Britain where the sea is quite shallow (30 meters at most) and I don't know whether it is worth the risk of engagment: if an escort picks me in such shallow water I'm dead meat as I can't escape their ASDIC by diving deep. (Also the low water pressure expands the lethal radius of DCs in theory, so they don't even have to be too precise to kill me.)

I faintly remember a story told by a German U-boat commander (maybe in Discovery channel): he said that their tactics in shallow water was coming to a full stop and lying down onto the seabed. That way they were undetectable to both hydrophones and ASDIC as they didn't make any noise and the sonic (echo) waves bouncing off the seabed created a lot of "noise" that hid them.

Does anyone have any idea about whether this phenomenon (i.e. the seafloor hides U-boat from ASDIC) is modeled in SH3? Knowing this would greatly help me doing my "risk analysis" before the attack.

BTW a second question: is the lethal (or effective) radius of DCs affected by depth (water pressure) in SH3? :hmm:

Sailor Steve · 02-21-08, 11:15 AM

Yes, the Germans used it, and to good effect. The Americans did it also, most notably S-36 at Lingayen Gulf. The added advantage is that the sand absorbs the blast of the depth charges, so they're not only dropping blind, but they have to get very lucky to hurt you.

The bad news is that no, none of this is reflected in the game, and it's part of the main code, so no one can change it.

Boris · 02-21-08, 11:23 AM

Yeah, I've been bombed out of existence lying motionless on the seabed several times.

bigboywooly · 02-21-08, 12:19 PM

Not too sure about being totally undetectable sat on the sea bed
There are more than a couple of accounts of warships dropping DCs on what they thought were sub targets only to find out later were wrecks

Gezur(Arbeit) · 02-21-08, 12:41 PM

shipwrecks are bigger and higher than uboats

Jimbuna · 02-21-08, 01:08 PM

Quote:

Originally Posted by Gezur(Arbeit)

shipwrecks are bigger and higher than uboats

That may be true, but in-game your afforded no protection. The asdic (and sonar) can 'see' through small land masses.

Sailor Steve · 02-21-08, 03:17 PM

Quote:

Originally Posted by bigboywooly

Not too sure about being totally undetectable sat on the sea bed
There are more than a couple of accounts of warships dropping DCs on what they thought were sub targets only to find out later were wrecks

We also have no accounts from submariners for whom it didn't work; and with good reason.

I've related before the story of my aerodynamicist friend talking about the famous dive rate of the P-47 thunderbolt. Every time someone says "Yeah, they always got away from the Germans by out-diving them!", my friend replies "Well, except for the ones who didn't; and they ain't talking!"

irish1958 · 02-21-08, 08:18 PM

Sitting on the sea floor has been the death of several of my unfortunate boats. I wouldn't recommend it.

Jimbuna · 02-22-08, 10:31 AM

Quote:

Originally Posted by irish1958

Sitting on the sea floor has been the death of several of my unfortunate boats. I wouldn't recommend it.

All your actually doing is saving the game the bother of putting you there....forever

STEED · 02-22-08, 01:56 PM

Sitting on the sea floor only makes there job more easy.

Gezur(Arbeit) · 02-22-08, 02:31 PM

my post on the shipwrecks was for reallife...not for Sh3, because i dont think escorts in sh3 will depthcharge shipwrecks.

Jimbuna · 02-22-08, 03:15 PM

Quote:

Originally Posted by Gezur(Arbeit)

my post on the shipwrecks was for reallife...not for Sh3, because i dont think escorts in sh3 will depthcharge shipwrecks.

That's because they're no longer rendered shortly after they sink.....unless the water is quite shallow

johnno74 · 02-22-08, 11:56 PM

In real life sitting on the seabed doesn't make you invisible to sonar/ASDIC. Sonar works on the principle that when a sound wave hits something with a different density, part of the sound is reflected back. About the biggest density change possible is when the sound wave travels through a sub's pressure hull, then reaches the air trapped within.

So if you are sitting on the bottom in real life, yes you will be camoflagued to a certain degree because the sonar "pings" reflect off the denser sea floor, but a trained sonar operator can definitely pick up the much stronger reflection off your submarine. Now I don't know a hell of a lot about sonar besides the scientific principles, so I can't tell you just how easy it is to pick up a sub on the seafloor with WWII equipment, but it is certainly possible. With modern equipment it is trivial. Even a basic fish-finder would show up a submarine on the bottom as plain as daylight.

In WWII U-boats sitting on the sea-floor were NOT invisible.

Der Teddy Bar · 02-23-08, 06:02 AM

There is the slight issue of oil slicks.

I have read quit a few instances where a u-boat was detected by aircraft because of a trailing oil slick. Most of these instances where of a moving u-boat in deep water well into the Atlantic ocean.

It is my understanding that the sea bed was a good hiding place when the enemy was not aware of your presence but not so affective when you were being hunted.

02-21-08, 09:15 AM	#1
Matyas Seaman Join Date: Jan 2007 Location: Budapest Posts: 42 Downloads: 9 Uploads: 0	Seafloor's ASDIC protection I'm currently in a dilemma. I have received a radio report about a convoy travelling along the eastern shores of Britain where the sea is quite shallow (30 meters at most) and I don't know whether it is worth the risk of engagment: if an escort picks me in such shallow water I'm dead meat as I can't escape their ASDIC by diving deep. (Also the low water pressure expands the lethal radius of DCs in theory, so they don't even have to be too precise to kill me.) I faintly remember a story told by a German U-boat commander (maybe in Discovery channel): he said that their tactics in shallow water was coming to a full stop and lying down onto the seabed. That way they were undetectable to both hydrophones and ASDIC as they didn't make any noise and the sonic (echo) waves bouncing off the seabed created a lot of "noise" that hid them. Does anyone have any idea about whether this phenomenon (i.e. the seafloor hides U-boat from ASDIC) is modeled in SH3? Knowing this would greatly help me doing my "risk analysis" before the attack. BTW a second question: is the lethal (or effective) radius of DCs affected by depth (water pressure) in SH3? :hmm: Last edited by Matyas; 02-21-08 at 09:53 AM.

02-21-08, 11:15 AM	#2
Sailor Steve Eternal Patrol Join Date: Nov 2002 Location: High in the mountains of Utah Posts: 50,369 Downloads: 745 Uploads: 249	Yes, the Germans used it, and to good effect. The Americans did it also, most notably S-36 at Lingayen Gulf. The added advantage is that the sand absorbs the blast of the depth charges, so they're not only dropping blind, but they have to get very lucky to hurt you. The bad news is that no, none of this is reflected in the game, and it's part of the main code, so no one can change it. __________________ “Never do anything you can't take back.” —Rocky Russo

02-21-08, 12:19 PM	#4
bigboywooly Rear Admiral Join Date: Apr 2006 Location: Swindon, England Posts: 10,151 Downloads: 35 Uploads: 0	Not too sure about being totally undetectable sat on the sea bed There are more than a couple of accounts of warships dropping DCs on what they thought were sub targets only to find out later were wrecks __________________ My mediafire page http://www.mediafire.com/?11eoq19bq9r41

02-21-08, 08:18 PM	#8
irish1958 Ocean Warrior Join Date: Apr 2005 Location: Carmel, Indiana Posts: 3,250 Downloads: 320 Uploads: 11	Sitting on the sea floor has been the death of several of my unfortunate boats. I wouldn't recommend it. __________________ Irish1958

02-22-08, 01:56 PM	#10
STEED Lucky Jack Join Date: Jan 2006 Location: Down Town UK Posts: 27,695 Downloads: 89 Uploads: 48	Sitting on the sea floor only makes there job more easy. __________________ Dr Who rest in peace 1963-2017. To borrow Davros saying...I NAME YOU CHIBNALL THE DESTROYER OF DR WHO YOU KILLED IT!

02-21-08, 11:23 AM	#3
Boris Sea Lord Join Date: Jun 2005 Location: Hamburg, Germany Posts: 1,691 Downloads: 41 Uploads: 0	Yeah, I've been bombed out of existence lying motionless on the seabed several times.

02-21-08, 12:41 PM	#5
Gezur(Arbeit) Soundman Join Date: Jan 2008 Posts: 149 Downloads: 0 Uploads: 0	shipwrecks are bigger and higher than uboats

02-22-08, 02:31 PM	#11
Gezur(Arbeit) Soundman Join Date: Jan 2008 Posts: 149 Downloads: 0 Uploads: 0	my post on the shipwrecks was for reallife...not for Sh3, because i dont think escorts in sh3 will depthcharge shipwrecks.

02-22-08, 11:56 PM	#13
johnno74 Planesman Join Date: Nov 2006 Location: Melbourne, Australia Posts: 197 Downloads: 5 Uploads: 0	In real life sitting on the seabed doesn't make you invisible to sonar/ASDIC. Sonar works on the principle that when a sound wave hits something with a different density, part of the sound is reflected back. About the biggest density change possible is when the sound wave travels through a sub's pressure hull, then reaches the air trapped within. So if you are sitting on the bottom in real life, yes you will be camoflagued to a certain degree because the sonar "pings" reflect off the denser sea floor, but a trained sonar operator can definitely pick up the much stronger reflection off your submarine. Now I don't know a hell of a lot about sonar besides the scientific principles, so I can't tell you just how easy it is to pick up a sub on the seafloor with WWII equipment, but it is certainly possible. With modern equipment it is trivial. Even a basic fish-finder would show up a submarine on the bottom as plain as daylight. In WWII U-boats sitting on the sea-floor were NOT invisible. __________________ When you pull the pin from Mr. Grenade, he is no longer your friend.

02-23-08, 06:02 AM	#14
Der Teddy Bar Blade Master Join Date: Jan 2002 Posts: 1,388 Downloads: 0 Uploads: 0	There is the slight issue of oil slicks. I have read quit a few instances where a u-boat was detected by aircraft because of a trailing oil slick. Most of these instances where of a moving u-boat in deep water well into the Atlantic ocean. It is my understanding that the sea bed was a good hiding place when the enemy was not aware of your presence but not so affective when you were being hunted.