Could you sit on the bottom and hide in real life?

[maillemaker]

In the game, if you sit on the bottom they will depth charge you until you die.

But in real life, would they be able to distinguish your sub from the sea floor, if all were quiet inside your sub?

Steve

[KL-alfman]

ASDIC would have found your boat, even if there are no noise-emissions, I suppose.

[[SJ]nailz]

ASDIC would have found your boat, even if there are no noise-emissions, I suppose.


But wouldn't it have found the seabed too, like the depth under keel ping??

I suppose a skilled ASDIC operator would be able to tell the difference though, but through constant DC's???

[Dissaray]

A well trained ASW crew might be able to find a uboat sitting on the bottom with the ASDIC. Though it would be much more dificult to do so as the sea bed would return an eco. What would determine if they can find you or not is if they could determine the diferance between the sound reflecting off the sea floor and the sound reflecting off the boat. It would still be difficult I think.

[Matador.es]

This is some i have wounderd to. ASDIC detects distances. Since the distance between a submarine on the bottom and his "background" (the bottom) is close to none. Since it is not a metal detecting system you will not see any differance. I would also think that being on the bottom will make you unvisible for active sonar.

Will check on it within a few days 2 make sure.

Matador

[maillemaker]

The only thing I would guess is perhaps the metal of the submarine is a better reflector than the ocean floor, and so even though you would see no depth change between the sub and the ocean floor, you might find a spot where you get a stronger return. I don't know how well WWII-era sonar worked in that regard, though.

If all it did was measure distance to object, I would think a sub would tend to blend in with the bottom.

But then again, from some pictures I've seen of dry-docked subs, the things must have been at least 30 feet tall from keel to bridge, maybe more.

On a flat seabed, maybe that would show up?

[Snestorm]

Without any hint of your being there . . .,
they should NOT be able to detect you.

If you're realy interested in the topic, I'd suggest reading up on english boats.
They tended to "bottom" their boats comparitively more often than other navies because, they practiced more Daylight Submerged Attacks along coastal waterways.
(U-boats and ore carriers being high on the target priority list).

The germans tended to avoid the practice, because of the possibility of damaging the boat.
(Especialy rudders and screws).

[Sailor Steve]

In December 1941 USS S-38 grounded herself three times in one patrol!

Not only were the destroyers unable to locate her against the bottom, but the blast from the depth charges that were dropped tended to be absorbed by the sandy bottom.
http://en.wikipedia.org/wiki/USS_S-38_(SS-143)

It didn't happen often, but yes, there should be a reasonable chance for survival in those conditions.

[Panser]

I've recently finished reading "Operation Drumbeat" by Michael Gannon.

It would seem that Reinhard Hardegen in U-123 (a type IX) rested on the bottom several times in his drumbeat patrols while patrolling close inshore.

In particular his first patrol in US waters - he took a cruise into New York harbour one night, having rested on the bottom of the Hudson river during daylight hours both on his way in and out to avoid detection and passing shipping because the water was so shallow.

[Snestorm]

Tryed to edit my spelling, and pressed the wrong button. disregard.

[Snestorm]

I've recently finished reading "Operation Drumbeat" by Michael Gannon.

It would seem that Reinhard Hardegen in U-123 (a type IX) rested on the bottom several times in his drumbeat patrols while patrolling close inshore.

In particular his first patrol in US waters - he took a cruise into New York harbour one night, having rested on the bottom of the Hudson river during daylight hours both on his way in and out to avoid detection and passing shipping because the water was so shallow.

He, nor any other u-boat ever entered New York Harbor.
The Hudson River?!? Sorry. No way.
Ever heard of Hell's Gate?

[Matador.es]

Euhm, last night i did some thinking while sleeping, and think i have to come back on my statement before.

What i said was the depth difference between a U-Boat and the bottom would be 2 small to notice when its on the bottom. Assuming the ASDIC would detect detp differences. But i start to wonder if that is correct.

Could it not be that the ASDIC detects "180 degree" reflections?

Meaning; a asdic beam send out on 45grad down agnle will bounce with a 90grad on the beam and 45 grad on the bottom back up forward... assuming the bottom is horizontal.

Well now we have a U-Boat on the bottom, which with all it curves and expecially half round shape (side view) will always have a spot where the sound beam will be bounced back strait to where it came from?

To find out the reality one needs to know which of 2 is true, or just ask somebody who really knows....

Interesting mettar though :)

[Dissaray]

If sound waves in the water act like lazers do in the air you would be correct. I am not sure that is how things work. But with the difuse properties of sound as contrasted with the concentrated nature of a lazer I think it is somewhat diferant. While the sound will leve any object it reflects off of at a simular angle it will not continue on that angle as it travles thru the water beacouse the sound is going to spred thru the water particles much like standard light waves do. In the end I guess the best analog would be shining a flashlight into a mirror, while the spred of the light will be simular to that of the angle of entry onto the mirror the farther it traveles from the mirror the greater the deviation from that initial angel will be.

That said I am kind of drunk just now so taking my word on the working physicis of sound and sonar might not be the best idea.

[JamesT73J]

He, nor any other u-boat ever entered New York Harbor.
The Hudson River?!? Sorry. No way.
Ever heard of Hell's Gate?

He had tourist maps of NYC. It's entirely possible he ventured into the mouth of the Hudson. They did just about everything else.

[Panser]

He, nor any other u-boat ever entered New York Harbor.
The Hudson River?!? Sorry. No way.
Ever heard of Hell's Gate?

Apologies about the Hudson river, that was an error in my geography, but he certainly entered the bay of New York Harbour. There is specific mention of him almost running aground in the Ambrose Channel... Given that Hardegen was known for his aggressive and daring behaviour - he's the man that gave the people of Jacksonville Beach, Florida, a grandstand view of the SS Gulfamerica tanker being torpedoed and finished with the deck gun just offshore - it seems quite feasible that he did it.

The Eastern Sea Frontier had next to no defences at the start of Paukenschlag - the entire east coast of the US was literally wide open because the few destroyers and patrol craft that were available were sat idly in harbour doing nothing despite countless warnings from British Enigma and Direction-Finding intercepts. Hardegan's war diary and the ships he sank in the the lower bay before and after his little trip speak for themselves.

Reading the book would be a good start because it is very well cited and referenced; 36 pages of references and 5 pages of "Select Bibliography" would suggest the author did his homework.

[Matador.es]

he's the man that gave the people of Jacksonville Beach, Florida, a grandstand view of the SS Gulfamerica tanker being torpedoed and finished with the deck gun just offshore

Correct, there is a documentary (i have on my pc) from History Channal named
"Silent Service" episode "U-Boot" what reports about it. It used to be on some news.servers.

But lets try to stick to the subject....

[Sailor Steve]

Well now we have a U-Boat on the bottom, which with all it curves and expecially half round shape (side view) will always have a spot where the sound beam will be bounced back strait to where it came from?
In theory, yes, there should be at least one reflection directly back to the pinging destroyer. But that is also true of wrecks, rocks, whales, large shools of fish and undulations in the bottom itself.

All I know for sure is that some submarines did it and got away with it. How many did it and got caught anyway we have no way of knowing.

And then there's the problem of very clear days when a submarine sitting on the bottome might be seen by a patrol plane or blimp.:dead:

[maillemaker]

And then there's the problem of very clear days when a submarine sitting on the bottome might be seen by a patrol plane or blimp.

I think it would be funny if someone parked their sub on the bottom to hide, and they were, in fact, plainly visible from the surface because of clear water, and then the "bad guys" rowed out over them with a rowboat and some chain and "lassoed" themselves a submarine. :)

I could just envision the guys inside their sub, doing whatever, and then feeling a giant "tug...tug...tug" motion and the floor start moving and they hear the sound of being dragged along the sand. :)

"Hayyyyyyy...what's going on here?!?!"

[Matador.es]

And then there's the problem of very clear days when a submarine sitting on the bottome might be seen by a patrol plane or blimp.:dead:

How could that be? At 100m? The mud blurring the water?

[Sailor Steve]

How could that be? At 100m? The mud blurring the water?
We're talking about shallow water. Or were we? I've seen the bottom from the signal bridge of a destroyer, when it was 100' (30 meters) deep or more, but that was the Pacific.

I was thinking east coast USA, and not that deep.

[JamesT73J]

I think - to an experienced operator - a sandy or soft seabed will give a distinctly different echo return compared to a large, metal object.

[Sailor Steve]

Thinking is fine, but several boats did it and sometimes it even worked.

[BillCar]

Thinking is fine, but several boats did it and sometimes it even worked.

This is very true.

For one specific case: HMCS Haida filed an after-action report in July of 1944 in which she (accompanied by HMS Eskimo) sank U-971. They reported losing contact for a while and not being able to get a discernable reading after their second DC run. Haida Captain Harry DeWolfe notes in his report that "it is believed submarine went to the bottom at this time and remained stopped."

U-971 wound up surfacing and eating some of Haida's 4.7" rounds through her conning tower before the crew abandoned ship. But lying on the bottom of the channel for a bit did indeed cause Haida and Eskimo to lose contact.

[Jimbuna]

A small extract from an account of the sinking of U-340:


The U-Boat remained lying on the bottom for about five hours after submerging, and at the end of this time, the supply of air was reduced to a minimum.


http://www.uboatarchive.net/U-340INT.htm

[maillemaker]

It just don't work in SHIII worth a damn. :)

[Coyote88]

Homer Hickam's Torpedo Junction (http://www.librarything.com/work/322520) describes several instances where destroyers found -and, to their embarrassment, attacked - ships that had already been sunk. So sonar could pick up targets on the bottom, but keep in mind that A) sunken ships are much larger than submarines, and B) the water off the Carolina coast is quite shallow for submarine operations.