to the bottom ?

[DJS4000]

Originally Posted by Aras

Thanks for the help Rconch. Just watched The Enemy Below, that’s where I got the idea

In the movie, the sonar operator of the DD was not able to detect the u boot sit on the bottom, the operator told "Just reflections from the bottom" however shouldn’t he be able to recognize metal from rock or sand ?

that's not how sonar works

[Sailor Steve]

Several submarines reported using that tactic successfully during the war. Most notable was USS S-38, which used it to good effect three different times over a three-day period. This is not to say it would work all the time. We don't know how many tried it and failed.

[Jimbuna]

Originally Posted by DJS4000

that's not how sonar works

It is in SH3

[Marcello]

OTOH, just because you are resting on the bottom it does not mean you are undetectable. I would suspect that a WW2 sonar might have a more difficult time discriminating the submarine from the sea floor and you can pass yourself off for a wreck but that's it. For what is worth I found this reference

Schnorchel U-boat has been the chief concern of surface craft, whose main difficulty has been that of distinguishing between a bottomed U-boat and a wreck. An extensive survey of wrecks in British waters helped considerably in solving this problem.

As I recall the Lusitania wreck was used for ASW target practice and is said to be littered with hedgehog projectiles. At one point one was brought up by divers who had exchanged it for a bottle, needless to say it was quite a shock

that's not how sonar works

Actually different materials do have different reflection characteristics, though how well ww2 vintage sonars could exploit that I would not know.

[Aras]

Originally Posted by Marcello

I would suspect that a WW2 sonar might have a more difficult time discriminating the submarine from the sea floor and you can pass yourself off for a wreck but that's it.

Very good point. I tried this yesterday, I sit on the bottom (65 m) repaired my damage, rig for silent running ,set course to 10, left the sea floor with 1 knots. however a few minutes later the DD which was hovering on the surface ,started to ping again. Got away securely.

The Year is 1940,Scapa Flow. Terrific Weather, can't see further than 600-700 meters. Lots of DD patrolling there I wonder why While heading for the western Cost of England, I Sunk 1 A&B Class with magnetic torpedo

[Grun Teufel]

Originally Posted by Aras

Very good point. I tried this yesterday, I sit on the bottom (65 m) repaired my damage, rig for silent running ,set course to 10, left the sea floor with 1 knots. however a few minutes later the DD which was hovering on the surface ,started to ping again. Got away securely.

The Year is 1940,Scapa Flow. Terrific Weather, can't see further than 600-700 meters. Lots of DD patrolling there I wonder why While heading for the western Cost of England, I Sunk 1 A&B Class with magnetic torpedo

I have "laid flat" against the sea floor before with very positive results. Early in the war, it works like a charm. Just hold still and repair damage only. I once had two DDs try to find me for hours. They kept a "tag team" like system in the area . One would try to ping and hear for me while the other would depth charge where they thought I was. However, the area they chose was a few hundred meters away. While timing myself to the depth charges, I slowly crawled away; stopping when the depth charges stop. The other DD began his attack run dropping more depth charges in the area that they thought I was in, so I moved again because the noise from the depth charges disrupt the sonar and the guy on the hydrophones can't decipher anything but the explosions making your escape possible.
At this point my depth under keel was about 2 meters, sometimes just 1. I think I was between 60 to 70 below the surface. Clear weather too. That is another factor too- weather. If the sea above you is rough, that will make the enemy's search for you even more rough.
I hope this bit of story telling helps you out of a close call or two.
Good Luck and Happy Hunting!

[Aras]

Originally Posted by Grun Teufel

That is another factor too- weather. If the sea above you is rough, that will make the enemy's search for you even more rough.
I hope this bit of story telling helps you out of a close call or two.
Good Luck and Happy Hunting!

I will defiantly keep this in mind. Thx