Shallow water evasion

[the.terrabyte.pirate]

Originally Posted by treblesum81

Hehe, well, this morning I reassessed that situation and moved the same attack W of Belfast and it was a much better situation. Even with that in mind, you can't stay out of shallow water if you want to harbor raid... so perhaps there is a tactic that works for some people? Anyone care to share how you escape destruction when your leaving the harbor after an attack?

On a somewhat related topic, I'm curious if enemies are able to use hydrophones to detect surfaced boats? I was able to sneak up on a convoy yesterday decks awash with a green detection meter and the lead DD none the wiser, but on diving to periscope depth the meter went instantly red and the DD made a hard about to come look for me... I was in the north atlantic in this case and was able to simply dive to 210m and sneak away, but I'm curious if DD's can listen while you're technically surfaced?

Thanks,
Greg

DD's can't use their hydrophones to hear you on the surface. They rely on visual or radar contacts. When you submerge, they use the hydrophones.

If you're closing on a convoy on the surface at ahead full, you won't be heard, so you won't be attacked until you're spotted. If you dive to periscope depth, but don't adjust your speed, you'll be advertising your position on the hydrophones, and you'll attract the escorts like fleas to a dog.

Decks awash is technically surfaced. They won't pick you up on the hydrophones until you're fully submerged.

Until then, I guess your noise tends to blend in with the surface turbulation, or the sounds of the other vessels in the convoy.

[Tessa]

Dealing with DD's in harbors is more like a chess match than an evasion. There are a lot of potential obsticals that you can use to cloak yourself or use to trap the ships above. Be sure though that you've got plenty of air as you could be submerged for a very long time.

You can hide inside the individual ship docks, will make it hard to find you and hard to hit if they do manage. Hide next to a ship or better, a sinking ship (just be careful as they still move once sunk so if you tc you might end up drifting into it) to protect yourself. Escorts don't seem to carpetbomb dc's next to a tanker. Eventually it may give up and go back to it normal patrol and you can move around again. If not, best option in my experience is to sink the thing. Lure him into a position such that he has to come at you directly astern or from the bow (just as long as he can't flank you) and have your weps plot a solution when he's 400m away and fire once its ready (an electric set at 45m) or if using manual be sure to release the eel when he hits 350m to be sure the torpedo has enough time to arm itself.

P.S. Silent speed when your in trouble with little room is always 1 knot and always try to set your rudders to 2-4 degrees in either direction. Constantly turning helps to make you a bit harder to find.

[Catfish]

Hello,
only to put some more oil into the fire
I do not know how SH3 handles this, but a submarine which is at periscope depth can usually not be detected in reality, for the following reasons:

Hydrophones: the surface noise of waves, even when it is almost calm, prevents a detection, if you do not crash a hammer against the hull. Running silent with up to 150 propshaft rpm will not give away your position. Just do not stick the periscope out too long ...

Early sonar/Asdic: the detection cone in front of a destroyer will not find a sub at periscope depth, because even its upper face has a downward angle which will pass below the boat. A boat that is so near as to be hit by the impulses, will 1st most probably be rammed in the next second with or without detection, and 2nd a hitting impuls would not be directly reflected to its source as long as the destroyer moves.

Only possibility is a thermal or density layer below the sub that would reflect the sonar impulse upward again, and then "touch" the boat. Even then the physical situation has to be in a way that those impulses are directly reflected.

Both statements are from a book "Submarine hunt and detection" from the 1960 ies, and even in that time with developped hydrophones and sonar etc. it was virtually impossible to find a sub at PD.

The only "classic" sub game with Diesel/electric boats i know of, that represented that behaviour, was "Wolfpack". If SH3 can be tweaked to represent this i would like to see it. Speaking of oil again lol ...

Greetings,
Catfish

[treblesum81]

Hehe, well, from the sounds of it there are 3 components to staying alive in shallow waters:

1: Luck

2: Finding a good hiding spot

3: Not being stupid enough to go in there in the first place

Sound about right? :p
That being said of course, a lot of good targets sit in harbors and convoys are often easy to work with in the limited inter-island waterways. Oh well, I've been wanting to try looking for some of the bigger seagoing targets since those seem to pose a different kind of challenge altogether in that first you have to find them, then get into position with some good thought, and then manage to get away with nothing but depth to hide in.

I did manage to bag an illustrious carrier last night, it was quite a catch, but then I had to spend the next few hours at 150m trying to evade all 6 of the carrier escorts hunting me down...

Out of curiosity, I know that op depth on a VIIB is stated at 150m and max at 220m but I've seen posts here talking regularly about operating at max depth and some that go much further than that... What is the real crush depth on these, and how bad of an idea is it to get right down on it?

@Catfish
Those are interesting points... though I'm not sure how accurate they are, only because if they were really the case, U-boats would have simply just stayed at PD when trying to evade and never gotten sunk because they could sneak away easily. That being said, there are also a lot of other factors there that might be in play and I think it would be worthwhile to include those modellings if they are accurate... GWX et al have made the game so much more interesting and realistic with their addons, but they've essentially made it a lot harder too. Wouldn't it be nice if adding realism could help out in some little way to counteract that.

Greg

[Catfish]

Hello treblesum81,
the numbers and situations are from the book i mentioned, and i believe them to be exact. Mr. Topp, who had sunk quite some tonnage, and survived the war, also mentioned that strategy. In fact he said he usually never dived to more than 30 meters for exactly that reason.

A boat hearing a destroyer start its attack run could go to full speed undetected, the destroyer is virtually blind during the attack run. If you are at PD the destroyer has to be REAL fast not to be sunk by its own depth charges, being adjusted for exploding at 15 meters.

Bystanding destroyers would as well not hear you because of the attacking destroyers cavitation noises, and no one wanted to ruin his ears hearing exploding charges at the hydrophone. As well in the first years of the war depth charges often exploded at the wrong depth, having similar problems with depth settings as the torpedoes of all nations.

If the enemy exactly knew where you were (spotted your periscope) you would probaly dive deeper to evade the depth charges: One reason is the deeper you are the more the enemy has to calculate sinking speed of the charges against the movements of the sub. And as well a depth charge in say 200 meters does not have the kill radius it would have in shallow waters - water pressure is your friend here.

Even today e.g. a diesel-electric russian "Kilo" sub can only be found by means of exhaust Diesel detection when running at PD charging the batteries, and the Diesel-generated noise.
As soon as it switches to electric propulsion the only possibility for detection is to use submerged sonar buoys, that direct the impulses upward, and are in that case able to detect the sub. Certainly there are other detection strategies today, but not in WW2 anyway.
One of the advisors for SH3, also a real ex-U-boat commander from WW2, said the SH3 vanilla game was already much too hard compared to reality.

Greetings,
Catfish

[Jimbuna]

Good post

[treblesum81]

Agreed, very good post..

I'm interested to know more of the reasoning behind how the game is harder than it was in real life... did he elaborate any on the reasoning behind the statement at all? I know that it couldn't possibly have been as hard as its is in GWX, but the stock game was pretty easy to start with, meaning that he was basically saying that real life U-boating was like Sunday cruising with the chance of losing your life...

Speaking to the GWX team here, I think it would be fair if you all had a look into this data, as it may help to further improve balance and realism within your mod, and in addition, I imagine it would help a lot of people enjoy your addon further. I'll say though that I'm not thinking this would become an easy way to lose DD's as I'm sure there are plenty of other detection strategies that one might fall prey too, but I think that in many cases, GWX seems to model almost exclusively the aspects of U-Boat operations that serve to make life more difficult and not all that many that make it easier. Just a thought.

Greg