Not Diving Deep To Escape Escorts

[Simdude]

How often do other subsimmers dive deep? I've only got as far as Aug 40 (i've only been running SH3 for like 3 months or so), but it's been my experience so far that escorts don't seem to be able to detect me at periscope depth, as long as i'm silent running and at slow speed. For example, last night i single torpedoed a small merchant, and then quickly surfaced to finish him off with a half dozen cannon shots...all the while there was an enemy warship about 10-8 km away, at full steam in my direction. I quickly got back to periscope depth, silent running, ahead slow...the warship got within a kilometer of me but he just circled around my old position and i slowly got farther and farther away until he gave up after several minutes and continued on his original course...i never went any deeper than periscope depth. Same thing with a convoy i attacked the other night with at least 3 escorts, they just seemed to circle around the perimeter of the convoy with an occasional ping (guessing where the torpedoes were fired from maybe?), but they didn't even get close to my position and had no clue where i was...again, all at periscope depth. Is sonar not as effective for shallow boats (like airplanes flying low to avoid radar detection)?..because it seems to be working quite well for me so far.

[Haukka81]

Its just bad sonar in early years, Allies will get better sonars later in war

What mod you use ? GwX ?

[Rambler241]

Simdude enquired:

How often do other subsimmers dive deep?

As infrequently as possible - depends entirely on the circumstances. Once you've been detected, it makes sense to escape by going deep and quiet. Incidentally, your tactic of "silent running" and ahead slow is quite likely to lead to detection by determined & experienced escorts. Around 2 knots is much better, but will still not guarantee your boat won't be heard. If a warship gets a sonar echo, going deep and quiet is usually the only option, though there's little to lose by speeding up to get deeper as quickly as possible, and changing course, before going quiet and slow.

You could have saved yourself a torpedo on that small merchant - in my current mission on the way to my patrol grid, I've sunk three SMs in 36 hours, all with the deck gun, four shots each. Two shots to the waterline is usually enough to bring 'em to a halt, on their beam ends, and two more on the waterline on the exposed hull bottom on the other side. When possible, I sink all lone merchants with the gun, except large tankers and C2 cargoes, all of which take a lot of ammo to sink.

In my experience, SMs take between 2 (very lucky that time!) and 6 shots to sink, CMs between 3 and 6, C3s between 5 and 10, including a couple of AP shells, small tankers a few more than C3s.

[MantiBrutalis]

It is a ballsy thing to do, but it is doable early in the war.

The thing is - if you dive deep, the enemy can detect you while you're gaining depth, but you're usually safe if you began your dive early enough. Not diving at all can keep you safe - until the destroyer comes closer by sheer luck. And when you finally get detected at some 300-ish meters while at periscope depth... you are in a sea of trouble.

So I do stay shallow occasionally. But it is hiding in plain sight - get detected and suddenly you're not hiding, you're just in plain sight.

[Simdude]

"your tactic of silent running and ahead slow is quite likely to lead to detection by determined & experienced escorts. Around 2 knots is much better" - but 'ahead slow' IS 2 knots, sir?!

"Two shots to the waterline is usually enough to bring 'em to a halt, on their beam ends, and two more on the waterline on the exposed hull bottom on the other side" - there was no time to maneuver around the merchant and cherry pick deck gun shots, there was a warship close by and inbound fast...i was hoping the torpedo would sink him on impact, so i could quickly run away, but after about a minute of waiting (he was still floating and maneuvering) i decided to quickly surface and guarantee the kill before the cavalry arrived.

[Zosimus]

Well, I go as deep as possible as often as possible. I've been as deep as 264 meters (though that was an accident). I try to keep it right around 259 m when hiding. If it's windy or stormy above, I usually don't have to go that deep. Sonar doesn't work well when there's a lot of commotion at the surface.

[UKönig]

Sonar doesn't work well near the surface in bad weather and stormy seas, and the motion of the ocean is what's known as "surface clutter". In aircraft terms it would be like listening for birdsong in the exhaust trails of a jet plane. Maybe, but unlikely.
In the early war I will go as deep as possible but on average, not more than 285m. In a type 7, I prefer to keep it around 220m. That's because the early depth charges did not go deeper than 152 m, or 498 feet. So as long as you have a comfortable margin over your boat, the charges cannot get you. Go ahead, make as much noise as you like, eventually they will run out. The only problem then is how long will it take for the escorts to go away, vs how long will your air supply or battery power will last.
By the time Jan 1942 rolls around diving very deep offers little protection against the muchly improved asdic and hydrophones of the allies. They also fixed the limitations of the depth charge. There, only your experience will save you. And once they start "pinging" you with active sonar, well, being quiet is out of the question. The return ping is caused by your submarine hull and there is no way, out side of the albericht coating, to conceal it. Once they've found you, they've found you. Again, survival comes down to your own experience and skill.

[Zosimus]

To a certain extent I agree with you. If the sea above is placid, then no depth will save you from ASDIC. However, if there is at least some wind (perhaps 4 m/s) then depth will save you. Run silent; run deep.

[UKönig]

It's true what you say, being quiet can still save you.
The hope in that case is that the enemy sensor operator will lose track of your sub with all the water currents, exploding DCs, strong winds and waves and maybe even schools of fish or pods of whales. But the more enemy ships searching for you, the harder it is to get away. Whichever ship is on the attack run will be receiving radio updates from the other ships, and round and round the ASDIC pings go, just like a ball among the players on a football field. That's why I said that your survival in that case boils down to your experience and skill. To know when to run silent and deep, and when to just "book" it.

[Sailor Steve]

I invariably go to 70 meters and silent running. When I can hear their propellers closing in on an attack run I go to flank, turn hard in the direction of the attacker and drop another 20 meters. They pretty much always miss. Then back to silent. Once I get deep enough I come back up and do it all over again.

[Rambler241]

Simdude wrote:

but 'ahead slow' IS 2 knots, sir?!

Not in any SH3 boat I've commanded. "ahead slow" results in just over 3 knots, loud enough to be heard, though the likelihood of detection depends on depth, whether you're astern (or abeam but just astern) of the hunter above, surface conditions etc. There have been a number of threads here on the subject of speed and detection.

I take your point about the torpedoed merchant, but you still had time to fire "half dozen cannon shots" as you said above. I'm not criticising you at all, just sayin'.

[Plumber1]

I'm with SimDude on that. In my VIIB ahead slow submerged is always 2 kts max.

[Fahnenbohn]

Originally Posted by Sailor Steve

When I can hear their propellers closing in on an attack run I go to flank, turn hard in the direction of the attacker and drop another 20 meters.

And in the same time, don't forget to drop a sound decoy. Conseil d'ami !

[Kip336]

I have mixed feelings regarding diving deep.
Later in the war, depth will not help much in regards to not being found with the improved ASDIC.

In 1943 (I believe, atleast, 'later' in the war) U-boat commanders where ordered to stay at periscope depth so they would be able to use the periscope to improve their, and keep their situational awareness.
That's very handy (I do that sometimes)

On the flip side, diving deeper gives you a few seconds more to dodge any incomming depth charges as they take longer to fall to the correct depth.

I end up using a mix of both, depending on how close they are, and how many there is

[Rambler241]

Plumber1 said:

I'm with SimDude on that. In my VIIB ahead slow submerged is always 2 kts max.

Nope - SH3 vanilla or v1.4, training mission, type VIIb, submerged, "ahead slow" settles down to 3.5 knots. Type IIa runs at exactly 3 knots, type IId runs at 3.5 knots, as does type IXC.