shadow zone

[JUSTSOMEDUDE199]

I hear something about you can go under and not be radar detector but i not seen it come up in the eye and i been 220m down how far do worry if i go more my sub will blow

[Bowfin]

Shadow zone is a thermal layer, it happens when the water changes temperature drastically. It reflects the sonar wave and makes it difficult to locate you. Some games in the pass have told you when you pass a thermal layer but I haven't seen anything in Uboat that informs the player of one. Maybe a tempature gauge we've overlooked?

[JUSTSOMEDUDE199]

ok thanks so it not how deep i go it the temp i need to look for

[r4y30n]

Modern subs continuously log temperature and salinity vs depth for this purpose but I’ve never seen it in a WWII game, I’m not sure they had the equipment to do so.

Either way, devs have made clear that they want underwater acoustics to be as accurate as possible so this effect may be modeled but not directly visible to the player. Could be you need to man the hydrophones and listen for a change in the noise from a contact.

[VP]

If you're below 150 m there is a chance to get a damage. The deeper yor boat the higher chance to get it. Once I dot hit when I was 260m. My boat got alot of water whilst a pump has zero efficiency at this deep and my boat got to below 290m (maybe 50+ deeper even) I ordered to engines full ahead and to dry ballast tanks. It saved me.

[Buster Scruggs]

Originally posted by JUSTSOMEDUDE199:

I hear something about you can go under and not be radar detector but i not seen it come up in the eye and i been 220m down how far do worry if i go more my sub will blow

I think the Shadow zone has a chance of spawning from 240m+ but it varies

[Twelvefield]

I'm going by memory, but didn't WWII American crews drop a probe on a line to ascertain the thermal? You'd have to be on the surface to do that. I don't believe the U-boats used those probes. My recollection is that U-boat captains did mark their charts with anecdotal information, and perhaps the surface fleet did probe for thermals.

[wolf310ii]

Originally posted by Twelvefield:

I'm going by memory, but didn't WWII American crews drop a probe on a line to ascertain the thermal?

The US had the Barythermograph to measure the temperatur and depth as a probe for destroyers. US Submarines had a thermometer built in.

But even without measuring the temperature or salinity, a U-boat could find a thermal layer, because of the change in buoyancy (an u-boat can even "swim" on the thermal layer) or with the hydrophone (if the u-boat is in the shadow zone, the destroyer is too)
A few weeks ago i saw an interview of a u-boat captain, were he explained how he used the thermal layer in the mediteranian sea to hide

[DECAFBAD]

The GHG manual talks of water stratification affecting listening ranges. They were certainly aware.
https://www.cdvandt.org/GHG-AN301-Beschreibung.pdf

The shadow zone happens in very specific scenarios
It can happen at dawn when the cool air causes the sea to be colder the closer you get to the surface, then sound sources near the surface will be inaudible at rather close distances.

It can also happen during day when the sun heats up the surface layer, causing sound to curve upwards. Evaporation causes salinity to go up, pushing the hotter seawater downwards. How deep this water goes determines the layer depth.
If below this layer sound curves downwards because of the deep water being colder, then you will have a shadow zone below the layer at distances of a few kilometers.

[PafunaMT]

Originally posted by wolf310ii:

Originally posted by Twelvefield:

I'm going by memory, but didn't WWII American crews drop a probe on a line to ascertain the thermal?

The US had the Barythermograph to measure the temperatur and depth as a probe for destroyers. US Submarines had a thermometer built in.

But even without measuring the temperature or salinity, a U-boat could find a thermal layer, because of the change in buoyancy (an u-boat can even "swim" on the thermal layer) or with the hydrophone (if the u-boat is in the shadow zone, the destroyer is too)
A few weeks ago i saw an interview of a u-boat captain, were he explained how he used the thermal layer in the mediteranian sea to hide

Hey Wolf, is that article resource online? I’d love to get a hold of it. Also, what are your preferred archives for research? Thanks kindly in advance sir.

[wolf310ii]

Originally posted by PafunaMT:

Hey Wolf, is that article resource online? I’d love to get a hold of it. Also, what are your preferred archives for research? Thanks kindly in advance sir.

That wasnt an artikel, it was an video on YT:
https://www.youtube.com/watch?v=wUa7CHzPSks
Gerd Kelbig captain of U593 talks about the "themal layer" (he says salinity, but the effect is the same, change of density of the water) at around 1h 5min.

My preferred source for research are primary sources, like manuals, KTBs, ect.
Here is a site with lots of them:
https://archive.hnsa.org/doc/index.htm
Here a Site with lots of H.Dv about munition:
http://michaelhiske.de/Wehrmacht/Heer/Merkbl%C3%A4tterMun/StartSeite.htm
Uboatarchive has also a few good documents:
http://uboatarchive.net/Manual/GeTechDocs.htm