Some Points / Questions About Depth

[Stevepine]

Originally Posted by Shadriss

I did a lot of reading (a long time ago) on WWII US boats, and while I understand that we're talking the German side, I think the designs are similar enough that the depths should be similar.

First - a meter is ROUGHLY equal to 3 feet. I know thats not exact, but its close enough for this discussion. (3.3 is closer, but I hate decimals.) US Boats at the time didn't like going below about 350 feet, so call that about 117 meters. Theoretical crush depth was 600 ft (or about 180 meters). Now, in extremis, a boat skipper would try anything, so going deeper than that would still be an option if he felt he had no choice. Being DC'd would definately qualify.

200 meters (660 ft) would be seriously pushing it, and he likely went that far down simply because no Skimmer Skipper would think a U-boat would even try anything that deep. Hence, he's relatively safe. 210 (just short of 700 ft) is nearly insane. Note he only did that ONCE.

Now, all that said, the second part of that question is a much easier question. DC's are ALWAYS a realistic danger to a sub. No matter the depth. It isn't the depth that they are set to, but how CLOSE to the boat they explode. DCs rely purely on the shockwave to shake the sub apart. So, if the sub is at 210 meters, and the DCs are dropped to 210 meters, and they are close enough, they will be as nasty as they would be in shallower depths... in fact, they may be MORE effective given the non-compressability of water and the water pressure at that depth.

Hope that gives you some insight...

Thanks for the reply! really interesting to see those crush depth figures you gave.

With regard to the D. charges I was just thinking that deeper would be safer because... surely the deeper the sub is the harder it must be for a destroyer to drop charges accurately and with precision?

Therefore I was wondering how dangerous DCs could really be to a U boat at a 180 - 200 meters. Would be quite hard for the destroyer to drop them down to that depth accurately I think. (although im sure a really skilled destroyer crew could manage it)

Plus in SH5 , Im sure the AI would need tweaking to make DC s accurate at that kind of depth??

[TheDarkWraith]

Originally Posted by Stevepine

Plus in SH5 , Im sure the AI would need tweaking to make DC s accurate at that kind of depth??

They are accurate to whatever is specified in the .sim (or .zon) file for the DCs (DepthPrecision)

[Shadriss]

I think he was refering to IRL, TDW.

On on that front, DCs of WWII were set to detonate on timers, as I recall. All one had to know was how fast the sink rate was, so some quick calculations, and set the timer.

ALternately, they may have detonated on a pressure sensor. Since pressure is a constant as you go deeper (IE< the pressure for 100 ft will ALWAYS be the pressure for 100 feet, no matter where you are in the world...), all you'd have to do is, again, set it's depth (pressure) timer.

Accuracy is another thing altogether. Especially in that era, Active Sonars were of limited use. (Actually, that's still true today... for referance, I am an USN STS1/SS on the ALABAMA atm...). They can give a real good indication of bearing and range, but depth is pretty much a guessing game.

That said, as I kind of hinted at in my first reply, ships are known to use given depth bands. WWII boats just cruising around rarely went deeper than about 200 feet. During a periscope attack on a surface convoy or singleton, he'll stick with PD as much as possible, and then if forced go deep to the depths we talked about earlier. However, because he's speed limited (dont want to be TOO loud, after all...) his ability to change depth quickly is hampered. So, if you have a good idea of range and bearing, and a good feel for how long it's been since he left PD (or if he's still there), you can make a pretty good educated guess.

[Stevepine]

Originally Posted by Shadriss

I think he was refering to IRL, TDW.

On on that front, DCs of WWII were set to detonate on timers, as I recall. All one had to know was how fast the sink rate was, so some quick calculations, and set the timer.

ALternately, they may have detonated on a pressure sensor. Since pressure is a constant as you go deeper (IE< the pressure for 100 ft will ALWAYS be the pressure for 100 feet, no matter where you are in the world...), all you'd have to do is, again, set it's depth (pressure) timer.

Accuracy is another thing altogether. Especially in that era, Active Sonars were of limited use. (Actually, that's still true today... for referance, I am an USN STS1/SS on the ALABAMA atm...). They can give a real good indication of bearing and range, but depth is pretty much a guessing game.

That said, as I kind of hinted at in my first reply, ships are known to use given depth bands. WWII boats just cruising around rarely went deeper than about 200 feet. During a periscope attack on a surface convoy or singleton, he'll stick with PD as much as possible, and then if forced go deep to the depths we talked about earlier. However, because he's speed limited (dont want to be TOO loud, after all...) his ability to change depth quickly is hampered. So, if you have a good idea of range and bearing, and a good feel for how long it's been since he left PD (or if he's still there), you can make a pretty good educated guess.

Thanks ,that's really insightful. I didnt know that when they set the depth for depth charges it was done so much on pure timing and instinct.