Depth keeping below 180m

[Hoster]

Hello,
I know that there was a lot of talking about the depth keeping problem in SH5, but as far as I noticed it, there`s nothing about the depth keeping below 170m. To the point: When I`m diving below aproximately 180m, the depth is only stable at 3 or 4 knots. So in silent running, the boat starts to dive until crash depth is reached. Until now it makes no sense to me to dive below 170m because I have to leave silent running to stabilize the boat - but the destroyers than have a easy task to locate my position. Is there a mod available, where it is possible to dive for example to 200m with a depth stabilized submarine at 1 or 2 knots?
Thanks for help!

[volodya61]

stoianm pitch&roll for SH5 - http://www.subsim.com/radioroom/showthread.php?t=183306

TDW Depth keeping problem - http://www.subsim.com/radioroom/showthread.php?t=179746

[Hoster]

Thanks,
but I`m already using the mod you mentioned. They keep the depth up to 170m, but not below.

[TheBeast]

Originally Posted by Hoster

Thanks,
but I`m already using the mod you mentioned. They keep the depth up to 170m, but not below.

Only reason for this that I can think of...

Below 170m, leaks begin to overwhelm pumps. If boat does not maintain enough speed, it will begin to sink. The deeper you go, the faster it seems to sink or slip away.

Does this sound logical?

[Hoster]

It seems, that nobody else but me is facing that problem mentioned above. Well the sub is in perfect condition with no leakings at all, but I can only hold depth below 180m at 3 or more knots. I thought it is a bug concerning everybody...

[Trevally.]

Originally Posted by Hoster

It seems, that nobody else but me is facing that problem mentioned above. Well the sub is in perfect condition with no leakings at all, but I can only hold depth below 180m at 3 or more knots. I thought it is a bug concerning everybody...

See this thread - It may help you http://www.subsim.com/radioroom/showthread.php?t=179746

Download here http://www.gamefront.com/files/21093845

[0rpheus]

Originally Posted by Trevally.

See this thread - It may help you http://www.subsim.com/radioroom/showthread.php?t=179746

Download here http://www.gamefront.com/files/21093845

Trev - he's using that already. His problem is depth keeping at low speed below 170/180m. I assume you're thinking of this post: http://www.subsim.com/radioroom/show...7&postcount=93

However - even with TDWs mod, you have to do 2-4 kts to maintain depth below 170, and that's too fast for IRAI - they hear anything above about 1 kt, so going deeper than 170 (risking crush) to avoid cans ends up being counter-productive: you make more noise than if you'd stayed at 160 or so, and they hunt you down all the harder.

I've never been able to figure out how historically accurate this effect is. I understand that buoyancy should drop below a certain depth (I think), but I also assume subs would have gone lower than 170 in some circumstances (and survived). Any history buffs have anything to weigh in?

I think in SH4 I can hold depth well below test depth at 1kt - whether that's realistic or not, I couldn't say. At the moment in 5 (with IRAI), there's no point - stay above 160/70 and be quieter, or go below that and be a lot louder. You can't win

[Hoster]

Thanks Orpheus, you got me absolutely right! Well I read, that the VIIc/41 could dive to 260m! Very often subs were forced down to 200m and much more (with silent running).
I´m using a lot of mods including Open horizon, IRAI, the U-boat historical modification mod....

[Hinrich Schwab]

Originally Posted by 0rpheus

I've never been able to figure out how historically accurate this effect is. I understand that buoyancy should drop below a certain depth (I think), but I also assume subs would have gone lower than 170 in some circumstances (and survived). Any history buffs have anything to weigh in?

From what I know, the boat would have to manually adjust trim to compensate both weight and air compression due to Boyle's Law. When coming back up, the trim and air pressure levels would have to be vented to avoid rupturing the tanks as the air pressure increases as depth decreases. Even then, I would hazard a guess and think that at least 2-3kts would still be needed. However, the issue is possible cavitation and sound propagation at that depth. Active sonar, especially late war should still have little issues with a boat at ~180-200m. However, water pressure should allow a boat to operate at faster speeds without passive sonar picking the boat up. I know the Sonalysts sims model this, but I do not think any of the SH games do. Add thermoclines to the mix and there are all kinds of fun variables that should be in play, but the sims either do not deal with or oversimplify to a degree that either gives too much favor to either the sub or the destroyer, depending on game and instance.

I know that this copy of the Type VIIC manual has all kinds of fun performance data with sound propagation and detection.

http://www.uboatarchive.net/Manual.htm

[0rpheus]

I think it's cavitation that's the problem, at least in terms of being heard at that depth. Active is of course a different kettle of fish, but based on my time with Dangerous Waters and the way propeller noise changes with depth, the lack of cavitation modelling in SH5 would mean you make the same amount of noise regardless of depth - so where in RL, you might be inaudible to passive sonar at 200m doing 2-3kts due to the extra water pressure, in the game you're making as much noise as those 2-3 kts would make if you were at periscope depth.

If that's the case, then the only solution would be to allow the sub to maintain depth at lower speed (below 2kts) at depths lower than 170m - it's the only way to account for the cavitation variance short of actively reducing how much noise the sub makes when it hits a certain depth (which to me sounds much more complicated).

Since I don't have SH3, could someone tell me if SH3 allows you to maintain depth with 1kt below 170 metres? If SH3 does, and SH4 does, then why not SH5?

[THE_MASK]

I dived to 180mts in my VIIB and went 1 knot . It wouldnt hold depth but sank very slowly . I will check my mod soup . In the submarine sim file \unit_submarine it seems to be the relationship between the mass and the submerged displacement .

[0rpheus]

Originally Posted by sober

I dived to 180mts in my VIIB and went 1 knot . It wouldnt hold depth but sank very slowly . I will check my mod soup . In the submarine sim file \unit_submarine it seems to be the relationship between the mass and the submerged displacement .

It's definitely something to do with submerged displacement, I remember TDW saying so in his Depth Keeping Mod release thread, where I've raised this issue before. Modifying the files is beyond me though, I've not got the skills even if I did have the time!

PS - def not a mod soup issue - I've had this with every mod combination I've ever used. TDW fixed it to a degree with the Depth Keeping Mod, it just needs to go a little further

[Hinrich Schwab]

Originally Posted by 0rpheus

...the lack of cavitation modelling in SH5 would mean you make the same amount of noise regardless of depth - so where in RL, you might be inaudible to passive sonar at 200m doing 2-3kts due to the extra water pressure, in the game you're making as much noise as those 2-3 kts would make if you were at periscope depth.

Precisely. This is the root of the problem. If there was a cavitation-noise propagation model, the speed to buoyancy ratio would be moot as one would be able to maintain the necessary speed to hold depth without the extra trimming that would be dictated in real life to either maintain depth or reduce the descent to a crawl.

If that's the case, then the only solution would be to allow the sub to maintain depth at lower speed (below 2kts) at depths lower than 170m - it's the only way to account for the cavitation variance short of actively reducing how much noise the sub makes when it hits a certain depth (which to me sounds much more complicated).

In SH5, it is not that complicated because there is already the noise reduction "skill" in stock. The function is there, it is just using it differently.

Since I don't have SH3, could someone tell me if SH3 allows you to maintain depth with 1kt below 170 metres? If SH3 does, and SH4 does, then why not SH5?

Last time I played SH3 w/GWX, I noticed no issues. I will load it up again to test it. Should I notice anything different, I will update this section of the post.

EDIT: Type VIIB boat. Ordered normal dive at Ahead Full. Ordered level at 170 meters. Descended to 195 meters and leveled off. Reduced speed to Ahead Slow. Dove to 180 meters. Ordered Silent Running. No depth change@ 2 knots. Ordered All Stop. Boat dropped to 181 meters at 1 knot. 10 minutes after ordering all stop, no depth change. The extra meter is an acceptable trim variation. SH3 w/GWX hovers at 180 meters. Did not take boat deeper during this test, but I can assume that it is still stable at 200 meters.