Cavitation and Acoustics in SH3

[Pillar]

Do the propellers of these old WW2 boats always cavitate, even at low speed? The graphic always shows bubbles coming off them, it looks like they are always cavitating.


Is there any modeling of the thermal layer? If so, where is it normally approx?


I'm trying to learn a bit about the acoustics as I'm not having much luck surviving destroyers in 1944. The usual pattern is that once they locate me for the first time, I can never "shake" them. I can usually do pretty good to avoid being hit by depth charges, but it will go on forever.

I've tried just sneaking away at silent running and slow speed after a depth charge run, and they always pick me up on active sonar. I've tried sprinting, but that really never helps. I don't know if they are just hearing my prop or are picking me up on active still. I've also tried brief sprints while the charges are booming, with course changes opposite to the direction the destroyer turns after his run -- nadda. Even bottoming the boat and cutting the engine didn't work out, because they pounded me with active. (Depth was about 150m)

One time I got lucky in an XXI (cheating, I know). I used 1/3 (one bell faster than slow) and must have got out of his active sonar range while still remaining quiet enough for his passive sonar not to hear me. However, I found "Slow" didn't get me far enough away from the Destroyer before he pounded me with active again, even in the XXI.

If anyone has any advice and can help me understand how the acoustics work I would most appreciate it.

[Einzelganger]

As to what U-Boats did in reality i'm no expert so i'm afraid i can't help you with your first question.

As for the thermal layer i've read a lot of post about it and it just isn't modelled in the game. I believe even a modder tried to look for it within the game files but didn't turn up anything.

I've played out one career until the end of the war and certainly from 1944 until the end it can be a real challenge to evade those DDs.

One way is to change course and increase speed directly after the first depthcharges have been dropped. As you are now behind the destroyer it has lost you for a while and in the noise of exploding depthcharges it gets more difficult for them to hear you. Once this is over return to silent running and hope for the best. Also, you have countermeasures available to you ( Bold ) which could fool them into thinking you are still in a previous position

During all this another point is to change depth every now and then. I've found that going deep and eventually coming up again can also loose them. But nearing the end of the war it can get a real challenge.

[Redwine]

There is an amazing topic about Dds pinpoit attack with 32 pages, , use the forum search...

That topic join people who had two main problems, Dummy DDs/DEs and Uber DDs/DEs.

Many diferent mods result from that topic solving the main cases.

I made my own, i was experimenting Uber DDs/DEs problem like as you.

Finally i obtain a very good silent running protection against pasive hydrophones, it not give protection against active sonar pings, we need thermal layers, but saddly they are not modelled into the game.

Plus i introduced a new setting taked from another file where it works, Aspect factor.... it is suposed to reduce the detection according the aspect of the sub, you will be less detected from front and back..... not sure if works fine, but i note i am able to shake them when i maintain the red lines in the map always at my back when scaping.

If you want to try my settings, here you have :

http://rapidshare.de/files/13095320/DDs_Detection_13b_Stage.zip.html

I dont made the changes aiming historical values, instead i was aiming historical behaviour and survability provabilities.

Be sure you had not modified the sub speed for ahead slow setting, into uboat .cfg file. When you hit foe silent running be sure your sub go to slow speed under 3 knots. If not go to the sub folder and change the percent value for ahead slow, 0.40 for all subs and 0.15 fot type XXI.

CB discovered a line wich changes the DDs behaviour, this line control the time that DDs was looking for you after losse contact on you.

As long is the setting as long the time they stay looking for you, as short is the setting, as quickly they abandon the hunt on you and return to the escort position.

Look into Sim.cfg file :


[AI detection]
Lost contact time=15 ;[min] Long makes DDs and DEs stay on hunt

If you set the time to 5, they back to escorto position after 5 minutes they losse contac with you.

Be ware, some masive mods introduce a random behaviour in this time rising it up to 45 min, then you will have a nightmare and a neverending hunt on you if you dont reach to stay undetected by 45 min.

If at 40min you are detected, the time is reset to zero and you will have another 45 min.

I used 15 min...... works fine.

Sadly we can not discover how to make DDs and DEs have a diferent behaviour, in example, DEs must to prey on you about few minutes, enforce you to submerge and back quickly to escort position.

DDs must to prey on you, and maintain serach for you a complete day or more.

Sadly we have only one choice.

:up:



>>>>>>>>>>>>>>>>>>>>>

Mod is not finished, i need to take hands over some points, in example i was thinking in to reduce ramdom factor on depth charges explosions, i was in the game but is unreal, the matter is i don want to fall into make the game so easy.

Plus i am thinking into introduce a some kind of thermal layer protection, if you make deaf one sensor under determined depth, you will be protected, the matter is, the protection is absolute, you will be no detected at all, and thermal layer diminiushed the detection but not at all.

Another posibility is to make deaf only one sensor, in example active one, in example under 200m, then you can be detected by pasive one but not by the active one.

But all these are only future posible changes, the mod as it is now V13b, works fine, and give you a good silent running protection, off course, you can hunt anything submerged depth and at silent running speed, if you want to hunt some thing, you must to take risks...........

:up:

[HEMISENT]

Hi Redwine
I've also been kicking around an idea for thermal layers. If you have the AI_Sensors.dat file height settings for active/passive max depth settings set to 200m(your example) this means that at all times that was an absolute setting-you dive below 200m and its pretty much guaranteed you will lose detection.
Using this idea how about making multiple copies of the AI_Sensors.dat and each one has a different height setting, maybe 5 copies total. Then using SH3 Commander and the Random folder structure insert them in there.
I have 10 random folders right now. if I insert these 5 seperate AI_Sensors.dat files that means that I have 50 percent chance of getting some form of thermal layer and 50% chance of sock settings.
This can be set up by date also in Commander.
Let me have your thoughts on this if you think it's worthwhile.

Cheers!

[Pillar]

I think that's a really good idea. It's messy, but it works.

[NeonSamurai]

As for destroyer and depth charge evasion, here are some tips.

1. Always try to go as deep as you can, the deeper you are the longer it takes the ash cans to reach your depth, the more chance you have to evade them. Also depth helps with evading detection some.

2. generaly use silent running at 3 knots (3-5 if your in the XXI). When the Destroyer makes his run (you will hear the engines over head and the pinging will have stoped) go to ahead flank, turn off silent running (so you can repair during the run) and turn hard into the direction of the DD, once the ash cans stop detonating, go back to silent running at 3 knots. Driving away from the DDs.

3. In very shallow water (50m or less) you may want to consider fighting them off, as you have little other choice, a bunch of wasted torpedos is far better to a destroyed boat. Personaly i try to avoid shallow water engagements with destroyers around.

4. Alternating depth can help throw off the DD's run. Generaly best done when at flank speed as you change depth alot quicker. If your realy deep you can also blow ballast (emergency surface) and set your depth at least 50-100m below the surface (blowing balast will make you climb at least 50m), just be sure not to run out of compressed air, and not to pop onto the surface.

5. Try to conserve battery power, only use flank when you have to. Its not unknown to have to spend many hours avoiding depth charges before they finaly give up.

6. Try to position yourself so the dd(s) cant make a run on you from the stern of your boat. Idealy try to keep them at your 90/270 degree line (left side or right side), or if you can try going head on (this tends to mess up their run as they will usualy drop too late). 90/270 is best though as you will tend to avoid most to all of the pattern.

7. When the enemy is pinging looking for you, your best off either pointing your bow or stern at them to lower your sonar profile.

&. When the DD's loose contact with you they will start droping depth charges randomly, this is the time to try to escape by driving directly away from them with silent running at depth. Try to keep your sonar profile as small as possible by keeping your stern pointed at them (see 7.)

[Church SUBSIM]

If you want to try my settings, here you have :

http://rapidshare.de/files/13095320/DDs_Detection_13b_Stage.zip.html


Redwine,

I am using IUB 1.02 and NYGM Ship Damage Mod. Do you know if these adjustments you have made to the sensors will work with those two mods?

I would very much like to try them out.

Thanks,
Church

[Redwine]

Hi Redwine
I've also been kicking around an idea for thermal layers. If you have the AI_Sensors.dat file height settings for active/passive max depth settings set to 200m(your example) this means that at all times that was an absolute setting-you dive below 200m and its pretty much guaranteed you will lose detection.
Using this idea how about making multiple copies of the AI_Sensors.dat and each one has a different height setting, maybe 5 copies total. Then using SH3 Commander and the Random folder structure insert them in there.
I have 10 random folders right now. if I insert these 5 seperate AI_Sensors.dat files that means that I have 50 percent chance of getting some form of thermal layer and 50% chance of sock settings.
This can be set up by date also in Commander.
Let me have your thoughts on this if you think it's worthwhile.

Cheers!

Good..... :up:

That sounds good, is just another way, but the bad point of this trick is the sensor become "completelly" deaf under that setting, and a thermal layer dont deflects all the sound, instead a big percent of this only.

Another way is to make it only in one sensor, may be active or may be pasive..... :hmm:



Using this idea how about making multiple copies of the AI_Sensors.dat and each one has a different height setting, maybe 5 copies total. Then using SH3 Commander and the Random folder structure insert them in there.

I never used SH3 Commander, really i have not idea about how its works or what posibilities it have ........ :hmm:

:up:



If you want to try my settings, here you have :

http://rapidshare.de/files/13095320/DDs_Detection_13b_Stage.zip.html


Redwine,

I am using IUB 1.02 and NYGM Ship Damage Mod. Do you know if these adjustments you have made to the sensors will work with those two mods?

I would very much like to try them out.

Thanks,
Church


I am using it with NYGM Ship Damage...... any way i made my changes, but i think so there is no uncompatibility.

I dont know IUB Mod, i dont use it, i dont like masive mods, may be it is so good, but i dont use any masive mod, i like to make small changes one by one.

But it think so IUB changes similar files....... just back up yours and try.... if dont like it, just roll back.

Any way, if there is any uncompatibility, the only you will change is the detection behaviour and survival probaility..... the others IUB changes will still there.

:up:

[Church SUBSIM]

Thanks Redwine - appreciate the feedback! And thanks for posting the tweeks - look forward to them!

[HEMISENT]

I never used SH3 Commander, really i have not idea about how its works or what posibilities it have ........ :hmm: .

Redwine, with Commander you can have a single particular file be inserted
in a dated folder and when that date arrives that particular file is activated.
or: you can have a particular file inserted in a random folder as in my example and have it activated by date. There is no limit on the amount of random folders you can have, right now I have 10 but I could have 20 if I wanted to increase ratio.
What I'm thinking of trying is to make 5 or 10 AI_Sensors.dat files with different height settings. Some would include both active and passive heights being edited, others would have only one or the other edited.
Then plug these into the random structure and see what happens. I would have no way of knowing if one of the random files was used or not and certainly no way of knowing which particular edited file was in use. Only by diving would tell and then I would not know if it was a "thermal layer" I found or just an enemy DD that lost me and left.
Certainly not as good as if thermal layers were actually modelled but the behaviour might be acceptable.

I highly recommend you try SH3 Commander as it opens up a whole new world for this game

[Redwine]

@ Hemisent :

Many thanks for info, well i installed the SH3 Commender yet now, but not, i dont like any program wich touch my files without my permision..... sorry.

Any way for those users of this program, your idea is excellent !!

Why you dont make a set of premade folders with good setings and release them for share as a mod for SH3 Commanders users ?

Go ahead, your idea is so good in my opinion. :up:

[HEMISENT]

@ Hemisent :
Why you dont make a set of premade folders with good setings and release them for share as a mod for SH3 Commanders users ?
Go ahead, your idea is so good in my opinion. :up:

The theory is valid and I'm just about wrapped up with something else so I guess this is next on the list. The problem is my AI_Sensors file is so cobbled up I have no clue whats original anymore. I'm using a mixture of Caspofungin's settings for early war and then CB's + my own for mid and late war. Once I test this all out I'll probably submit a post detailing how it can be done providing of course everything works as planned. "The best laid plans of mice and men...etc, etc."
Also, the problem with doing this is that lets say this does work and there are numerous edited copies in thr random folders. the first time you enable a fresh mod that uses that particular file Commander may or may not over ride it-something else to think about

[Redwine]

The theory is valid and I'm just about wrapped up with something else so I guess this is next on the list.

It was my next on my Detection job, but i was not sure about it, if tweak one sensor...... then wich one ? or both.

The matter because i am not sure, is because, it really nerf a sensor, make it deaf completely, and it is relly not a capability of the thermal layer, plus when you know at which depth it is adjusted, it become not too interesting.

But your way, with random and never know settings sond better.

Let me know if you need some thing. :up:

[Kilamon]

Why not get the answer about thermal layers from Herr Jurgen Oesten himself? He was there! ftp://ftp.ubi.com/uk/silenthunteriii/videos/Oesten_Thermal_layer.zip