SH3's flawed sub physics?[A request]

[Castout]

I just found out that if the Uboat doesn't have sufficient forward momentum while submerged i.e, the speed is very low like 1 or 2 knots, the U-boat will sink slowly but it sinks.

The significance of this is that this means we would not be able to order speed less than Ahead slow which is about 3 knots i.e, silent running is actually not visible in SH3 game world.

Has anybody noticed this? Is there some way to fix this submerged slowly sinking behavior while moving at very slow speeds?

[VipertheSniper]

You haven't by any chance interrupted a crash dive before you observed that behaviour? Because interrupted crash dives cause this behaviour, the speed doesn't really matter I think.

[Castout]

Hmm I don't think I ordered crash dive the last time I tried this out. Ordering less than 3 knots like 2 or 1 knots to simulate silent running would cause our U-boats to sink slowly. You can try to order all stop while submerged(preferabbly at some deep depths like 200m) and you'll notice that your sub will slowly sink to the bottom during all stop. It will start to sink at speed below 3 knots or at ordered speed below ahead slow.

[JU_88]

Its been known about for a while, and is has also been corrected in the past (modded) - but, its certainly not popular with everyone as it makes hunting much harder.
Another boyancy aspect not modelled is that most WW2 sub crews had to fight the controls somewhat after conducting a submerged torpedo attack in order to prevent the sub from breaking the surface due to the sudden loss of wieght.
The early British U-class subs had big problems with this, in fact is was so bad that it led to the 2 external tubes being removed from later versions of the sub.

[VipertheSniper]

Hmm I've never noticed behaviour like this, with GWX not at all because of the positive bouyancy mod, and not in stock SH3 either, although I would've liked to see it like it was in AOD, atleast under silent running, where the boat slowly began to sink after some time in silent running.

[Kpt. Lehmann]

As I recall, there is only one mod that models negative bouyancy. (NYGM)

Using NYGM you must keep a speed of two knots to keep from sinking.

Stock SH3 and other mods use either neutral or positive bouyancy.

Castout, the problem you describe is not related to/does not occur in Stock Sh3.

(Also, if you sub has been damaged and is slowly sinking... this is normal due to flooding/extra water weight.)

[Castout]

Ju_88 you said it has been corrected in mods before, could you point me to at least one? I hate it when my sub starts to sink everytime I try to simulate a silent running.

Yes I'm aware that in RL the boat would try to compansate for loss weight after launching its eel(s) I do not expect a game physics to be that accurate but this incapability to simulate silent running is really fundamental imo especially when DDs are going to detect(hear) our boat much harder if we order a very slow speed. It's just that our boat refuses to float unless it's moving at a certain minimum speed which is totally unrealistic imo. Makes me feel like i'm flying not sailing an underwater craft:damn:

@Kpt Lehmann is it true? it doesn't occur in stock SH3? Okay let me play test this further.

[Kpt. Lehmann]

@Kpt Lehmann is it true? it doesn't occur in stock SH3? Okay let me play test this further.

Yes it is true. In un-moddified stock SH3 version 1.4b, with an undamage U-boat you can come to "All-Stop" and maintain whatever depth you choose.

What is truely needed to represent historical accuracy is the ability of the player to set variable bouyancy, and for compressed air to be used gradually in the effort to maintain a given depth.
This is not possible in SH3. ("not possible" is usually not in my vocabulary)

[Castout]

Yes you're right Kpt Lehmann in stock SH3 you can at least with type IX and type VIIB to maintain depth with very low speeds or at all stop at any depths.


Maybe my first post was specific to type VIIC/41 or I was interrupting a crash dive order.

Yea too bad SH3 doesn't take into account the compressed air used during depth changing. That would be so very cool. Anyone tried to mod this:D?

I have another question more like an idea on modding 'rig for silent running' command, a simple one really but I think I prfer to start a whole new thread for it.

[JU_88]

When I said corrected - I meant negative/positive boyency was added - in stock Sh3 the uboat can hover like a humming bird, just as the Kpt already pointed out.

[Castout]

Yea Ju_88 sorry for my false alarm everybody

[Sailor Steve]

It's just that our boat refuses to float unless it's moving at a certain minimum speed which is totally unrealistic imo. Makes me feel like i'm flying not sailing an underwater craft:damn:
Why would that be unrealistic? At the beginning of the patrol, and every chance they got during it they did re-trim the boat, but any time you're in a position to need to run silent you have likely
1) Fired torpedoes, and

2) Been consuming food, water and fuel without time for a new trim dive.

Both of which will leave the boat likely to either rise or sink. This can be easily countered with the pumps, but when 'Silent Running' the pumps have to be off. In World War Two it was nearly impossible to get a boat to hover without moving, especially in a combat situation. One of the beauties of good old Aces Of the Deep was that after silent running for awhile the Chief would tell you "Captain, it is impossible to maintain depth without running the pumps".

I think the sinking is one of the most realistic mods.

@Kpt Lehmann is it true? it doesn't occur in stock SH3? Okay let me play test this further.
Yes, it's true. In stock SH3 you can hover the boat forever.

[Castout]

Really? Thanks for the history lesson. On my second thoughts I'm actually happy with it sinking...no pumps eh?

Now if the modders can make the interior lights stay turned off for awhile after a close depth charging........"We are at 220m Sir!!!!!!!"
Any way to make the lights off much longer? GUI doesn't need to be messed with. They did already have flashlights. Hey this may be the topic of another thread. I'll make one for this.

Anybody worked on the compressed air mod stuff?

[Wave Skipper]

I do recall reading years ago that subs in WWII had to keep a slight forward movement going in order to maintain a stable depth level. Part of holding to a depth was done by the use of the diving planes which required at a minimum a slight forward motion. I'd have to go back through all the U-boat books I ever read to find the quote. But I recall the words of it everytime I am setting motionless at periscope depth. I am always thinking: this would be impossible in real life.

[linerkiller]

In RL this behavior was caused by small leaks produced by various causes, damages etc. in the lower part of the hull ( italian "sentina") Also in Das Boot, Buccheim wrote that even during the dive, the U boot had to expell water in excess from the boat

[Castout]

so even WWII sub was not a real submersible craft in the sense that they need to have a forward motion in order to maintain depth?

When I see Das boot or U-571 I think I saw them at 0 knots at periscope depth in those movies.

Ouch linerkiller got me first...

So the pump must work in order to maintain depth? So in theory in silent running wheere the pumps are being turned off the boat would keep on sinking with no forward motion.

[PhantomLord]

so even WWII sub was not a real submersible craft in the sense that they need to have a forward motion in order to maintain depth?

When I see Das boot or U-571 I think I saw them at 0 knots at periscope depth in those movies.

Ouch linerkiller got me first...

So the pump must work in order to maintain depth? So in theory in silent running wheere the pumps are being turned off the boat would keep on sinking with no forward motion.

Movies will be movies, will be movies... :D

In RL subs need some forward motion.

"Das Boot" the book describes some techniques to "hang up the boat on the periscope". This is possible without engines running only at absolutly calm sea. You can have some hover effect with endless fine trimming. All has to do with the relation of water pressure outside and water displacement of the boat. You really need the pumps for that. So it´s no option in silent running...

You´ll need an extra physic´s engine for SH3 to simulate all that tiny stuff that really happens in a such complex vehicle like an u-boat. An definitly more men to handle this. Hey that would be a nice idea for MP? Everyone has his station in only ONE boat....

In one of my books (i think it was "Wolfgang Hirschfeld - Feindfahrten / Diary of an u-boat-radio-operator") he talk about another boat that sinks slowly down while submerged at low speed. The crew forgot to open a valve for the depth meter in the command room. So everyone thought they still were at 80 meters. In real the boat was near 220 meters at this time. One man noticed that at his sister instrument in the engine room... i think he got an extra bottle of beer later :D

[von Zelda]

I've found that at 2 knots there is a slight positive bouyancy (approximately 2 meters at periscope depth). So, to maintain periscope depth of 12 to 13 meters, I need to set depth at 14 to 16 meters; otherwise conning tower begins to break the surface.

Is this correct or to be expected in 2.0?

[linerkiller]

so even WWII sub was not a real submersible craft in the sense that they need to have a forward motion in order to maintain depth?

When I see Das boot or U-571 I think I saw them at 0 knots at periscope depth in those movies.

Ouch linerkiller got me first...

So the pump must work in order to maintain depth? So in theory in silent running wheere the pumps are being turned off the boat would keep on sinking with no forward motion.

Movies will be movies, will be movies... :D

In RL subs need some forward motion.

"Das Boot" the book describes some techniques to "hang up the boat on the periscope". This is possible without engines running only at absolutly calm sea. You can have some hover effect with endless fine trimming. All has to do with the relation of water pressure outside and water displacement of the boat. You really need the pumps for that. So it´s no option in silent running...

You´ll need an extra physic´s engine for SH3 to simulate all that tiny stuff that really happens in a such complex vehicle like an u-boat. An definitly more men to handle this. Hey that would be a nice idea for MP? Everyone has his station in only ONE boat....

In one of my books (i think it was "Wolfgang Hirschfeld - Feindfahrten / Diary of an u-boat-radio-operator") he talk about another boat that sinks slowly down while submerged at low speed. The crew forgot to open a valve for the depth meter in the command room. So everyone thought they still were at 80 meters. In real the boat was near 220 meters at this time. One man noticed that at his sister instrument in the engine room... i think he got an extra bottle of beer later :DAnd every day the leitender ingenieur had to mesure the water density ( seawater density change from place to place) and correct the boat's trim ....because in a 750-ton VIIC, also a 1/1000 error led to a notable 750 kg error, and during a crash dive this could be fatal.
To connect the previous topic, Buccheim wrote that during the depth-charge attack the commander ordered the pumps on during the explosion, to avoid detection.....RL is HARD:arrgh!:

[Castout]

Okay okay I got the picture. RL depth control in U-boat is shi*ty hard.

[Sailor Steve]

I've found that at 2 knots there is a slight positive bouyancy (approximately 2 meters at periscope depth). So, to maintain periscope depth of 12 to 13 meters, I need to set depth at 14 to 16 meters; otherwise conning tower begins to break the surface.

Is this correct or to be expected in 2.0?
The last GWX had the positive bouyancy thing. Most people complained that they didn't like it, so they created a fix you could download. I complained that I thought it was a good idea, but with only a 2-meter change it was too easy to counteract. You should keep on rising until you sped up to counter it.

Anyway, the answer is yes. GWX 2 does not have it. Read the link to the changes they made.

[Kpt. Lehmann]

I've found that at 2 knots there is a slight positive bouyancy (approximately 2 meters at periscope depth). So, to maintain periscope depth of 12 to 13 meters, I need to set depth at 14 to 16 meters; otherwise conning tower begins to break the surface.

Is this correct or to be expected in 2.0?
The last GWX had the positive bouyancy thing. Most people complained that they didn't like it, so they created a fix you could download. I complained that I thought it was a good idea, but with only a 2-meter change it was too easy to counteract. You should keep on rising until you sped up to counter it.

Anyway, the answer is yes. GWX 2 does not have it. Read the link to the changes they made.

Right. What we all really need is "variable bouyancy" modelled into SH3... which we can't have. As modders, we can either set for positive, or negative bouyancy... or stay with neutral... but we have to choose.

THere is still some slight positive bouyancy in GWX 2.0, but not as much as before... It is pretty close to neutral now. The trick was to pull this off without losing the cool new surface physics of the U-boats in GWX. In stock they basically just plowed through the water like bricks.:doh: Now in GWX, they toss and roll more appropriately in the waves... and make ya seasick if you turn off the lights.:arrgh!:

[von Zelda]

I've found that at 2 knots there is a slight positive bouyancy (approximately 2 meters at periscope depth). So, to maintain periscope depth of 12 to 13 meters, I need to set depth at 14 to 16 meters; otherwise conning tower begins to break the surface.

Is this correct or to be expected in 2.0?
The last GWX had the positive bouyancy thing. Most people complained that they didn't like it, so they created a fix you could download. I complained that I thought it was a good idea, but with only a 2-meter change it was too easy to counteract. You should keep on rising until you sped up to counter it.

Anyway, the answer is yes. GWX 2 does not have it. Read the link to the changes they made.


Is there a mod for GWX 2.0 to correct or reduce this slight positive bouyancy?

[Kpt. Lehmann]

I've found that at 2 knots there is a slight positive bouyancy (approximately 2 meters at periscope depth). So, to maintain periscope depth of 12 to 13 meters, I need to set depth at 14 to 16 meters; otherwise conning tower begins to break the surface.

Is this correct or to be expected in 2.0?
The last GWX had the positive bouyancy thing. Most people complained that they didn't like it, so they created a fix you could download. I complained that I thought it was a good idea, but with only a 2-meter change it was too easy to counteract. You should keep on rising until you sped up to counter it.

Anyway, the answer is yes. GWX 2 does not have it. Read the link to the changes they made.


Is there a mod for GWX 2.0 to correct or reduce this slight positive bouyancy?

Read my previous post for the answer. We've already taken care of it... looks like we cross posted.

[von Zelda]

Yes, Kpt., we cross posted.

The problem that I had with the original postive bouyancy was in deep dives at slow speeds. I'd have to request depths much deeper than that I wished for just to get the slow moving u-boat deep enough.

My first patrol with 2.0 was to AN81 in a Type II so I haven't had an oportunity to try a deep dive yet.

[von Zelda]

Tried a deep dive at slow speed (2 knots) such as one would use to evade destroyers. There is still a good deal of positive bouyancy so that the u-boat never reaches the requested depth. Must request depth 25 - 50 meters below desired depth.

While it might not be realistic, is there a mod for 2.0 which will result in zero bouyancy like stock game?

As the Captain, I like to request a desired depth and get to that depth; less let the virtual LI figure out the bouyance problem and give me the requested depth.

[Kpt. Lehmann]

Tried a deep dive at slow speed (2 knots) such as one would use to evade destroyers. There is still a good deal of positive bouyancy so that the u-boat never reaches the requested depth. Must request depth 25 - 50 meters below desired depth.

While it might not be realistic, is there a mod for 2.0 which will result in zero bouyancy like stock game?

As the Captain, I like to request a desired depth and get to that depth; less let the virtual LI figure out the bouyance problem and give me the requested depth.

Hmmm, that's really odd as that doesn't occur on my installation and was never reported to be a problem in several months of testing after the adjustment was fielded. I'm not sure what to say other than it appears to be related to your installation somehow. (I'm sure that's not what you wanted to hear.) However, in GWX 2.0 at 1.5 - 2.0 knots while submerged, I've been consistantly able to set any depth in any boat and be within three meters of any requested depth.

Technically, I suppose you could take the stock SH3 1.4b .sim files for the uboats and replace them that way to achieve the old completely neutral bouyancy, but you'd also lose other physics corrective measures relating to engines, fuel consumption, and battery life.

[von Zelda]

Tried a deep dive at slow speed (2 knots) such as one would use to evade destroyers. There is still a good deal of positive bouyancy so that the u-boat never reaches the requested depth. Must request depth 25 - 50 meters below desired depth.

While it might not be realistic, is there a mod for 2.0 which will result in zero bouyancy like stock game?

As the Captain, I like to request a desired depth and get to that depth; less let the virtual LI figure out the bouyance problem and give me the requested depth.
Hmmm, that's really odd as that doesn't occur on my installation and was never reported to be a problem in several months of testing after the adjustment was fielded.

I did not mention it, but I'm using a Type II at the moment. Maybe most of the testing was with Type VII's and IX's?

Went back to my current patrol, requested a dive to 163 meters; after approximately 40 minutes at 2 knots, I reached 129 meters which held pretty constant until I surfaced.

This doesn't affect game play too much anyway. Maybe real Commanders had the same problem with their crews?

[Kpt. Lehmann]

Will keep an eye on the Type II.

Just as a developmental note here, regarding player U-boat physics... the lighter the boat, the harder it is to adjust. Boats with less mass react more sensitively than heavier ones. The Type II's were naturally the most difficult to work on.

That being said, with the Type II on the surface in a storm in GWX... HOLD ON TO YOUR COOKIES!!! That thing rocks and rolls!:arrgh!: