U-48 won't hold depth

[Zosimus]

During an approach on a convoy I was spotted and had to break off. I was repeatedly depth charged and one shot hit me as I was 99 meters under. I started sinking and had to abandon silent running to clean up the mess. I was going down so finally I blew emergency at 148 meters and started coming up again. Flood recovery was managed and after 6 hours of underwater fun the escort went back to his convoy. I surfaced with about 20% battery power, 30% compressed air, and CO2 over 2. What a joy to have air again!

So I started following the escort back to his convoy at about 7000 meters when I ran across a lone ship on my way. I determined its course, speed, and set up for the shot but the problem is the sub won't hold periscope depth at ahead slow. Unless I'm going at least a third it will head steadily toward the bottom. Is this a bug or am I just damaged? Everything has been fixed except the observation scope. That's kaput. All the water's been pumped out, dive planes seem normal and I can't tell you what my hull integrity is because I don't know. I managed to make the shot by circling 360º and popping up on the other side with the deck gun to finish him fast.

The convoy is nearby and closing. If I can't maintain periscope depth, I'm just going to head back to Wilhelmshaven and call it a patrol.

Five torpedoes remaining: 3 in front, 2 in back.

[maillemaker]

I've seen this behavior before. I vaguely recall something about problems if you interrupt a crash dive?

For me I think generally once you get back to the surface the problem goes away?

Steve

[Nukesub]

I have encountered a similar situation. I was at 150m in a Type VIIB and had just been depth charged. Didn't have any drastic damage but I noticed I could not keep depth unless I was at 1/3 speed as well (I typ. try to run at 1 knot if I'm being hunted).

[captgeo]

To be honest I think you are over aggressive as a capt, why would you go back after the convoy with damage?

The " problem " that you have is the damage must have been extreme, next time retreat and call it a day untill you can be repaired,

[Sailor Steve]

Any hull damage and loss of integrity will limit your capacity to hold depth. You need to head for home and get it repaired.

[UKönig]

I guess I have been lucky, but I have never experienced a situation in which the boat was diving out of control and could not hold depth, that wasn't a direct result of damage to the pressure hull. And/or taking too much water in places that are not supposed to have water.

[Zosimus]

Originally Posted by captgeo

To be honest I think you are over aggressive as a capt, why would you go back after the convoy with damage?

The " problem " that you have is the damage must have been extreme, next time retreat and call it a day untill you can be repaired,

There are two very important reasons for reengaging the convoy.

First, it's my duty to defend Deutschland against her enemies and that involves sinking ships. I have eels, and I see ships.
Second, the frigate in question is out of depth charges. At one point during my attempt to give it the slip I came to 25m at flank speed then ordered silent running and tried to evade it before my fine boat went too deep. During this adventure the escort simply buzzed around angrily above my head and pinged me.

[BigWalleye]

The NYGM physics model assumes (slight) negative buoyancy. If you try to "hummingbird," you will slowly increase depth. You can't, for example, hover at periscope depth. With no way on, the boat will slowly settle and put the 'scopes underwater. Same is true at any depth.

GWX is supposed to use positive buoyancy. The boat will rise slowly, and broach at periscope depth with engines stopped. That is what the documentation says, but I've never seen it, and I have hovered throughout a looong submerged attack. (Aside: This is one reason I play NYGM and not GWX. Submarines did not hover. It is theoretically possible for an elite diving officer to hold the boat stationary, but I do not know of a single example of this actually being done operationally. If anyone knows of a counter-example, please post it! I'd be delighted to know about it.)

Stock game has neutral buoyancy. 'Nuff said.

Stiebler's patches include the "Silent Running Fix" which makes it difficult to hold depth when silent running. (As Stiebler explains, in silent running, all pumps are switched off. At low speed (0-2 kts), the boat will settle, especially at depths below 100 m. The hull is not perfectly watertight and is compressed by the increasing pressure at depth, decreasing the displacement.) This settling is more dramatic than the negative buoyancy effect of NYGM, and requires some interesting (and historically appropriate) tradeoffs by the boat commander: Do I turn the pumps on, and attract attention with the noise? Do I speed up, and attract attention with the noise? Or do I just keep drifting slowly deeper and deeper? BTW, the Silent Running Fix works with any model - NYGM, GWX, or stock.

If you are using NYGM, the Silent Running Fix, or both, what you are seeing may result from those mods.

"It's not a bug. It's a feature." - Mark Ryback

[Raptor]

With GWX, I routinely see my VII and IX boats slowly lose depth when running below 150 meters at Ahead Slow. I have to go to One Third speed to stop the descent and the "Approaching critical depth" warning. Going back to Slow causes the descent to begin again.

All this with no hull damage (100% integrity).

[BigWalleye]

Originally Posted by Raptor

With GWX, I routinely see my VII and IX boats slowly lose depth when running below 150 meters at Ahead Slow. I have to go to One Third speed to stop the descent and the "Approaching critical depth" warning. Going back to Slow causes the descent to begin again.

All this with no hull damage (100% integrity).

"Buoyancy and fine-trimming your depth

• The speed at which your U-boat is traveling can affect your depth.

• A U-boat that is non-moving or operating at 2 knots will run about one meter or so above its commanded depth. The top of the conning tower may broach the surface if you were at or just above periscope depth. This could result in ships or aircraft spotting your U-boat if they are in range.

•A U-boat operating at > 2 knots will be unaffected

• GWX varies your U-boat‘s buoyancy after a close depth charge detonation. This may result in your U-boat being temporarily blown to the surface by a depth charge exploding underneath you, or being driven deeper by depth charge explosions just above you

• Flooding will force your U-boat deeper to reflect the effect of flooding on your U-boats buoyancy and trim"

- GWX Manual v3.0, page 48

As I said in my previous post, I have not personally observed the positive buoyancy behavior described in the manual. In GWX, my VIIC can hover like a Huey. Nor have I experienced the lack of depth-keeping you describe. I can only guess that some other factor - perhaps another mod - is contributing to the behavior you describe.

Do you use the Stiebler patches?

[captgeo]

Originally Posted by Sailor Steve

Any hull damage and loss of integrity will limit your capacity to hold depth. You need to head for home and get it repaired.

the above is correct, when you receive damage to your hull, retreat and get repaired, its that simple, never mind the Fatherland stuff

[BigWalleye]

Originally Posted by captgeo

the above is correct, when you receive damage to your hull, retreat and get repaired, its that simple, never mind the Fatherland stuff

I agree, that is the prudent thing to do. But how you play the game is how you play the game. If Zosimus' in-game persona is more aggressive, or less prudent, than yours or mine, that's OK too.

BTW, I have just completed a small experiment, using GWX3:

U-556
27 May, 1941
North Atlantic

0900 Ordered flank speed. Ordered 150 m.

0915 Level at depth. Ordered 3 kts.

1015 Depth 150 m (per command room gauge). Ordered 2 kts

1115 Depth 150 m. Ordered Ahead Slow on ER telegraph.

1215 Depth 150 m. Ordered Silent Running.

1315 Depth 150 m.

Exited mission

During the entire test, the command room deep gauge did not move by as much as 1 meter up or down. Since I used time compression (TC 64), I did not monitor the gauge continuously. Time at accelerated TC was spent at the Nav chart screen. The command room gauge was checked at the hour mark only, at TC 1. The GUI gauge at the Nav chart screen did not vary either, but it is smaller and harder to read accurately.

[Zosimus]

Originally Posted by BigWalleye

"Buoyancy and fine-trimming your depth

• The speed at which your U-boat is traveling can affect your depth.

• A U-boat that is non-moving or operating at 2 knots will run about one meter or so above its commanded depth. The top of the conning tower may broach the surface if you were at or just above periscope depth. This could result in ships or aircraft spotting your U-boat if they are in range.

•A U-boat operating at > 2 knots will be unaffected

• GWX varies your U-boat‘s buoyancy after a close depth charge detonation. This may result in your U-boat being temporarily blown to the surface by a depth charge exploding underneath you, or being driven deeper by depth charge explosions just above you

• Flooding will force your U-boat deeper to reflect the effect of flooding on your U-boats buoyancy and trim"

- GWX Manual v3.0, page 48

As I said in my previous post, I have not personally observed the positive buoyancy behavior described in the manual. In GWX, my VIIC can hover like a Huey. Nor have I experienced the lack of depth-keeping you describe. I can only guess that some other factor - perhaps another mod - is contributing to the behavior you describe.

Do you use the Stiebler patches?

I do not use Stiebler or H.Sie patches. The only mods I have are the crews no medals mod, the flags_enlighten mod, the 16k horizon mod, and the 24th Flotilla Spanish-keyboard mod. I cannot imagine that any of these will result in sinking ships.

The game is saved at the surface within easy hydrophone range of a major convoy to the north and with a solitary ship to the south. Assuming that it's a bug, restoring the game should result in the ship behaving normally. If that occurs, I will attack the convoy. If the ship continues to sink then I'll engage the lone ship to the south.

I'm just off the west coast of England so I still have to go north to round it before heading for home. In the event that the escort starts chasing me again maybe I can torpedo him. Otherwise I have located a small shallow area to the SSE where I can bottom the boat and wait for him to go away. Oxygen isn't the problem–it's the battery power that I need to stay afloat. If I can bottom the boat in <100m water I won't have to spend battery power as I wait him out.

[Zosimus]

Although I saved on the surface and restored after the weekend, U-48 still won't hold depth at less than 4 knots forward. Therefore, I conclude that it's not a bug but rather a result of the damage she took.

[maillemaker]

Undamaged, with GWX3, my sub hovers like a Huey, too.

But my Chief is just that awesome. Sometimes when we flood tanks rainbows come out instead of air.

Steve