How to maintain depth with zero speed

[joho]

I going down to 180m depth, then shuts down the engines to avoid detection. My sub starts to rise, so I start the engines end go down to 200m stops and the sub starts to decent.
What can I do to maintain a cetrtain depth with no speed.

[TarJak]

Just like in real life this is something that is extremely difficult. Assuming you use GWX the bouancy model is designed to model this diffuculty and therefore what you are trying to do is impossible.

[kranz]

TarJak is right.But this was possible when on periscope depth-read Das Boot pls.However the game probably doesn't give this opportunity.

[joho]

Just like in real life this is something that is extremely difficult. Assuming you use GWX the bouancy model is designed to model this diffuculty and therefore what you are trying to do is impossible.

But i must have been possible to adjust. If the boat is acending , increase weight, decending decrease or. I dont need the uboat to maintain an exact depth. But I wanna be able to adjust when its going one way or the other.

[Otto Von Strunf]

when u are abowe cca 200m and u stop your engines pres D, when u start decending pres A, then D again etc, etc... When you are below cca 200 m, use combination of A and S, but if you are too deep (220 - 240) you will need to use balasts. you can do it maximun 3 times, blow your balast and when you reach 180 press A, then u will start to decende again on 240 do it again.:up: :down: :up: :down:

[TarJak]

Or you can just set the depth you want to move to using the depth guage. In reading your first post I assumed you wanted to stay at a set depth. The boat will slowly rise or fall without the engines running in a simulation of the air ballast tanks. How fast you move up will depend on whether you blow your tanks or not. Diving without power is harder due to the GWX setting of slightly positive bouancy.

[Subject]

Or - you go get the "Neutral boyancy mod for GWX" to get rid of that modelling.

Some like to play that the crew is there to handle the boat and obey orders :roll:

[melnibonian]

If I remember correctly in the new version of GWX the reduced positive buoyancy will be default. Until then just use the optional "Reduced Buoyancy Mod".

[seafarer]

Or - you go get the "Neutral boyancy mod for GWX" to get rid of that modelling.

Some like to play that the crew is there to handle the boat and obey orders :roll:

If reality is your desired goal in the game though, even the best crew could not keep a boat at constant depth without forward momentum and use of the control surfaces (planes). A submarine in a state of neutral bouyancy is a delicate balancing act and practically impossible to acheive with mechanical means. Sure, you can pump water in and out of tanks, shift water between trim tanks and such, but true neutral bouyancy is a knife's edge state that you will keep slipping off of.

The boat, for one thing, is not stationary. It is subject to currents. Those currents will move it through water with subtly varying temperatures/salinity, hence subtly varying density. As it sinks, it's hull compresses, so it's volume changes slightly, so ballast needs to be released. So, true neutral bouyancy is fine in theory, but impossible with real life machinery.

Plus, pumping out water at depth takes a lot of power, as you have to pump out against the external pressure. It's also thus difficult to percisely meter pumping out very small amounts of water to maintain neutral bouyancy and level trim.

It's one of those classic instances where the theory is relatively straightforward, but engineering a 1000+ ton machine that can exactly implement the theory is the challenge.

[Chock]

Unfortunately, SH and pretty much every other sub sim is not totally realistic in this area, as it would probably require a supercomputer running all sorts of chaos algorithms to model it at least well, if not truly realistically. So the reduced buoyancy in the sim is about the best simple comprimise.

As seafarer notes, if you ever bring a boat to a halt out on the open ocean in real life, the amount of drift you get on currents is absolutely frightening, and you can quite easily drift a mile or more in ten minutes near estuary outflows, which extend fo many miles. So in theory your sub shouldn't even be able to remain laterally stationary either, as it would require thrusters to pull that off. And that drift would put you in water with altering densities, as the temperature, salinity, etc fluctuated.

Real U-Boats, and modern subs for that matter, will drive dynamically to the depth they want, and then try to maintain that depth by altering trim, but some fluid movement over the planes is the simpler and more desirable method, and the problem gets even worse if you launch a torpedo and suddenly lose all the weight of it as it leaves your sub, subs being equipped with compensating tanks which flood to aleviate the problem a little.

This is why most WW2 subs would perform a daily 'trim dive', to give the chief an idea of what was a likely setting required for maintaining position at various depths given the sub's altered weight from food consumed, oil and lubricants used, ammo spent etc, all of these changes alter the calculation. Even the sub itself gets smaller as it dives deep and is compressed by the water pressure!

I was reading the other day that when the Pittsburgh was launching Tomahawk cruise missiles in the Gulf War, even though in theory it can launch them in a matter of minutes, the skipper actually started the countdown to launch twelve hours beforehand, and elected to slowly approach the launch point from the start of that countdown, so that he would be able to ensure he was at the correct point and depth at the right time, and that's a modern nuclear sub with computers assisting the trim calculations!

So if it's a bit tricky to maintain depth in the sim, that's definitely realistic, even if it is simplified.

:D Chock

[Subject]

You do not need speed to dive to 180 meters. Maintaining depth do require constant monitoring and a lot of work, but that's why your boat is full of men :roll:
Please don't spread myths.

[floundericiousWA]

Perhaps your easiest way to quietly maintain a depth is to set your speed at an extremely low number (click between 0 and 1)...that will maintain some positive pressure over the surfaces and mean you're doing less sea anchor duty!

[Peto]

Historically :shifty:: "Hovering" was very difficult for the simple reason that the ocean is dynamic--varying temps/salinity/currents which impact the effort. To do it, it was typically nessecary to pump water aft, forward, here, there etc, which made noise--something that a hunted submarine was trying to avoid. Not to mention that a submarine having a dc go off while it has no momentum was a recipe for disaster as it could leave you galloping for the surface or the ocean floor. That would require HUGE amounts of noise to compensate/get the boat under control again.

A skipper might order for all stop but he was still counting on forward momentum to be sufficient for the planemen to keep the boat under control. I've never read any account of a submarine attempting to hover in a combat situation...

My 2 cents (but probably worth much less ;)).

Peto

[seafarer]

You do not need speed to dive to 180 meters. Maintaining depth do require constant monitoring and a lot of work, but that's why your boat is full of men :roll:
Please don't spread myths.

What myths? Lots of web sites by ex-submariners talk about the fact that true neutral buoyancy is impossible to acheive in a submarine. Practically speaking, the machinery, no matter how masterfully manned and handled, is not capable of such refined control of ballast and trim.

I've done a number of dives in small, 3-man deep diving submersibles. With state of the art, solid-state electronic controlled trim and ballast pumps, it was never possible to acheive and maintain true neutral buoyancy for more then brief periods of time. The Alvin pilots are some of the best trained submersible operators you'll find anywhere in the world, but no amount of artful control inputs from them could acheive precise depth maintenance for anything more then a few minutes without the use of the thrusters. And this in a vessel that only displaced a few tons, not thousands of tons.

The environment is the issue, and the environement is not stable, so you are in effect chasing a constantly moving target. For a submarine, at war, and with finite power reserves, that chase is costly - in terms of power, a ridiculous strain on the crew who must ultra-micro-manage a maze of buoyancy controls, and it makes noise running pumps and such.

As mentioned, much better off just slipping along at 1 knot or so, and let the dive planes do what they are intended for - depth and trim control.

A quote from a US Naval Officer and an engineer who served on the USS Loggerhead (SS-374, a Balao class boat) in WWII:

Lt. HARRISON W. SIGWORTH

Modern United States Submarines

In Engineering and Science Monthly (California Institute of Technology), Volume 9:8, August 1946
...<snipped the first portion of article>
...
SUBMERGED OPERATION
The achievement of neutral buoyancy is a practical
impossibility. It can be approached by pumping
water out of the trimming tanks or flooding in; but
true neutral buoyancy in which the boat will stay anywhere
it is placed below the surface without sinking
or broaching is impossible. Depth can be maintained
within a foot for hours at a time, however, by propelling
the boat through the water and using the
diving planes. These are horizontal, tiltable, planing
surfaces olaced at the bow and stern to control dewth
and ang-l e of the boat.
... <article continues>

the whole paper is here (http://calteches.library.caltech.edu/118/02/ES9.8.1946.pdf)

[PapaG39]

Man, you guys have brought up a whole bunch of interesting sea stuff to this old army guy.

Heck, I didn't know what the "Reduced Buoyancy Mod" was actually for.

Other things I am aware of such as, water temperatures, salinity and currents but I never even thought of them in this game.

You can only put so much into a $50 CD.

I was reading on some sub background material which stated that at the beginning of WWII the men who went into the German sub service had ***five years*** of training prior to entering the submarine.

When these guys went to sea they knew their boat backwards & forwards.

We pickup a shiney CD with a cool picture on it & plop it into a computer & try to make some sense out if it...

[jmr]

I recall reading in Blind Man's Bluff that there was one nuke skipper who would shut off the pumps and use "ballast parties" of sending men forward and aft to keep his boat steady.

[Jimbuna]

The Reduced Buoyancy Mod when activated will be pretty close to neutral.....when it's ready ;)

[Chock]

I was reading on some sub background material which stated that at the beginning of WWII the men who went into the German sub service had ***five years*** of training prior to entering the submarine.

Yup, the original guys in the German subs were vastly experienced sailors in many cases. When the Kriegsmarine training barque Niobe capsised in a storm in 1932 (with the loss of seventy trainee officers) Admiral Erich Raeder put out a request to the major shipping lines for experienced men, and he got some good guys, among these were Gunther Prien and Heinrich Bleichdrodt!

And the officer training was tough too, it consisted of two days physical fitness testing (with a 25 percent failure rate), followed by five months basic training for successful candidates at Danholm. Then, four months sailing training on a three-masted barque. After that, you got the formal rank of Seekadet at which point you were posted to (typically) a cruiser, and stayed with it on what was usually a trip around the world, this lasted up to nine months. Then you went to Murwick for seven more months' training, at which point you'd get the rank of Fahnrich zur See (midshipman).

Everything up to this point was standard training for every officer, regardless of whether they were going to be on a sub or not. At this point if you were a prospective line officer, you got several months weapon training, then you'd be assigned to a warship for yet another stint of six months, after which, if you did okay, you'd get promoted to Oberfahnrich. Then, you'd serve in that role for up to three years, after which, a vote by your peers would see you promoted to Leutnant zur See.

Anyone who wanted an engineering role, such as a chief, took extra exams at Murwick, which if passed, led to about five months of workshop training, followed by another six month stint on a warship, and after that, if you did alright, you'd be promoted to Leutnant (Ing). But if you wanted to be on a sub as an officer, you'd also have a further 12 week training course with classroom theory and exercises of a practical nature too. And you had to get 15 successful practice attacks in before you were allowed to progress to the next stage, which would be a stint on a U-Boat in a learning role under an experienced commander, followed by a posting to a training flotilla for even more schooling and practice.

If you made it through all that, and were lucky enough to get a new boat, you'd assemble with your prospective crew before the boat was built, this lasting up to 3 months. This was so you literally knew your boat inside out, as you got to see how it was put together. When the boat was nearing completion, any experienced officers or crew you were going to get would join you. Then you'd have three weeks of acceptance trials, followed by one of the toughest tests of all, at the Technical Group for Front U-Boats. This was an extremely realistic exercise where a highly experienced commander would accompany the fledgling captain and 'put him through the mill'. It was dreaded by candidates and many boats were actually lost in this test, at it was extremely tough and realistic. If you passed, your boat was declared ready for the front, and was refitted, during which you might get some leave, then it was off to Kiel, on with the torpedoes, and off you went to active service.

NCO's training was no less tough either, with a typical NCO on a U-Boat having to have at least three years on U-Boats, and this was on top of the selection for the ordinary seamen on the boat, which was also tough in the extreme, with a high rejection rate and no shortage of volunteers for most of the period right up until the end of WW2.

And we get a paper manual, less than 100 pages long:rotfl:

:D Chock

[PavelKirilovich]

It seems to me that most of the annoyance with regards to GWX is that it overcompensates for the initial lack of detailed seamanship in SH3.

So what we get is the player (Kaleun) being forced to act as CE, planesmen, and diving PO.
Obviously some players prefer that the AI filling their roles actually do their job.
Some enjoy the seafaring aspect.

My suggestion would be for the coding to be altered to simulate the crew doing their best to keep the boat at the ordered depth, +/- ~10-20m or so if a drastic change is what's desired. Alternatively the reduced positive bouyancy mod and suspension of disbelief simulates such action with a highly skilled crew who don't mind the ultra micromanagement of the boat.

Here's something we see in Das Boot, even. The off duty crew being displaced forwards when a crash dive is ordered to "weight" the bow further and speed the dive rate. That's another example of how SH3 doesn't really model the sailing aspects of a naval simulation. Fortunately for us it does model the combat aspects. I didn't install "MicroSoft Sailboat v3.0" here when I ran the SH3 DVD-ROM for the first time.

[TarJak]

On the contrary Pavel, SHIII does model crew weight distribution. Here's a couple of simple tests you can try for yourself;

Start off in calm weather, set depth to 7-8m decks awash with all your crew manning the aft most compartments. Set speed ahead slow. Check the attidude of the sub with the external cameral and have a look at the bow waves that are coming over the bow. Then move all your men as far forward as they can fit and repeat the view. The main thing you will notice is that your bow waves create much less splash than when your men are in the aft compartments.

I have used this technique when making night surface approaches for the past year with some success. I've also tested the spotting distances and there is a slight advantage to having your crew forward when running decks awash.

The second test is with crash diving. Save a game at a point again so the repeat can start in exactly the same conditions. Move all your crew aft and then order a crash dive timing how long it takes to get to 60m. Exit, load the save and repeat with all the crew in the forward compartments. I've recorded up to 2 seconds improvement in CD times with the crew forward over the crew aft. Usually the difference is between 1 to 1.5 secs but always better. Same result when surfacing. Angle of attack is altered by moving the crew forward or aft so you can surface at a steeper angle if the crew are aft than if they are forward.

Damage and flooding can also affect these results so it is best done with a fresh undamaged sub.

OK you can't get the crew to do stuff of their own volition, but as I understand it, that would require changes to the source code to make the crew move between compartments as part of an order to dive or surface. Unfortunately that's not likely to happen anytime soon.

[Subnuts]

Take a look at the plans on this website:

http://www.uboatarchive.net/U-570DesignBook.htm

Specifically, Plates 6, 7, 11, 12, 16, and 17. Considering the complexity of the compressed air, trimming, compensating, and ballast systems onboard a submarine of even that era, it's pretty hard to imagine even the most elite U-boat crew achieving perfect trim at full stop.

Oh, and the numbers of valves, manifolds, air lines, etc. in the control room is frankly nightmarish! :doh: