maintaining depth at stop

[PurpleCity]

My understanding is that submarines cannot maintain depth and will surface if engines are off. If I remember correctly, SHIII modeled this.

Is there a mod that simulates this behavior for SHIV or is this hardcoded in the game engine?

I'm also looking for 2 other mods with no luck
- is there a way to disable/hide/mask the hull damage indicator?
- is there a way to disable/hide those pesky icons in SHIV?

[AVGWarhawk]

True, a submarine must maintain some forward motion to sustain depth. Some say the sub will rise and others say it will sink if there is no forward motion. That argument went on for sometime in SH3. At any rate, I believe this is hardcoded in SH4 and can not be addressed. There was some discussion at the RFB forums about this and I believe determined that this can not be modeled in SH4.

I do not have the answer for your last two.

[tater]

Real subs didn't automatically broach if stopped. It was trim dependent, but trim varis from moment to moment, someone walks from one part to another of the sub, the water temp changes, etc, ad naseum. Unfortunately, the two solutions to hack this behavior into SH3 don't seem to work in SH4 (making the sub slowly surface all the time without down-planing, or having it slowly sinking without up-planing).

The simple solution for the gamer is to not stop the sub, or only rarely and for a very short time period, and never shoot while stopped. Easy enough to not cheat, really :)

[Rockin Robbins]

There was an interesting exception to the rule that a sub had a lot of trouble maintaining depth at all stop. If the thermocline was enough different in temperature, there was a layer of dense cold water below a less dense layer of warm water. A submarine could set ballast to sink in the warm layer but still have enough positive buoyancy in the cold layer to sit there for a couple of days without power if they wanted to. A couple of times during the war that saved the subs' cookies, giving them the opportunity to shut everything down and affect repairs without worrying about depth-keeping or running out of battery power.

[Webster]

we all know subs pump water in or out to control depth

so think about it, if you were the skipper and you life depended on stealth, would you rather have negative boyancy so your sub sinks at all stop or positive boyancy so your ship will rise at all stop and get your head blown off.

positive or negative boyancy is not designed in, it is a setting chosen by the captain. plus if you want to dive faster like all subs do, then positive boyancy is going to be fighting you as you try to dive.

IMO all subs made sure they were at some level of negative boyancy any time they werent surfaced

[Blood_splat]

What about firing torpedoes, would they have to adjust the trim to compensate before firing?

[Soundman]

we all know subs pump water in or out to control depth

so think about it, if you were the skipper and you life depended on stealth, would you rather have negative boyancy so your sub sinks at all stop or positive boyancy so your ship will rise at all stop and get your head blown off.

positive or negative boyancy is not designed in, it is a setting chosen by the captain. plus if you want to dive faster like all subs do, then positive boyancy is going to be fighting you as you try to dive.

IMO all subs made sure they were at some level of negative boyancy any time they werent surfaced

I completely see your point, but on the other hand, if something goes badly wrong, I wouldn't want to sink to crush depth either.

[scott613]

Don't know much about WWII subs - but - in modern subs - it was relatively easy to maintain depth without forward motion... The DOW and COW had to pay attention though... The newer subs even handle hovering automatically... Then there was always the infamous "TRIM PARTY" to indoctrinate a new officer into the wonderful world of depth control...

[SteamWake]

A common misconception.... "Hover" does not indicat a full stop, more rather a few (1-3) knots, just enough to keep some flow over the planes to maintain depth and attitude yet not disrupt the launch of the unthinkable.

[Rockin Robbins]

Scott, were you ever in a sub that floated on top of the layer? That sounds like it would be pretty amazing to do.

[Rockin Robbins]

IMO all subs made sure they were at some level of negative boyancy any time they werent surfaced

Webster, not to be offensive or anything, but we're not talking about opinion. We are talking about actual practice as verified by the people who actually ran the submarines.

In actual practice there was a tank called the negative buoyancy tank. Once per day the submarine took a "trim dive." Sub jockeys, check my accuracy here and keep me straight. In the trim dive, you dive the sub, slow it way down and with fore and aft trim tanks you level the boat. Somewhat simultaneously you fill or pump negative until the boat is at perfect negative buoyancy. The tank (in WWII anyway) is then marked at the level of neutral buoyancy. Fore and aft trim tanks are calibrated to know how bow or stern heavy the boat is. When a torpedo is fired, ballast equivalent to the weight of the torpedo being fired must be immediately added to the fore or aft trim tank to compensate for the lost weight and still leave the boat in balance.

Part of the diving procedure was to flood negative to the mark. Yes, you remember that, I see. :|\\ "The mark" would be that neutral buoyancy level established in the trim dive earlier in the day. That way, subject to any changes to conditions since the trim dive, the boat dove adjusted as closely as possible to neutral buoyancy.

Now I will speculate just like you :rotfl:, making an educated guess based on many books I have read by World War II submariners. If a submariner did something that departed from "the book," that would have been remarkable and noted in any of the books I have read. None of them have mentioned flooding negative to a level above the mark.

To me, that means that this part of the procedure was one that maybe was not required, but was one that captains were very reluctant to depart from, just like maintaining under a 10º dive angle, even though after the war the guppies successfully used dive angles that were much greater and speeded dive and surfacing times. Nonetheless, in spite of possible gains from changing the practice, during the war, captains were very precise about adhering to the official guidelines for diving and surfacing procedure.

[tater]

RR, I don't know much about the guppies, but might it be fair to say the slower dive times in fleet boats were doctrinal, rather than hardware limited? Ie: they could go down faster had they put more than 10 degrees on the planes?

[Rockin Robbins]

Yeah, you can say that again! Read Gallant Lady: A Biography of USS Archerfish for a FULL rundown on that. Matter of fact, that's EVERYBODY's reading assignment to read a book that's altogether too much fun to hold all that information. Their job was to find the real limits of the design and they did it to the point of hurting people because of the steep angles. They were among the first to really violate the guidelines, which were not orders, but were treated that way during the war.

Put yourself in the place of a sub captain. You choose to dive at 25º (which turned out from Archerfish's tests to be perfectly reasonable) but something unrelated went wrong and you lose some crewmembers. It's inquest time and they start asking questions. "Did you exceed the guideline of a 10º down bubble on the dive?" If you answer "Yes" the inquest is over and they have their scapegoat. Bend over. I see military people smiling and shaking their heads to that one.:rotfl:

[tater]

How did that change the crash dive speed?

[Bilge_Rat]

things can go wrong very quickly in a sub:

http://www.usschopper.com/Chopper%20Deep%20Dive%20Report.htm

part of the reason why sub skippers would not do a quick deep angle dive unless there was a compelling reason.


On the other point, ww2 subs were generally trimmed with a slight negative buoyancy and would use the planes and the forward motion to maintain depth. I don't remember all the reasons, but one is the fact that forward motion tends to impart positive buoyancy on its own due the water resistance/pressure which would cause the sub to rise. I think this is similar to the airlift principle with an airplane's wings. In practice, I understand it was also easier to maintain depth in this way rather than with a neutral or positive buoyancy.

[Webster]

IMO all subs made sure they were at some level of negative boyancy any time they werent surfaced

Webster, not to be offensive or anything, but we're not talking about opinion. We are talking about actual practice as verified by the people who actually ran the submarines.



not offended at all but not everyone is an experienced sub mariner so opinions do happen lol.

all i was trying to point out is, since it is near impossible to get absolute true neutral boyancy without some margin of error, so this "small" margin of error was IMO (theres that dirty word again) going to be on the negative boyancy side of neutral.

what they called neutral boyancy really wasnt, it was just as close as you could get within the small margin of error.

EDIT: i have reversed my position on this subject, i now believe any margin of error was on the positive boyancy side to allow survival in case of loss of power. i failed to consider this before.

[Rockin Robbins]

If your neutral buoyancy is perfect now, in 10 minutes it will no longer be. Most captains took a trim dive a day. Since they didn't plan to stop completely anyway, close was close enough.

I was at an airshow watching a different kind of submarine, the Fuji blimp, trying to get off the ground. This was a mini blimp and there was a rail around the outside of the gondola. They asked me to help them launch, so I walked over. First, they dropped ballast until we judged the blimp weighed about 20 pounds or so. The captain got on the speaker and said, "Now everyone hold the blimp as far over your head as you can. Then jump up use your whole weight to slam it into the ground!"

So about 15 of us body slammed the blimp into the ground. Turned out there was a kind of pogo stick on the bottom of the gondola that shot the blimp up in the air, the pilot gunned the engines and took off, easily generating 20 pounds of lift by forward motion and angle of attack. It all took a shorter time than it took to type this. Amazing!

[DaveyJ576]

No single post in this thread hit the mark exactly, but when combined together, this question was answered pretty well! :up:

A couple of nitpicks:

Submarines flood water in or pump it out to adjust buoyancy, not depth. Depth is controlled strictly by the planes.

Consider this: Take a submarine that is level on the surface and tilt it downward at a 25 degree angle. A submarine's point of tilt is amidships, not at the stern. What happens? The bow up to the conning tower fairwater is submerged, but the stern is sticking up into the air. What is at the stern? The propellers and the stern diving planes! It is true that you can flood the negative tank to gain negative buoyancy, but most of the dynamic force necessary to submerge a submarine is provided by propulsion, assisted by the diving planes. Stick the propellers up into the air and you have lost a great deal of that dynamic force. You would also loose nearly all the control over your angle as it is the stern planes that control the angle!

The bow planes are used to control depth and the stern planes for angle. Submariners live in fear of a casualty called a "jam dive" on the stern planes. That is a mechanical failure of the operating mechanism that causes the planes to go to full dive and stay there. This is what happened to the Chopper and is what came within a hairsbreadth of causing her loss. A submarine will go out of control faster than you can believe in this situation. It happened to me a few times and it is scary as hell.

What am I getting at? Yes, you can take a larger down angle when diving, but there is a point of diminishing return. All of the factors have to be considered. 40 second dive times for a boat as large as a Fleet Boat is pretty damn fast already. Large down angles while diving are possible to do, but are not desireable until the boat is completely submerged, and even then you have to be careful. A really fast dive time doesn't mean squat if you lose control and exceed collapse depth.

Torpedoes are neutrally buoyant. Once they are expelled, water floods the tube. The torpedo is the same weight as the water. Once the outer door is shut, the tube is drained into the Water Round Torpedo (WRT) tank. Therefore, the compensation does not change. Even still, the planesman, Auxiliaryman of the Watch (who runs the Trim and Drain manifold), and the Diving Officer have to really pay attention to buoyancy and depth control when shooting fish.

Dave

USS Darter SS-576 1984-87

www.pigboats.com (http://www.pigboats.com)

[scott613]

Oh yeah - this discussion reminds me - we had what we called the Safe Operating Envelope for the boat... What it did was effectively limit the speed of the boat at shallow and deep depths to prevent unsafe depth excursions in the event of a casualty such as a stern planes jam... An unwanted broach can be as bad - well almost as bad - as exceeding test/crush depth... We practiced the jam dive drill all the time... First action - BACK EMERGENCY...

[Rockin Robbins]

Wow, Scott! That wouldn't be good for the heart there.:eek::eek:

[aanker]

May be of interest:

From:
http://www.fleetsubmarine.com/diving.html

Submarines are designed so that, with the main ballast tanks full, the weight of water they displace will be as close as possible to exactly equal to the weight of the boat. In practice, the boat should retain a slight amount of positive buoyancy, so that it will want to slowly rise to the surface if nothing else acts to keep it under.
and
Since the boat is normally trimmed to be slightly positively buoyant, the planes are used to hold it down. This is a safety factor. If all power is lost it is normally preferable to slowly rise to the surface and not to sink. Even in wartime there is always at least a chance of surviving. If you sink all the way to the bottom in mid-ocean there is virtually a 100% certainty of dying.
Happy Hunting!

Art

[Rockin Robbins]

Ewwwwww! That's some kind of oversimplification because the trim ballast system and negative tank have to have some water in them. The boat would have to have a fair amount of reserve buoyancy with the main ballast tanks full or it couldn't carry any cargo or people. Once a tank is empty, you can't make it any lighter.

I think the statement is probably correct with full MBTs and a default amount of water in the trim and neutral buoyancy systems. Davey? What's your take?

[aanker]

Ewwwwww! That's some kind of oversimplification because the trim ballast system and negative tank have to have some water in them. The boat would have to have a fair amount of reserve buoyancy with the main ballast tanks full or it couldn't carry any cargo or people. Once a tank is empty, you can't make it any lighter.

I think the statement is probably correct with full MBTs and a default amount of water in the trim and neutral buoyancy systems. Davey? What's your take?
I should know better than to 'dance' with you again RR ..... lol - however I didn't want to quote the entire page. They go into greater detail on the website. The weight of the boat would of course include 'cargo & people'

http://www.fleetsubmarine.com/dynamics.html is also helpful.

Happy Hunting!

Art

[Webster]

we all know subs pump water in or out to control depth

so think about it, if you were the skipper and you life depended on stealth, would you rather have negative boyancy so your sub sinks at all stop or positive boyancy so your ship will rise at all stop and get your head blown off.

positive or negative boyancy is not designed in, it is a setting chosen by the captain. plus if you want to dive faster like all subs do, then positive boyancy is going to be fighting you as you try to dive.

IMO all subs made sure they were at some level of negative boyancy any time they werent surfaced

I completely see your point, but on the other hand, if something goes badly wrong, I wouldn't want to sink to crush depth either.

thats an equally good point, i was only thinking of accidentally being detected if something went wrong yet like you say to survive you dont want to sink either so being detected on the surface gives you a better chance to survive than crush depth. :up:

[DaveyJ576]

Main ballast tanks are always completely empty or completely full. Their purpose is to provide or eliminate the overriding postive buoyancy that holds the boat on the surface. The trim tanks are used to regulate the buoyancy of the boat.

While in port between patrols, a careful accounting of how much fresh water, fuel oil, lube oil, hydraulic fluid, torpedo alcohol, stores, etc., etc. is brought on board and the weight of all this is used to figure the initial compensation. One of the first things that is done after clearing the harbor outbound is to conduct a trim dive. It is not uncommon for the boat to have trouble submerging or maintaining depth at this time. As much time as is needed it taken to properly adjust the ballast compensation by flooding water into or pumping it out of the trim tanks. The goal is to obtain perfect neutral buoyancy so that a minimal use of the planes will maintain depth. The whole time the boat is at sea, a running tab is kept on consumables useage and the compensation is periodically adjusted as needed. Trim dives usually took place once a day.

In reality, on the fleet boats, perfect neutral buoyancy is virtually impossible to achieve. The manually operated trim and drain system, while a very good design, was just not sensitive enough to get to that point.

From a submariners standpoint, if you can't get to neutral buoyancy you would default to a slight positive buoyancy. Contrary to popular belief, true crash dives did not happen all that often with our boats (radar gave you enough warning). If you had to go down quickly you could flood the negative tank and you would go down like a rock. I heartily agree with the other posts that it is far better to broach (although obviously not desireable) than to sink. You at least have some chance at survival if you broach, but if you exceed crush depth you WILL die.

Dave

www.pigboats.com (http://www.pigboats.com)

[tater]

Dave,

love your posts, some of the very best I have read here. Keep educating us, this stuff is great!

tater

[Rockin Robbins]

Agreed. It's great to hear from a real submariner who knows what he's talking about.:up:

[DaveyJ576]

Thanks guys. I really appreciate it. For a real world example of the importance of proper ballasting, surf over to http://pigboats.com/dave5.html when you have a chance (insert shameless self-promotion here!) :lol:

Dave

[Dread Knot]

Thanks for the detailed description on how these beasts swim Davey. Informative site too. :up:

I wish the sim had things like trim dives, equipment malfunctions, (that aren't related to battle damage) training crewmembers, etc. There's so much more to a patrol in a sub than a leisurely cruise between ship sinkings.

[DaveyJ576]

I agree that a random equipment malfunction feature should be added. It shouldn't be too hard to do and would add an extra level of realism to the game.

Thanks for the kind words on the site. My partner Ric Hedman does all of the grunt work, I just do the writing.

Dave

[Orion2012]

Excellent read, Davey.

Goes a long way to show how dangerous even small changes could be. Only thing I can add, is, now I can say with absolute certainty I'm not the only man ever hit in the head with a toaster.

[Rockin Robbins]

I agree that a random equipment malfunction feature should be added. It shouldn't be too hard to do and would add an extra level of realism to the game.

Thanks for the kind words on the site. My partner Ric Hedman does all of the grunt work, I just do the writing.

Dave

No Kidding! That is the single most egregious omission in the game. Equipment failures were the third side in the war...you were always fighting two enemies.