Heavy seas and rolling motion

[mike_espo]

I noticed in SH 3 how a u boat would toss and roll in heavy seas while submerged, even at depths of 200+ ft or so. However, in SH 4, a gale can be raging overhead and the boat is rock steady at periscope depth or about 50 feet or so. :hmmm:

It seems that SH3 was more realistic in this regard.

Is there a way to edit this somehow?

thanks

[rditto48801]

Waves are on the surface, a dived sub is 'below' the waves.
Why would a sub 'under' the waves be affected by them?


After doing a little googling, I found an FAQ page (apparently from the Royal Navy, relating to nuclear subs), but it seems to fit the subject at hand.
http://www.royalnavy.mod.uk/operations-and-support/submarine-service/submarine-faqs/more-submarine-faqs/*/changeNav/00h001003007001/outputFormat/print/
(near the bottom)

Q. Can you feel the waves on a submarine?
It depends on the size of the waves on the surface. During normal weather conditions, a submerged submarine will not rock with the motion of the sea. In fact, during moderate storms the submarine remains level at its submerged depth while the waves crash above. In extremely violent storms, like hurricanes or cyclones, wave motion can reach to a depth of 400 feet; though not as violent as the surface, these waves can cause a submarine to roll 5 to 10 degrees either way.Overall, it seems SH4 is more accurate in how surface conditions affect a submerged submarine.
I think even SH1 reflected this sort of effect, of being able to dive a little ways (or a bit deeper in very heavy seas) so surface conditions did not affect a sub's speed. I recall some times finding it better to just dive and go submerged at minimal speed rather than wasting fuel on the surface with barely reaching 1/3 or 1/2 of the usual speed.

[Webster]

open the subs sim file and adjust the gc_height which is the center of gravity.

that will help you get more roll

[mike_espo]

Waves are on the surface, a dived sub is 'below' the waves.
Why would a sub 'under' the waves be affected by them?


After doing a little googling, I found an FAQ page (apparently from the Royal Navy, relating to nuclear subs), but it seems to fit the subject at hand.
http://www.royalnavy.mod.uk/operations-and-support/submarine-service/submarine-faqs/more-submarine-faqs/*/changeNav/00h001003007001/outputFormat/print/
(near the bottom)

Overall, it seems SH4 is more accurate in how surface conditions affect a submerged submarine.
I think even SH1 reflected this sort of effect, of being able to dive a little ways (or a bit deeper in very heavy seas) so surface conditions did not affect a sub's speed. I recall some times finding it better to just dive and go submerged at minimal speed rather than wasting fuel on the surface with barely reaching 1/3 or 1/2 of the usual speed.

Sorry to disagree. :timeout: I refer you to the probably unfortunately out of print classic: The Boat By Lothar Gunther Buckheim.

During the Storm chapter, which was quite long, he states that the "old man" would dive the boat to give the crew a break-and he says that over 200 feet would be needed to stop the rolling/rocking motion from the angry seas above.

[mike_espo]

open the subs sim file and adjust the gc_height which is the center of gravity.

that will help you get more roll

Sorry Webster. That only appears to work when surfaced....:(

Oh well. not too big a deal. Is nice though when your in a storm. Nice thing to do for the crew.

[Stealhead]

Maybe in a huge storm youd need to go over 200ft to not feel much roll but i have read that most of the time about 100ft or so under a sub wont get much effect at all from surface condtions. makes since as as you get deeper water pressure goes up and that would resist movement at laest from the surface. That had to be a very huge strom and what would be considered normal would not apply to the story that mike mentioned. And I am not saying there would be no movement under water just no where near the amount that the boat would get on the surface. Pretty much US sailors just toughed out very rough weather only when it was considered too dangerous or the motion become a fatigue factor on the crew would they dive to avoid the roughness. In Take Her Deep the author mentions that while in a wolf pack they hit rough seas and a sailor on watch on another sub got killed when a wave smashed his binocs into his cheast so hard it crushed his diaphram and he died hours later from the pain and inabilty to breath properly.(not like they could have done anything to save his life)

[rditto48801]

Sorry to disagree. :timeout: I refer you to the probably unfortunately out of print classic: The Boat By Lothar Gunther Buckheim.

During the Storm chapter, which was quite long, he states that the "old man" would dive the boat to give the crew a break-and he says that over 200 feet would be needed to stop the rolling/rocking motion from the angry seas above.

And I again point out what I had found online. Mainly this part
"In fact, during moderate storms the submarine remains level at its submerged depth while the waves crash above. In extremely violent storms, like hurricanes or cyclones, wave motion can reach to a depth of 400 feet; though not as violent as the surface, these waves can cause a submarine to roll 5 to 10 degrees either way."

To me hat is an indication that, unless weather gets really bad, it won't do much to a submerged sub, but that if weather gets really bad, a sub can still feel the effects to some degree when submerged, even if down a few hundred feet.
I am unsure if I have ever encountered a storm 'that bad' in SH4.

I think I have encountered that kind of weather in SH3... several times... waves so big the diesels die and you occasionally get waves tossing the sub up and down, occasionally a wave going up and over the conning tower as the sub is on a downward motion... It annoyed me that my crew can gleefully be on watch during those conditions, it seems like it would make sense in SH3 if they would come inside when constantly getting hit with waves that should technically sweep everyone off the conning tower... not like aircraft could fly (or even spot anything smaller than small to mid sized merchant/war ship) in such conditions anyways...
It was during such weather I noticed the sub seeming to have a mild 'roll' when even deep underwater.
But the again, isn't the English Channel known for heavy seas that can get so bad they sink ships?

[AKULA_71]

I know from personal experience a 688 SSN rolled quite alot @150ft depth when hurricane Bob was topside in Long Island Sound (1991). A lighter gato boat getting bounced around slightly while submerged deep in heavy seas isn't surpriseing at all.


In SH3 this was modled kinda close, even at 70m depth a type VII will move around slightly in heavy seas. On the other hand, in SH4 once under 60ft depth all hell could be breaking loose topside and one couldn't really tell in control.

[PortsmouthProwler]

FACT: You could be in a rowboat 2,000 miles out at sea in the Pacific, and if a tsunami were travelling right through your location, you'd never know it - the 'wave' would be about six inches, tops.

Check out some basic physics. A wave in a medium such as water is highly misunderstood by most people. The compression and rarefaction of the particles (i. e., water molecules, in this case - also bear in mind that water is an incompressible fluid) is almost entirely imperceptible out at sea (and I mean well out at sea). The breakers and what most people think of as waves occur only when the bottom of the wave starts to hit a substance even more incompressible, i. e., land.

Das Boot is a work of fiction. As a Lit major, I'm all for poetic license, but recognize it for what it is.

* German boats were smaller than US fleet boats. A smaller vessel will be more affected by sea state.

* Where you are is crucial. I respect the opinion of a sub vet, but notice where the boat was - in Long Island Sound in a hurricane. Shallow and enclosed; even a modern 350' long behemoth with the tonnage of a WWII CV is going to roll at a shallow depth.

In general, submarines do not roll, pitch, or yaw greatly under 100'. Furthermore, as far as SH3 and SH4 go - a great deal of the action in 4 occurs in 'blue water', away from a continental shelf. A lot of the action in 3 is above a continental shelf. This is a significant difference in what you can expect for sea state and weather, so maybe the devs have modelled it much more reralistically than one might think.

[Rockin Robbins]

Actually it would be partially a function of the height of of the submarine. What's periscope depth on that 688 SSN? I'll bet it's a lot taller than the fleet boat. The mechanical advantage difference set up over the longer distance between keel and top of the sail might make the 688 actually move more at the same depth than a fleet boat would. And the greater area of the sail, plus the round cross section of the body giving the boat little inherent roll stability would accentuate the motion.

I'll bet the modern boats have more but gentler motion, while the fleet boats would have a shorter but snappier motion in a big storm at 200'. It would be interesting to know from someone who has experienced both.

[rditto48801]

Actually it would be partially a function of the height of of the submarine. What's periscope depth on that 688 SSN? I'll bet it's a lot taller than the fleet boat. The mechanical advantage difference set up over the longer distance between keel and top of the sail might make the 688 actually move more at the same depth than a fleet boat would. And the greater area of the sail, plus the round cross section of the body giving the boat little inherent roll stability would accentuate the motion.

I'll bet the modern boats have more but gentler motion, while the fleet boats would have a shorter but snappier motion in a big storm at 200'. It would be interesting to know from someone who has experienced both.

There are a few pics on Wikipedia, one of which is supposed to be the sub at periscope depth (upper right of page), plus two other pics.
http://en.wikipedia.org/wiki/Los_Angeles_class_submarine
Not much, but it's better than nothing.

And a site I like, FAS.
http://www.fas.org/programs/ssp/man/uswpns/navy/submarines/ssn688_la.html
Got a few nice pics at the bottom, some which link to a gallery.
http://www.fas.org/man//dod-101/sys/ship/ssn-688_i.htm

*drools over gif of sub breaching surface fast*

[mike_espo]

FACT: You could be in a rowboat 2,000 miles out at sea in the Pacific, and if a tsunami were travelling right through your location, you'd never know it - the 'wave' would be about six inches, tops.

Check out some basic physics. A wave in a medium such as water is highly misunderstood by most people. The compression and rarefaction of the particles (i. e., water molecules, in this case - also bear in mind that water is an incompressible fluid) is almost entirely imperceptible out at sea (and I mean well out at sea). The breakers and what most people think of as waves occur only when the bottom of the wave starts to hit a substance even more incompressible, i. e., land.

Das Boot is a work of fiction. As a Lit major, I'm all for poetic license, but recognize it for what it is.

* German boats were smaller than US fleet boats. A smaller vessel will be more affected by sea state.

* Where you are is crucial. I respect the opinion of a sub vet, but notice where the boat was - in Long Island Sound in a hurricane. Shallow and enclosed; even a modern 350' long behemoth with the tonnage of a WWII CV is going to roll at a shallow depth.

In general, submarines do not roll, pitch, or yaw greatly under 100'. Furthermore, as far as SH3 and SH4 go - a great deal of the action in 4 occurs in 'blue water', away from a continental shelf. A lot of the action in 3 is above a continental shelf. This is a significant difference in what you can expect for sea state and weather, so maybe the devs have modelled it much more reralistically than one might think.

I happen to have a physics degree. Tsunami effects are a totally different effect than ocean waves. It has nothing to do with compressability of fluids.:rotfl: It does have everything to do with wave propogation, magnitude of the wave and relative depth where the tsunami wave is at the time.

These are two unrelated phenomena.

Before you flame a post, check your facts.

[rditto48801]

wait, a tsunami?
It skipped my mind earlier that tsunami is the word for giant waves that only are 'visible' close to shore.

Also, aren't tsunamis caused by tremors/quakes on the ocean floor (or islands or on shore), and not by wind/storm activity?

Storms are like splashing in water a lot while tsunami's just being more of a single big 'ripple', right?
(okay, bad description and comparison... but sort of gets the point across)

I would hate to be in a sub near shore when one showed up...
try to explain to high command why they are going to need landing ships and cranes, and not a tug, to recover the sub... :doh:

[PortsmouthProwler]

I happen to have a physics degree. Tsunami effects are a totally different effect than ocean waves. It has nothing to do with compressability of fluids.:rotfl: It does have everything to do with wave propogation, magnitude of the wave and relative depth where the tsunami wave is at the time.

These are two unrelated phenomena.

Before you flame a post, check your facts.

There's no need to fly off the handle, sir, I wasn't flaming anyone, as you may have observed from the lack of a quote.

If you want to go much further into a physics lecture, go to another forum here, I'm sure this isn't the right one for it. The point I was making was that the depth of the water, and to some degree the presence or absence of dry land near you, are the chief criteria. I was mentioning compressibility of fluids to make it clear that waves in water, for instance, behave a little differently from other waves that some readers may have had in mind. The infelicitous expression arose from my inability to recall proper terminology.

Incidentally, if I recall my physics classes, a wave in water is a wave water is a wave in water. A tsunami's height from the very bottom to the top may be immensly greater than waves caused by meteorological sources, but it's still a wave. As you might have noticed, all I was really trying to point out is that waves, regardless of height (total height for those still reading, i. e., the amplitude) are not going to affect a submarine very much until the bottom of the wave hits land, because a submerged vessel is inside the medium.

And no, this is not the right place to conduct a physics class, if I'm mistaken still. For those of us poor benighted souls who didn't major in physics, you might have some consideration that we might be recalling something from quite a while ago and refrain from your supercilious tone and superfluous and unamusing smilies.

I'm a professional writer, BTW - I could spend all my time, every day, on Internet forums correcting people's English, spelling, etc. I don't because it would be rude. Sometimes, sir, it doesn't matter if you're right, if all you do is annoy the listener.

[Sailor Steve]

I don't know a thing about tsunamis, but at sea the wind causes extreme wave buildup. I've been at sea in a moderate storm, and when the bow of your ship plows under the water and the wave hits mount 51, and the resulting splash goes over your head while you're standing on the signal bridge, you know it's more than just a few inches.

Here is the expected wave height at different wind speeds:
http://www.peardrop.co.uk/beaufort.htm

Note the maximum listed in a hurricane - 16 meters. That's more than 50 feet.

As for the submerged sub being affected, again I don't know about being extremely deep, but I've read that at periscope depth conditions aren't much better than on the surface in a storm, and you need to be at least 100 feet down to start being comfortable.

[PortsmouthProwler]

Yes, you're right, that's the whole point. A surface vessel rides on top of the wave and gets bounced around. A sub can go below the disturbance; even in a wave of great amplitude, once the sub is well submerged, it's not subject to the same 'roiling' as a surface vessel is.

I grew up on the New England coast and am far from an experienced mariner, but I have been out at sea daily (usually no more than 35 - 50 miles) and know what you're saying. Incidentally, I worked at Portsmouth Naval Shipyard for a while and was on the boats every day while they were overhauled. Some of my more 'lubberly' colleagues would ask some of the submariners about this very point. Most often, they stated they would rather be in the sub and safe below, than on top, in a storm.

[Rosencrantz]

Few notes:

1) If you are using SHIII Commander, you can alter the wave height and get really huge ones. Then it's best to think wind speed be maybe one and half or two times that your OOD tells you.
2) Once I tried to take a look at DD in 5 m/s (10 knt) wind while I was at PD with II-class small boat. Using stadimeter was almost impossible because the pitching and rolling of the boat. I didn't find it very realistic, even if the boat was small, and I think IV has made good progress in that.
At the same time I found also that when looking trough the scope, it didn't look like the waves would run over the scope, as they should. Again I think "One-Four" is doing better.
3) Just couple weeks ago I was reading a fleet boat's War Patrol Report and found they had to take her down to 120 ft in the gale to find a steady water. Saddly I don't remember which boat that was.
4) It's true waves will get more height close to the shore, as the sea bottom gets closer to the surface. However, SHIV is not able to model this and I'm very pleased my processor capacity is not wasted even to try this kind of a task.
5) It might be also true that fleet boats in the IV are a bit too steady while at PD under 30 knt near gale winds. However, if you like pitching and rolling, just take the boat on the surface. Even 10 knt wind is enough to get your boat pitch and roll like a canoo.
6) For the PC sim, it's hard to be realistic enough.


Greetings,
-RC-

[ahclem]

I'm having the opposite problem. Something has glitched in the game and now when my sub is on the surface with smooth seas it is rolling excessively. I'm talking about 30 degree rolls with the crew standing perfectly perpendicular to the deck. It looks really weird, but it's enough to give one DIMS if you stay on the bridge.

Someone mentioned changing the CG. How exactly does one do that?

[vanjast]

wait, a tsunami?
It skipped my mind earlier that tsunami is the word for giant waves that only are 'visible' close to shore.

Also, aren't tsunamis caused by tremors/quakes on the ocean floor (or islands or on shore), and not by wind/storm activity?

A Wave is energy, either transferred to the sea via wind, or earthquakes.
A tsunami's wave energy is Longitudinal - in the direction of travel, hence it literally has no vertical wave component. When it gets to shallow water, this impulse(s) of energy have nowhere to go except vertical, making very large waves.

Wind storm waves are Transverse waves at 90 degrees (vertical) to the direction of travel. As the waves pass over you (sub) you feel the changes in pressure energy, which causes the rolling depending on your course-vs-wave direction. The deeper you are lessens the pressure variations, thus the rolling effects.

a simple (http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/Physics/wavepropagation.htm) explanation of wave types
:)