Heavy seas and rolling motion

[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]

Originally Posted by 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.

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_Ang...lass_submarine
Not much, but it's better than nothing.

And a site I like, FAS.
http://www.fas.org/programs/ssp/man/...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]

Originally Posted by 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.

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...

[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]

Originally Posted by 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?

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 explanation of wave types

[PortsmouthProwler]

Originally Posted by mike_espo

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.