paging Captain Henning.....

Skip Miller

Skip Miller

Final Approach
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Skip Miller
OK, there is a good sea running but "terrible storm"? I don't think so.

Modern cruise ships are so top heavy that they usually run for port (or calm seas) whenever the sea kicks up. How this one got caught might be an interesting story.

It looks to me like the ship has a pretty good list to starboard; it seems like the rolls go much further to starboard than to port, but that could be the camera angle. How much further do you think she can roll without going over?

Can you spell (I almost typed "smell") barf?

-Skip

http://www.liveleak.com/view?i=dd0_1174965550
 
Skip Miller said:
OK, there is a good sea running but "terrible storm"? I don't think so.

Modern cruise ships are so top heavy that they usually run for port (or calm seas) whenever the sea kicks up. How this one got caught might be an interesting story.

It looks to me like the ship has a pretty good list to starboard; it seems like the rolls go much further to starboard than to port, but that could be the camera angle. How much further do you think she can roll without going over?

Can you spell (I almost typed "smell") barf?

-Skip

http://www.liveleak.com/view?i=dd0_1174965550
Click to expand...

I've been on a cruise ship in rough sea's a couple of times. Worst was Gulf of Alaska in late September 40-50 waves. Most people did not make Dinner. We had a former Oil Tanker Captain at our table. The ship rolls a little and shudders. You definitely get drunken walk.

The closer you are to the CG the weaker the effect, that's why they put the kitchen there.

The ship will roll just about 90 without flipping since most of the weight is at or below the water line, nothing but people and a lot of air above the water line. They tend to right themselves, imagine that, sort of like an airplane:yes:
 
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gprellwitz said:
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Click to expand...
Grant, it's safe for work - it's just a cruise ship listing in wind and waves, nothing else. I promise! :)

And it seems to me that there might have been a direction in which to point that sucker that it wasn't listing 60 degrees!
 
RMCN172RG said:
The ship will roll just about 90 without flipping since most of the weight is at or below the water line, nothing but people and a lot of air above the water line. They tend to right themselves, imagine that, sort of like an airplane:yes:
Click to expand...
There is a roll angle from which they will not recover, and in my limited experience it is significantly less than 90*. I don't know about cruise ships and that was an implied part of my question. I do know that the 5,000 ton cargo ship I was on in the Navy had a critical angle somewhere in the low 50* range, I forget now. When she is tender and rolling 45+* you hold your breath every time. It got so bad that this former civilian cargo vessel (a WWII vintage Victory Ship) tweaked for military cargo duty had a 100 ton pile of old railroad track welded to the lowest level in the #1 hold to improve her stability.

The key here is that the center of bouyancy CB is below the CG. With that information alone you would think that the ship would roll over. However, a ship does not roll around the CG as an axis; it rolls around the metacenter. As the ship rolls, the wetted area changes and the CB moves laterally towards the roll while the CG moves in the opposite direction. Result: the roll is stable, i.e., a rolling ship will stop rolling. Depending on the height of the CG and metacenter, the ship will either be stiff (will roll with a short duration roll) and tend to snap back to level very quickly (very uncomfortable for all aboard), or tender, rolling with a longer period and threatening at the end of each roll to not come back.

The cruise ship in the video looks pretty tender to me. She was closer to turning turtle than you think.

Wiki has some good info on stability.

-Skip

http://en.wikipedia.org/wiki/Metacentric_height
 
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Skip Miller said:
OK, there is a good sea running but "terrible storm"? I don't think so.

Modern cruise ships are so top heavy that they usually run for port (or calm seas) whenever the sea kicks up. How this one got caught might be an interesting story.

It looks to me like the ship has a pretty good list to starboard; it seems like the rolls go much further to starboard than to port, but that could be the camera angle. How much further do you think she can roll without going over?

Can you spell (I almost typed "smell") barf?

-Skip

http://www.liveleak.com/view?i=dd0_1174965550
Click to expand...

No doubt, that was a signifcant storm, force 10 at least. Notice that when a wave came out of the lee of the wave behind it, the white caps would sometimes get bown off, that takes serious wind. The depth of the roll is not as significant a factor in stability as the speed at which she returns from the roll, and from what I saw, she had a lot of reserve stability left. The reason she rolled harder one way than the other is that the wind and seas were coming off the forward quarter. If I had had sea room for it, I would have turned around and put the wind and seas 25* off my port or starboard quarter (depending on which hemisphere, stbd for northern, port for southern) and ran with it, it would have been much more comfortable for the PAX and got me out of the storm in the minimum amount of time. But I don't know his situation, he may have been making a run for port or a lee somewhere and been close. The ship was at that point, not in visibly in danger, just discomfort, although those kind of conditions can bring about troublesome issues which can change that status in a heartbeat. This is not the first, nor the last instance of a cruiseship being caught out (really, driven into) into a storm. My friend took a honeymoon cruise to Cozumel a few years ago even after I told him "Hey, you don't want to take this trip, there's a really good chance you're gonna get caught in this hurricaine." Luckily he and his bride were seasoned seafarers and had fun even though "The whole ship smelled like puke". They have bookings and a schedule to follow, and had they (the cruiseline) cancelled the sailing, it would have caused them an even greater nightmare. I've got many stories of when people insisted on going out even when I told them "Look, it's really really rough out there, you will not enjoy this, come back tommorrow when the system has blown through, we'll go then..." "I booked and paid for this trip 9 months ago, you're not going to rip me off like this...blah blah blah, yada yada...), after that, as long as I didn't think there was a concern for the safety of the vessel, we'd go, and when they'd beg to head back, "Oh no, I wouldn't consider cutting you short on any of the trip you paid for, only three hours left...":D Once we came back in and the guy was cussing and threatening to sue, the boss just said "Go for it, the security system has on tape where you argued and threatened to sue if we didn't take you out even though the captain tried for half an hour to convince you not to go." Some people are just stupid when it comes to their vacations....
 
Skip Miller said:
There is a roll angle from which they will not recover, and in my limited experience it is significantly less than 90*.
Click to expand...

Not necessarily, there are vessels designed that will, as long as the water tight integrity of the hull is retained, right themselves from any angle including executing full rolls. A cruise ship of course is not in this catagory. A cruise ship though is signifcantly different from a naval vessel in design though carrying maximum beam to nearly maximum draft for a long run of its length and having hard chines giving it good inherent initial stability and a stong lever arm as the roll progresses. The key thing we watch for in heavy weather is the time spent at maximum roll angle, if the roll reverses quickly, there is nothing to worry about, if the vessel wallows for several seconds there, it's time to be concerned regardless the degree of roll. The main factor to address in this is free surface effect of fluids in the tanks and bilges. You always keep your bilges dry and tanks either empty or full drawing off of only one fuel or water tank at a time, and having ballast tanks either pressed or empty.
 
yeah, you wouldn't want your ballast tanks all wrinkly!!! :no:

(although how that would help in this situation, *I* don't know!) :)
 
Henning said:
No doubt, that was a signifcant storm, force 10 at least. ...
Click to expand...

It says in another caption of that video that is was a cyclone.

My question is how izzit that the helicopter is so stable? There had to be a lot of wind and wind shear.
 
mikea said:
It says in another caption of that video that is was a cyclone.
Click to expand...
Whereas it certainly could have been a cyclone, at some distance from the center things aren't bad - but you are still in the cyclone.
My question is how izzit that the helicopter is so stable? There had to be a lot of wind and wind shear.
Click to expand...
That, and the good visibility on the video (no rain-filled air) was my clue that this was probably near the edge of a significant storm. Wind way down but plenty of sea.

-Skip
 
mikea said:
It says in another caption of that video that is was a cyclone.

My question is how izzit that the helicopter is so stable? There had to be a lot of wind and wind shear.
Click to expand...

Cyclonic is the type and shape of storm (as are most of that magnitude in the tropics and sub tropics where a cruise ship operates), though not an indicator of the exact wind force of any given location within the system. From the sloppyness and size of the waves, it appears that the wind force is diminishing, probably a Force 9 at that point. (Look up Beaufort Scale). My guess would be he's on that course to the seas because he needs to stay off a lee shore. The helicopter is stable because the winds are relatively constant at around 45kts and they are on the back side of the storm where things aren't that gusty and shearing.
 
I had a charter which the master insisted that we put out. Okaaaay, it's your money.... 30 minutes into a 3 hour tour he pleaded we turn back. I said, the gang is asleep dreaming of off shore fishing and besides, it's decreasing seas. That was the easiest $1800 I ever made.

Skip, be careful when stating specific degrees, ie, 90*. Each hull has a different righting moment. Speaking of moments, I'm surprised at this thread...we're pilots for cryin out loud. Y'all know moments, right?

What Henning means when he speaks of time to return to stability is better expressed as the distance between CG and Center of Bouyancy. This is the Righting Arm which itself is expressed as a torque about the CG.

My'gosh, you're all pilots, you should know arms and moments by heart.
 
BTW: lee shores scare me. Probabaly a combo of my experience and reading Tristan Jones.
 
Skip Miller said:
OK, there is a good sea running but "terrible storm"? I don't think so.

Modern cruise ships are so top heavy that they usually run for port (or calm seas) whenever the sea kicks up. How this one got caught might be an interesting story.

It looks to me like the ship has a pretty good list to starboard; it seems like the rolls go much further to starboard than to port, but that could be the camera angle. How much further do you think she can roll without going over?

Can you spell (I almost typed "smell") barf?

-Skip

http://www.liveleak.com/view?i=dd0_1174965550
Click to expand...
I just watched the vid. It's camera angle...and I would have given an E ticket to be in the crow's nest, fo's'cle as runnerup.
 
Read The Perfect Storm, unlike the movie, it is full of information on the self-righting virtues of sea going vessels. It is believed that the fishing vessel that was the focus of the story capsized because of weighty modifications to the upper decks without proper righting tests.
It really was a good book, and as ususal mucj better than the movie.
 
I remember the big concern about ice anytime we went up north in the winter - the added weight on the various masts/stacks/etc made a big difference in the vessel's roll profile. Keeping the ice off with scrapers/hammers/steam hoses was miserable duty.
 
A friend of mine added 10' on the waterline and some superstructure without any stability testing. It changed the roll of the hull. Subsequently the boat was lost on the maiden voyage in a quartering sea. The eeire part was it acheived neutral bouyancy about the same depth as the length of the EPIRB tether. The ghost vessel continued to transmit for 7 weeks but was never found by vessels in the area. His body was never recovered. In the CG report a vessel capt said he was right on top of the location of the signal but nothing in sight.

And yes, many people told him so.
 
I was once on a cruise ship that took green water over the bow. It took a long time for the water and spray to clear. I wished I brought my camera since the picture wasn't one you'd find in the travel brochures, but I was just walking around on deck.

We were coming back to Hawaii from the Kiribati islands and the trades were really kicking up.
 
TMetzinger said:
I remember the big concern about ice anytime we went up north in the winter - the added weight on the various masts/stacks/etc made a big difference in the vessel's roll profile. Keeping the ice off with scrapers/hammers/steam hoses was miserable duty.
Click to expand...

Thet's why on a well built ice boat you run steam pipes through everything to keep it all warm. On a sunny day in Antartica we'd suntan on top of the wheel house laying on the heated deck, even though it was -10, with no wind, the sun and hot deck, it was really nice.
 
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