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24 November 2007

Can we talk about how it blows my mind that a hole the size of a fist can sink a cruise ship?
Can you describe the blowing?
posted by stavrogin 24 November | 00:37
Aaaargh. Now see, that's why, despite my inbred love of the sea, I can't ever take a cruise.
posted by jrossi4r 24 November | 00:38
As someone who just took a cruise, it's just wild to think about. Cruise ships are gigantic- the one we were on was even on the small side, but it still took a long time to walk from front to back, and the amount of stuff they crammed onto it... wild. I keep making a fist and trying to imagine how, HOW.
posted by ThePinkSuperhero 24 November | 00:40
There's nothing unusual about that! Holes in boats are bad.

It's all about balance. Water weighs eight pounds a gallon. Ships are divided below decks with watertight bulkheads into sections which isolate in-flowing water. It doesn't take that much water to throw a ship so severely off balance that it starts to list dangerously. Once it lists, other portals begin to fill with water, and gradually the ship becomes heavier and heavier until the weight of the water overcomes the bouyancy of the vessel.

This didn't happen quickly. It seems as though there was about an hour and a half elapsing between the puncture and the decision to get into lifeboats. And then another 12 hours or so until the ship began to sink. A lot of what ship design has been about since the days of the Titanic is how to slow the sinking process to allow enough time for people to make decisions.

Anyway, as a mariner myself, I would certainly want to think twice about the Jonah effect of going on a voyage called the "Spirit of Shackleton" tour.
posted by Miko 24 November | 00:43
No matter how big they are, I'd always feel claustrophobic. If shit goes down, there's nowhere to run, man. Nowhere to run.
posted by jrossi4r 24 November | 00:45
Cruise ships are built to make money.The crew are slaves,the ship
is cheaply made,god I could go on and on.Anyone who thinks it's romantic must be blissfully ignorant,or don't research their holiday facts.And yes,jrossi4r,if it goes down,you are fucked,as they do not expect it,and almost all are poorly trained.
posted by whiskeychimp 24 November | 03:20
Further to Miko, its a relationship between size of hole and the depth under the water. Even a small hole six or eight feet below the waterline can let in an amazing amount of water due to the water-pressure forcing it in - it sprays in, doesn't just flow in. The table on this page about halfway down illustrates this:

hole = diameter of hole in inches
b/w = feet or inched below waterline
Figures are in gallons per minute


hole 6"b/w 1'b/w 1.5'b/w 2'b/w 3'b/w
1" 13.96 19.60 24.20 27.80 34.0
2" 55.49 78.60 96.10 111.10 136.10
4" 222.10 314.30 378.70 444.50 544.40
6" 499.60 707.20 865.30 1000.20 1225.00



So, a 1 inch hole 6 inches below the waterline lets in about 14 gallons per minute, while the same size hole three feet below lets in 34 gallons per minute. A 4 inch (fist sized?) hole three feet below the waterline is letting in 544 gallons/minute, or, 32,000 gallons/hour. If the hole i six feet below the water, double that, and if it's a six inch fist, not a 4 inch fist, you can double the doubling!

Scary stuff.

This ship was built for the antarctic and had also done the NW Passage without an icebreaker, so not your typical cheap (basically, disposable) cruise ship. Obviously something went terribly wrong but the table shows just how fast water can come on board.
posted by rumple 24 November | 04:01
Wow, rumple. That's amazing and scary; great info.
posted by taz 24 November | 06:08
"British Coast Guard spokesman Fred Caygill told The Associated Press the ship had a hole "the size of a fist" in the hull.

We believed it has been hulled, it has a hole the size of a fist and some cracking in the hull of the ship, it's taking water and it's listing about 21 degrees," he said."

"Some cracking" meaning that this was more than a simple, relatively smooth edged hole, too. Many types of steel become much more brittle in cold, and although this has been known and considered in steel specified for ship hull construction since sometime after WWI, the effect can only be minimized through metallurgical selection, not eliminated. This problem has been debated a major factor in the Titanic disaster, too. From "TABLE OF METALLURGICAL PROPERTIES OF NAVAL ARMOR AND CONSTRUCTION MATERIALS© by NATHAN OKUN (Revised 10 July 2002)":

"TOUGH - Resistance to cracking under sudden impact loading where the metal has minimum time to adjust to the force before it breaks or tears open. Usually considered the opposite of brittle (see above). The Charpy and Izod toughness tests were developed after World War I to measure how tough a material is: They take a long sample, hold one end in a vice, put a notch or groove in the sample just above the gripping point and then hit the sample sideways just above the notch/groove with a calibrated swinging or dropping hammer so that the sample must fold sharply at the notch/groove. How hard the hammer must hit the sample before it breaks or tears at the notch/groove and the manner in which the failure occurs measures the metal's toughness--tough materials should fold virtually double before splitting in two, while brittle materials snap off like pieces of a china cup dropped on a hard floor. Toughness is dependent on temperature, where cold temperatures make the metal object more rigid and thus more brittle and shrinkage of the Iron crystals weakens the bond between them (see REFRIGERATION, below, for more details on this). The Charpy and Izod tests also give the energy needed to break the sample, which is an absolute strength parameter. I only consider toughness relative to the tensile and yield strengths of the material, where to me wrought iron is very tough (stretches considerably under load so it is hard to crack or break) even though it can be torn apart more easily than some stronger, but more brittle, materials."

Alloying steel with nickel is the primary means of making it resist low temperature brittleness, but high nickel concentration makes steel difficult to weld, and very expensive to work from plate form. Again, from Okun:

"... A large part of Nickel's toughening ability is that its atoms are close enough to Iron to allow it to mix into the Iron crystals very thoroughly, but different enough to impede a crack trying to pass across these atoms, acting as a crystal defect--much like a speed-bump in a parking lot or piece of cloth in a zipper. Nickel also very strongly lowers the brittleness temperature of any steel containing it. It is used in amounts of 2-3.5% in the new, very high strength ship construction steels such as U.S. Navy HY-80 through HY-180, used primarily in modern, deep-diving submarine hulls. ..."

This is one reason why U.S. Navy submarines each have price tags north of a billion dollars. I think a board of inquiry will find that steel types like USN HY-80 were not used in the construction of this commercial vessel.

The cracking reported is a telltale clue that what appeared to be a minor impact puncture actually resulted in much more serious structural hull failure. With each wave, the hull was flexing at the cracks (at first, probably slightly, but with time and wave action, more and more), letting in much more water than just the puncture hole alone would have, but more seriously, probably extending the cracks themselves through stress fatigue. In that kind of failure, patching or internally shoring the hole itself is nearly useless, as the vessel will ultimately breakup on wave action, if it doesn't rapidly sink first, from the additional water coming in through the relatively large area of the wave flexed cracks. And it's a major reason why normal ships should always operate very carefully in cold, icy waters.
posted by paulsc 24 November | 06:26
It's impressive to me that the evacuation was so successful. Must have been very scary to be out in lifeboats in icy waters. It will, however, be the best adventure vacation story ever.
posted by theora55 24 November | 10:58
Interesting info, rumple and paulsc.
posted by Miko 24 November | 14:12
I was thinking about that theora55- must have been so weird to be sitting there in lifeboats in the middle of the Arctic! Or to be on the cruise ship that turned around- when you're on a boat, you don't really know where you are, so you rely on announcements from the captain. How odd to hear "We had to turn around to pick up 150 people who evacuated a ship that sunk".
posted by ThePinkSuperhero 24 November | 14:58
I would suggest that the cracking is the key - a single hole could be isolated into one compartment, but a horizontal crack could bridge across two or more compartments, meaning more water than the rest of the compartments could support. Often, is is as simple as having portholes open - as the water comes in and makes the ship list, the waters starts to flow in through the open portholes, filling more compartments, making the ship list more ....
posted by dg 25 November | 16:18
heh
posted by rumple 26 November | 03:18
The key lesson here is to avoid getting in fistfights with an angry Superman belowdecks. If he wants an extra turn at Shuffleboard, let him take his fucking extra turn.
posted by cortex 26 November | 13:03
Brilliant bumper sticker, || Rainbow Bunnies

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