Italian Liner Sinks - lights go out

Actually, the captain has been arrested, in part, for abandoning the ship.

http://www.chicagotribune.com/news/sns-rt-us-italy-shiptre80d082-20120113,0,67784.story

 

I gotta closely watch that ship prefix. Around here, Polar Star defaults not to MV Polar Star, but instead to USCGC Polar Star, currently on a multiyear 'cruise' moored to a local dock. Hopefully it will be cruising through the ice floes again in 2013, if its refit is completed on schedule.

 

A naval architect on another forum I frequent posited that the ship may have settled onto a rock that caused it to tip over on the other side once it became negatively buoyant, and this was exacerbated by the fact that she is a top-heavy design. Considering the area she was stricken in, that might be a plausible explanation. She is, after all, in only 50ft of water and draws about 25ft if she is a standard cruise ship.

 

This is the same point I made. Once the ship is grounded and taking water the vessel will settle toward the ungrounded side. This is because the grounded side is supported, being held up as the ship settles. Once listing starts, free water will flow to the low side, becoming self sustaining.

Large ships are not very stable as compared to small boats. They don't have to be, since wave and wind are the same for both. Little boats travel through proportionally larger disturbances.

An additional problem is human comfort. Stability is expressed mathematically by a factor called "metacentric height". Metacentric height is the distance between a ship's center of gravity and its metacentre, which is essentially its center of buoyancy.

It's a fairly easy concept at simplified levels: gravity pulls down, while buoyancy pushes up. The larger the distance between the two forces, the longer the arm and hence the greater the leverage. With a ball floating in the water, the metacentric height is zero: the center of gravity and the center of buoyancy are at the same spot. The ball freely spins to any orientation. With a buoy, the weight is down low and the float up high. The buoy sticks up out of the water.

So to make a boat or ship more stable, we put more weight lower in the vessel, or make the boat or ship wider up higher to raise the center of buoyancy. So you might ask yourself why the designers don't make ships more stable? This is where it gets interesting. It's easy enough to increase stability by increasing the metacentric height, but as you do so the righting motion becomes more violent. You get a boat that snaps instead of slowing rolling. The ship might be stable, but the passengers on the ship would get thrown from side to side, ending up as bloody grease spots on the walls.

Because of this need for easy motion, the metacentric height on most big ships is only a few inches. They can't right themselves if pushed over very far. Fortunately big ships don't often get pushed over very far, except in sinking situations.

Small boats, like cruising sailboats, will have much longer metacentric heights. They are designed to self right well past horizontal. But because the boat is smaller, the righting forces are also smaller, so you don't get as much snapping as you would on a big ship.

Tom

 

The safety requirements, crew training, and general efficiency of vessels varies widely by country of registration. There is a reason, as I stated before, that many vessels fly Liberian flags as a flag of convenience.

Put in other words, not all cruise ships are the same. Choose wisely.

Tom

 

This comes down to the size and structure of ships. While enormously heavy, ships are not very strong. We tend to picture them as full sized versions of model boats, where an enormous hand (or Superman) could reach down and pick one up. In reality ships are more like tinfoil boats. If you tried to lift one it would crumple into pieces.

Ships are designed to be supported by water, which provides relatively uniform support over the entire surface of the hull. Any point loading, like a rock or even a sand bar, will most likely punch a hole into the hull. While big and strong, ships are fragile.

Submarines are a bit stronger for their size, due to the need to survive pressure, but the same basic factors are at play. Trying to grapple and lift a sub has two main problems: 1) The sub is very, very heavy; and 2) The sub will break into pieces unless it is uniformly supported over the entire hull. It's not easy to do, even without a deadline.

Tom

 

Been thinking more about the emergency generator and the lights
going out.

If the emergency generator was located on the main deck on the
side the ship capsized towards, the generator would be submerged...
Bingo, all lights out.

On the other hand, if the emergency generator were on the non-
submerged side, I can see some possible fuel related issues related
to availability. Typically, the emergency generator fuel tank would
be welded or otherwise fixed to a bulkhead, wall, above the generator
to give a slightly positive feed pressure. Fuel would be drawn off
through a fitting on the top of the tank, with an internal suction tube
leading down, and ending close to the bottom. (This arrangement so
that there are no fittings on the bottom of the tank itself that could leak
over time.)

If the tank is lying on its side due to the capsizing, depending on
whether the fuel outlet is in the center or off near the side of the tank,
fuel availability would be: outlet high - no fuel, outlet in the center -
1/2 tank volume available, outlet low - full tank volume available.

To confuse the matter, there is the possibility that there was a flexible
suction line inside the tank.

There are also possible fuel availability issues related to the location
of the fuel tank vent; you have to let air in to get fuel out. The vent
would be located on the top of the fuel tank. If in the capsizing the
vent were covered that would restrict fuel availability. If the generator
didn't shut down immediately and continued to run, it would pull sea
water into the tank which, depending on the particular arrangement
of vent and suction, would in time kill the generator due salt water
ingestion.

 

Thanks for the explanation.

With all the Titanic comparisons being invoked, come to think of it the matter of a ship's fundamental fragility is dramatically demonstrated by that wreck: in a dead flat sea in fair weather the ship was shattered by its own flimsiness, first when the stern broke away when the ship had tipped high enough, and finally when it struck bottom and was smashed, its heavy steel plates crumpled and torn and dispersed like confetti on the sea floor, as if it had been made of tissue paper.

 

Exactly. Even though the materials are strong, steel, iron, aluminum, or such, the strength is small when compared to the overall size and weight of a ship.

You see this demonstrated when a fly buzzes into a window: "bzzzz, whack, bzzzzz, whack, bzzzzz whack". A housefly crashes into the glass, bounces off, and goes back for more.

Now take an airliner that ticks the top of some trees, resulting in a crash, fireball, and the death of all aboard. The aluminum skin of the airliner is much stronger than the fly. An aluminum fly swatter can easily crush a fly. But the aluminum skin of the airliner is not very strong when compared to the weight of the aircraft. The fly is strong for its size, but not strong in absolute terms.

The weight of an aircraft is distributed over its entire wing surface. The aircraft is easily broken if even a small fraction of this weight is applied to a small area of the skin. The same is true of ships.

Tom

 

Tom's explanation of the relative fragility of large ships is well stated.

In typical operation, the mass of the ship is relatively evenly supported
by the large expanse of its bottom and submerged sides. Problems
occur when the thin skin and its supporting matrix of vertical frames
and longitudinal stringers is asked to support a large localized point
loading, such as occurs in a grounding or collision.

I'm sure that the cruise ship was required to have watertight
subdivision below the main deck. This would mean that the hull was
divided into numerous watertight compartments. Typically, the
compartments are sized such that at least two of them can be fully
flooded and the vessel remains afloat. Except on warships where heavy
below the waterline damages must be considered, it is rare to have
watertight bulkheads running fore and aft.

The fly in the ointment is that there are watertight doors between some
of the compartments. These are meant to provide the crew with
convenient access to spaces that need to be visited during the
operation of the vessel. Typically, the watertight doors, WTD, are
closed except when actually in use. Unfortunately, the crew can get lax
and leave the doors open for frequent passages. This is especially true
if the WTDs are manually activated. From the amount of flooding in this
case, I would guess that some of the WTDs in the engineering spaces
were not closed.

Sometimes the WTDs in the engineering spaces are permitted to
remain open. In cases like this the WTDs are connected to a rapid
closing system. It is easy to close a WTD rapidly if it acts like a
guillotine, closing vertically from above via a remotely controlled
release. Of course, Once the vessel has considerable list, leaning
to one side, such WTDs don't operate well, if at all.

The results of a full, impartial investigation should address issues such
as these. I would suspect that such an investigation and report will take
at least year to complete and publish... Hmm, it's more likely two years.

Barring some kind of really momentous findings -- this would not
include simple negligence or mis/mal/nonfeasance -- the media and
the rest of us will have by then moved on to other things of immediate
interest and not see the findings.

Que sera, sera.

 

Thanks for this explanation. It makes perfect sense, but is something I'd never thought of before.

BTW, when I sailed on the Lord Nelson, I'd have been thrown out of my bunk with every roll of the ship if it were not for the nets on the bunks to hold us in.

That's what I said!

 

Current news reports quote the captain as saying "...were at least 100 meters away from the rocks." 100 meters is not enough clearance from a hazard for normal navigation. In channels and other areas of restricted navigation you may get this close to a hazard, but not in open water.

Until I hear anything different, my first guess is that this is a classic case of being lulled by modern electronics. You sit there with a chartplotting GPS and think that what it shows you is absolute gospel. I believe they cut it close to the rocks, only to find that charts and GPS can have some error.

I did this with my sailboat the first year I had a chartplotter. I was going into an unmarked narrow entrance to a favorite anchorage. I had been in there a dozen times before, each time relying on careful observation and bearings from the shore. This time, with the GPS chartplotter, I thought "this will be easy" and just steered down the middle of the narrow channel. I put us hard aground - the first time I ever grounded going into that spot. The GPS had lulled me into poor judgment.

Modern navigation gives a feeling of authority. It's precise, official, and so easy to use. But it can be wrong. GPS can go off by thousands of yards. Charts can be misplotted. Additional obstacles can exist.

Modern navigational aids make boating safer and easier, but once in awhile someone gets bitten by complacency. I suspect this is one of those times.

Tom

 

I took a fairly extensive behind the scenes tour of the Holland America MS Oosterdam a year ago. We saw much of the 3 decks below the paying passenger area, didn't see the engine room, crew quarters or fuel storage. The watertight doors we saw were open and automatic with some strongly worded warning signs with words to the effect that the door could smash you so don't be in the doorway if the alarm has sounded. The areas we went through were fairly high traffic areas, the doors in less traveled areas might have been closed.

I wish I had retained more from that tour but it was easy to get disoriented going up and down between decks with someone talking to you and no outside references. We did see the morgue.

 

The Captain is now claiming the rocks he hit weren't on the chart. Well, he's correct, now - the rock he hit isn't on the chart anymore, it's broken off and embedded in the hull.

I've got complaints:

First, the news reporting on this chart business is atrocious. The reports don't show the charts - nor reflect any news investigation of the charts! For such a critical point you'd think that's be the first place they'd go - as well as to just what kinds of nav and sounding equipment were on board that liner. Instead we get a few seconds of interview with the Captain - a Captain desperately trying to put blame elsewhere, a personality automatically to be distrusted. The reporting here is exasperatingly bad.

Second, even if the actual rock itself wasn't marked as a cross on the chart (and probably wasn't), the rocky character of that coastal water is no mystery. Some reports indicate the ship was steered outside the standard departure route. If that had been deliberate not just the Captain but all conning officers are culpable.

Third, where's the pilot? I thought only pilots could conn ships in & out of harbors - or does that only apply in certain countries? Although, one would think an international cruise ship company would insist on pilots being used regardless of whether required or not. Lots of questions here that could, with the most elementary of reporting effort, throw more light on what happened.

This was the best I could find as to nautical charting - the wreck is right at the point of land that points to the 62 with the "sk" notation just beneath it, just north of the harbor breakwaters (with their two lights, shown as green and red flashes).

Digital nautical charts from 1yachtua.com Western Mediterranean and Ionian Sea.

 

"When navigating by GPS it is still a good idea to occasionally look out the window."

Between someone being on watch on the bridge, radar and GPS someone has a lot of 'splainin to do.

The wouldn't have seen the underwater reef on radar but they would have know they were a few hundred yards from shore instead of a few miles from shore like they were supposed to be.

 

Another one, not as bad
The Freeport News - MSC Poesia runs aground; Tourists still receive warm Bahamian welcome

MSC Poesia ran aground in the Bahamas yesterday. (Jan 14th)

MSC? Mafia Shipping Company?

 

Following is very general information, I do not know what the
specific pilotage requirements are in the locale of the grounding.

"Pilotage" is a strange beast. It is implemented differently in different
jurisdictions, countries. Generally speaking, the pilot is charged with
specific and detailed knowledge of local conditions. When a pilot is
engaged he/she acts as an advisor to the Captain. However, the
Captain may elect to turn over the actual control, "the con," of the
vessel to the Pilot. Should the Captain so elect, he cannot delegate his
individual responsibility for the safety of his vessel, crew,
cargo/passengers.

In some jurisdictions, such as the US, a ship's officer may hold both a
license (Captain, Mate, etc) and a pilotage endorsement or
endorsements for local waters frequently transited. Due to the difficulty
and time consuming process to get a pilotage endorsement, this is a
relatively rare occurrence. That said, it could be advantageous for a
vessel operator to engage a deck officer with relevant Pilotage
endorsements. In this case the Captain would not have to engage a
local pilot and save considerable money.

Here on the Chesapeake Bay there are not only mandated Federal and
state bay/harbor pilots, there are also state mandated Docking Pilots
whose duties are specifically and solely related to bringing a vessel to
safe mooring alongside a pier.

 

More info is coming out. Large ships carry AIS.
[ame=http://en.wikipedia.org/wiki/Automatic_Identification_System]Automatic Identification System - Wikipedia, the free encyclopedia[/ame]
The AIS tranmits the ships position, heading and speed at frequent intervals so other ships in the area with AIS will be aware of other ships around them. There is large hobbyist following of AIS, often hams, who record AIS data and publish it on the web so the general public can see where ships are.

As amateur AIS followers start to piece together the data, we are going to learn about the ships actual course before it makes the mainstream news. A good start is here
SeaNews Turkey - Costa Concordia: A major navigational error, or what?

Costa has also buzzed that island closely before.

A video of a Costa ship passing close by the same area at high speed is here.
La nave Concordia vicino al Giglio - Video - Corriere TV