Saturday, 21 January 2012

Two observations on the Costa Concordia

Firstly an observation. As Richard North posted several days ago, stock pictures of the ship in port show a large EU symbol on the bows, aft of the ship's name. Since then I have searched largely in vain for a shot of the waves lapping around the symbol as it slowly sinks beneath the sea. Aerial photos of poor definition show that it's still there, but none of the flush of hi-def close up pics of the wreck show this at all. Can there be a little bit of news manipulation here?

Secondly, many have commented that the ship is lying on the opposite side to the gash in her hull, which is counter-intuitive. I can think of only one explanation, based on the free surface effect. In a vessel with a high centre of gravity, turning to port or starboard, or even the operation of bow thrusters, may induce a 'lean' in the direction of turn. Normally this doesn't signify, but with an engine room deep in water and without longitudinal bulkheads, this may cause the mass of water to shift to the opposite side of the ship beyond the point of recovery of vertical stability. Unlike proper sea going ships like the QMII, which can take an Atlantic storm, modern cruise liners are like steel shoeboxes. If this is the case, I would expect MAIB to comment on the sea conditions in which it is safe for such British flagged vessels to operate. 

13 comments:

ancien matelot said...

Kindly stop making waves. You are making me seasick!

Oldrightie said...

Richard's site has an animation which shows exactly why she lies as she does. The initial impact on the port side was at relatively high speed. As the vessel "glanced" off and was fatally crippled by that collision she was manoeuvred with the decaying speed and bow thrusters into a right hand turn in a vain attempt to head for the port. By the time she was heading 180 degrees from impact the speed was down to less than 1 knot. From here she drifted onto the rocks and sand banks, where she lies.

Anonymous said...

Interesting observation on the blue ring piece flag.

I wonder, a metaphor as it is for the Great EU shipwreck - are the 'powers that be' in Brussels so prickly, that the painted flag is unsubtly being airbrushed - I think you are right Raedwald and I also think this is just how the colleagues will rewrite European history and efface it from the consciousness of future generations - God forbid: if their hegemony survives.

Greg Tingey said...

Odrightie has it ...
The ship, after gashing, turned to Starbord, then sharply round to Port, this facing SSE in an attempt to make the port entrance.

Didn't quite make it.

BJ said...

As we're discussing reasons for a ship going over - free-surface - I always wonder about the GM of these liners.

The ability of a ship to right itself after tilting must be affected by all that superstructure.

Budgie said...

No need to invoke the free surface effect. Nor is the ship position, lying with the gash uppermost, counter intuitive.

The 230ft gash is in one side (as far as we know at the moment). At the time of the incident, as the hull rode along the rocks (which must have protruded into the hull to make the gash) the rocks will have supported that side of the ship. So the rocks will have behaved like a fulcrum for the ship during time the ship was on the rocks.

At the same time tonnes of water will have been gushing into the gash in the hull. My rough back of the envelope calculations (yes, full of assumptions I know) indicate about 600tonnes/second average for a 70m x 1m gash, 4m under sea level. Assuming 15knot the ship will have been on the rocks for at least 10 seconds. So total weight of water would be about 6000tonnes. Plenty to settle the ship on the non supported side, since the dead weight is 10,000t.

I doubt if the normal design for stability (metacentre and centres of gravity and buoyancy) will have been able to cope with that.

Demetrius said...

Has the EU flag been replaced by a "Travelodge" sign?

Anonymous said...

Surely, anybody with half a computer brian can just airbrush the flag back in again and then publish.

That would really piss 'em off.

Coney Island

Just Asking said...

Coney Island - Who's brian?

formertory said...

I was unwilling to believe it'd be possible to get all media to airbrush out the EU stars so went to Google images. Then I found this and laughed so much I forgot to look for EU stars.

Apologies if you've already seen it.

Anonymous said...

@Just Asking

I had to read that twice and then the penny dropped. :-)

Well it is Sunday!

Coney Island

Anonymous said...

The survivor descriptions of the sudden list to starboard imply te very strong possibility of "Loll" rather than "List". This implies a negative metacentric height and the excessive topweight makes the problem much worse. Without immediate action, the vessel will capsize swiftly and without warning. The heel to either beam will not be affected by weight, it is because the vessel is actually incapable of maintaining an even keel. Frankly, I think these vessels are top heavy even though they meet current standards as post-damage stability is likely to be insufficient to allow either safe evacuation or, as current regs state, for the ship to make its way safely to port without evacuation of the passengers!

Rossa said...

In addition to the EU flag, the decks were all named after European countries.

Polonia, Austria, Spagna, Germania, Francia, Portogallo, Irlanda, Gran Bretagna, Italia, Greciua, Belgio, Svezia, and Olanda (www.cruisedeckplans.com)

Can't airbrush that out of the picture!