Costa Concordia, 80 deg list, really scary !!

It's not surprising that squat was under-estimated.
There was a very dangerous rule-of-thumb around for a long time that went something like:
"A ship squats one foot for every 5 knots".
Squat is definitely not linear in speed!

Back in 1992 or 1993, I heard anecdotes from Tuck and some people at MIT
concerning the speed of the ship and that it was late leaving Martha's
Vineyard. They all had a very low regard for many ship's captains -
dipsomaniac cowboys was the most charitable view. (The Exxon Valdez
disaster didn't surprise them at all.)

What shocked me at the time was that the QE2 captain (or pilot) thought
that clearing a submerged rock by 2 feet was Ok. That's cutting it very fine,
IMO.

It's interesting that Schettino is also claiming "uncharted" rocks as a cause.
And he was seen drinking before the accident. I wonder if we will see a blood-alcohol reading soon.

 

Squat has nothing to do with this disaster.

-Tom

 

If the ship was travelling at 15 knots in fairly shallow water then it might have played a part.

Just for interest: how do you know that it did or did not before the evidence is in?

 

The lateral version of squat/suction may or may not have also been a factor.

 

Based on where the damage is (above the turn of the bilge aft of midships) I agree that squat was not an issue. However the wall effect may have been. On the whole I feel that turn heel and drift angle have more to play in the actual physics of the allision. Even experienced mariners often forget that ships turn from the stern (which is why you immediatly turn towards an overboard person to keep them out of the screws).

 

Leo,

Squat happens, there is no doubt about it, that I am not disputing.

I know before the evidence is in because it has nothing to do with being that idiotically close for it to even come into account. The vessel should not have been within 1/2 nm of there.

-Tom

 

I agree, it appears that he was well off-course and far too close.
But squat occurs in shallow water, and the closer he was to shore the greater the effect.
Squat in water with a sloping bottom can cause a ship to slip sideways, but
I'd like to see the evidence and witness statements before making much of that.

I also mentioned "bank suction" as a possible contributor to the problem in
another thread, but we would need to see quite detailed bathymetry to
judge whether it would be significant. There do appear to be some quite
steep parts of the underwater profile along his course, but I would think
that they would have to be quite long to affect a very long ship.

 

I agree that it might not be the prime cause, but it might have contributed.
A stern-down trim and sideways slip could cause the ship to be damaged aft of
midships.

I just noticed that the captain admitted to being in water that was too shallow.
Does that mean less than the (static) draft? Or did he mean draft + trim at the stern?

 

http://www.maritime-executive.com/a...sible-consequence-of-costa-concordia-incident

 

So, it made a difference of 1 or 2 seconds before impact?

Wouldn't you sight accessive speed before concerning your selves with squat, vertical or lateral?

Once again, if due diligence were excercised, that ship would have been no where near a point where speed and/or squat would have even been a consideration.

-Tom

 

Submarine Tom, you're right, the main reason for the accident is the captain's wrong decision and wrong evaluation of ship's turning radius. Talks about squat, side-drift and other technical details should not be intended as a search for the reasons of the accident (which are in the captain's head) but rather as a discussion about the mechanics of the ships' motion which has led to the final grounding.

 

See the chart in this post: http://www.boatdesign.net/forums/op...oncordia-cruise-ship-41313-12.html#post519050
The shallow area the ship went across equals about 1 ship length - around 250-300 meters. The area where the depth is minimum is about half that length - 150 meters. If the speed was 15 kts, the passage over the shallow bank has lasted around 35 seconds (15-20 seconds to pass the zone where the fatal rock was living). I don't know how big the suction force from the bank can be, so don't know is that time sufficient to significantly change the ship's path.

 

Squat? drift? turning radii? The man drove his ship onto a rock, it ripped a hole in the bottom and the water which should have been outside came inside and the ship sank. Seems simple.

 

It's always very simple actually. A man get's killed by a gunshot, for example. He is clearly dead because someone has pulled the trigger, no big philosophy there.
But the autopsy will be done anyways - and sometimes it can reveal unexpected things.

 

Here is a copy of the report:
View attachment http___www.maib.gov.uk_cms_resources.cfm_file=_queen_elizabeth_2_pub_1993.pdf

That is not what is reported in the findings and subsequent investigation:

"..No specific discussion took place between the Master and the Navigating Officer with respect to establishing a minimum under-keel clearance for the planned passage. However, each was satisfied that sufficient allowance had been made..."

and notes:

"..With a mean stationary draught of approximately 32 feet, an estimated squat of between 12 and 18 inches and with little or no movement being experienced by the vessel, it follows that the Master expected a minimum under-keel clearance in the order of between 8 and 9 feet. .."

The cause was ostensibly out of date charts...and easy to note in hindsight. Also the actual amount of squat for the QE2 was a "guesstimate" and never actually known. Only later analysis and testing revealed a slightly different story that what was "expected" from old rules of thumb and guidance notes like M.930, and all at much lower speeds too!