Container Ship Breaks In Two, Sinks

Cliff Stoll writes "Along with 7000 containers, ship MOL Comfort broke in half in high seas in the Indian Ocean. The aft section floated for a week, then sank on June 27th. The forward section was towed most of the way to port, but burned and sank on July 10th. This post-panamax ship was 316 meters long and only 5 years old. With a typical value of $40,000 per container (PDF), this amounts to a quarter billion dollar loss. The cause is unknown, but may be structural or perhaps due to overfilled containers that are declared as underweight. Of course, the software used to calculate ship stability relies upon these incorrect physical parameters."

Comments

Re:Declared underweight?

[mrchaotica]

I think a quarter-billion dollar claim might cause the insurance company to raise their premiums just a tad...

Hogging

[M0HCN]

It looks to me more likely the problem was excessive weight at the bow and stern rather then midships, the effect is called hogging and is a known way to snap a container ship (or oil tanker) in half, both have occured in the past.
Basically the keel (The BIG beam running all the way from bow to stern down the bottom of the hull) can only take so much sheer stress and if the weight distribution does not match the localised boyancy implied by the current displacement you can very easily bend the ship.

If and how it came to be loaded that way will be one of the things on the investigators list.

There is of course software used to look at this stuff but it cannot realistically be run on the dock during a very tight turnaround, so the declared weights are used as the only data available in advance of starting loading. Not only does that mess of linear algebra have to give a fully loaded ship with the centre of mass and moment of inertia in the right regions (Important for stability and handling), it must also ensure that the total cargo mass per linear meter is roughly the same as the boyancy of that meter of wetted hull at all times during the loading.

Further shippers will sometimes pay a premium for say not having a can of high value goods put in a corner on top of a stack where it is somewhat more likely to be lost, and some of those cans may be 'reefers' (Refridgerated containers) requiring both power and ventilation to remove waste heat, the problem swiftly becomes complex, doubly so as the ports stacking order also feeds into this if you want loading to go smoothly.

A nasty accident, but nobody died, and the hull and cargo will have been insured, so a better outcome then is sometimes the case.

Hope that explains why it is not just about total weight.