Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Sunday, September 15, 2013

One Risk in Parbuckling the Costa Concordia: Crushing the corner

A good animation is here from Crowley Maritime, which owns Titan Salvage.
Using snapshots from that film, which is a head-on view of the ship in which the starboard, or right side is on the left of the image, I labeled the major parts mentioned in this post.

This diagram may help explain some risks that salvors off Giglio will be managing tomorrow (if the weather holds), when they'll have to keep a close eye on concentrations of stress in the hull as it rotates under pull from the parbuckling cables and later the weight of the sponsons. The salvors have been pretty clear that things will bend and break during the process ... hopefully not the bigger things.
I'm guessing one risk they'll be watching will be a temporary concentration of weight on the starboard edge of the hull (see yellow arrow, below). The concern is weight of steel not fully offset by displacement in water: that's hull, fittings and the new sponsons, which will be mostly out of the water at that point.

Ship designers sometimes call this area of the hull, where horizontal plating meets vertical plating, the "turn of the bilges." It's the location of a stabilizing fin called the bilge strake, depending on vessel details. Here's a diagram from -- see the highlighted yellow portion.
Recall that no seagoing cranes will be attempting to hold the weight of the hull off the seafloor. That's the nature of parbuckling: the structure has to hold up while a lateral, rolling force is applied.
But the good news is that a world-class crew is on the job. Wreckmaster for Titan-Micoperi is Nick Sloane of South Africa, who came to this job from the wreck of the Rena off Tuaranga, NZ, which I've covered in a series of posts including this one.

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