Containerships have been with us for nearly half a century and goodness knows what old Malcom McLean would have thought if he could have dreamed that the system he effectively invented would have developed ships capable of carrying 20,000teu in a single hull. But while the ships have changed beyond all recognition and the individual boxes have got a bit bigger, the technology for lashing them on deck has scarcely changed

Lashing gangs still have to struggle with twistlocks on container corners and heave around great lashing rods and turnbuckles, just like they did on the first generation ships. The only difference is that while the boxes on deck were two high (which made experienced Western Ocean seamen doubtful), today we are looking at nine high on the hatches, with even a couple of tiers more contemplated on the very biggest ships, as their owners struggle to achieve scale economies. Lashing, as it was described recently, remains a “primitive” and sometimes dangerous activity

Lashing bridges help, of course, but there is a reluctance to make them more than about four boxes high, as it drives the crane drivers mad and slows them down as they have to lift over these fixed installations as they dig down into the holds. So above the racked tiers you will maybe find two or three tiers of rodded boxes, with the lighter tiers on top (you hope they are the light ones) secured by twistlocks. It means that human being are lugging around this stuff at great heights, while people on the quay have to jump around between vehicles detaching and inserting twistlocks.

Lashing equipment is heavy and bulky, requires regular maintenance and replacement as it gets a lot of wear as a ship works in a seaway. And we are still only now getting to grips with the forces on deck container stacks as ships roll and pitch and twist. The frightening phenomenon of parametric rolling still depends on somebody being alert enough on the bridge to recognise that it is about to happen and to alter course. It is not easy on a dark night and a long, confused swell. Even slow steaming, and optimising trim, we are now told, can lead to unexpected stresses on lashings.

Can anyone think of any better way of securing deck cargo? Semi- or fully-automatic twistlocks were once thought to be tremendously promising until slamming forces were found to release them at sea, which must have been somewhat alarming. We still sometimes lose a lot of boxes at once, which is, in our accident-intolerant age, takes a lot of explaining

Author:  Michael Grey                        Source: claymaitland.com

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