Grand designs and heavy seas

Without a doubt, cruise ship design has progressed by leaps and bounds over the past decade or so. However, while the facilities of offer have improved, something else seems to have received much less attention: seakeeping qualities of these grand designs.

Look at a photograph of any modern cruise liner in dry dock, taken from bow. You will notice that the lines of the underwater hull are fine indeed. Now let your eye move up, above the waterline and a little bit away from the sharp bow: voila! These modern ladies of the sea have very fat cheeks.

The use of modular cabins for both passengers and crew mean that space is needed to accommodate these rectangular modules that arrive on board with curtains hanging and taps plugged on the walls. Hence the need for space in the hull. No longer do we see ships with fine lines above the waterline as was the case in the days of the liner era.

Any practical implications?

Oh yes: modern cruise liners are prone to heavy slamming, which follows from the fat cheeks just above the waterline hitting the bottom of a wave in heavy weather. A good slam will make you wobble on you feet and send unsecured items flying from table to the floor.

Stabilisers that virtually all modern cruise liners are fitted with are of no help against the pitching movement - the alternate up and down movement of bow and stern - although they are very good at eliminating sideway rolling.

In late 2008, I spent five days on a 80,000 gross ton-plus modern vessel in force 9 to 10 from Civitavecchia to Southampton: the ship was slamming badly and speed was reduced to 10 knots, resulting in an 18 hour delay on arrival.

A senior cruise industry official said a few years ago that modrn day naval architects may not quite know the sea as their predecessors did: they come from university to work at shipyards and design offices, without experience from working at sea. This may well be the case.

In any case, only ships change. The sea does not.