‘Nose job’ is all about performance, not looks

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Sometimes, for reasons that have nothing to do with appearance, a Royal Caribbean ship needs a nose job.

Regardless of the grace designed into the ship’s bow or the streamlining of the prow – the underwater portion of the bow – the ship’s fuel efficiency can be improved with the addition of a large and very peculiar-looking protuberance.

It is not an atavistic ram, a dummy torpedo or a solid counterweight, though it looks like it could be any of these. It is not meant to carry anything or be visually attractive.

“The biggest purpose of the bulbous bow, what they also refer to as ‘the bulb’ in the front of the ship, is to reduce wave resistance,” explains Anshul Tuteja, RCL director of energy management. “When the ship moves in the water it generates waves, and when they come in contact with the hull – as the hull is pretty big – it causes drag.”

“What the bulb does is reduce the wave-making by the ship and in consequence the wave-making drag on the hull so the hull is subject to the least amount of resistance from the waves.”

It goes against intuition to accept that this blunt object cleaves the water in such a way that it creates less drag instead of more, but ships have been using bulbous bows for decades to do just that.

The bow of a ship in motion actually creates not one but two sets of waves that cling to the sides of the hull before moving aside. The bulb, which protrudes ahead of the prow just under the waterline, gives the waves an early start. Ideally, they move away from the hull before adding their own drag.

None of these bulbs are “off the rack” or “standard” designs. Each one is custom designed, tested and fitted to its ship for maximum efficiency. And all are notoriously difficult to fabricate by shipyard welders because of the precision required.

In general, Tuteja says, the wider the ship’s beam (its maximum crosswise measure) the bigger the bulb for pushing waves farther away from the hull.

In recent years, the science of computational fluid dynamics (CFD) has made pre-construction models of each new RCL ship precise in hull design, including the bulbous bow, Tuteja continues.

“We’re able to exactly predict what kind of hull lines will be required for the optimal operation of a given vessel,” he says. “We know where the ship will be deployed, what will be her average speed and based upon that we try and optimize our hull lines.”

That’s how it’s done on newbuilds. Older RCL ships can be retrofitted with a bulbous bow if the savings in fuel and other efficiencies make a case for the expense of doing it.  There’s a CFD test, a determination of the operational impact of the job, the cost of materials and labor, and the lost revenue during dry docking among others.

That, in a maritime slang, is the “nose job.”