When ship designers and other mariners refer to one of the relentless enemies of operational efficiency, they call it slime. It’s not meant as an insult.
Hull designs and coatings play an enormous role in Royal Caribbean’s constant efforts to squeeze every efficiency possible out of its newbuilds and existing ships to shrink its environmental impact, cut costs and increase revenues.
Anshul Tuteja, RCL director of energy management, says the target value for each new vessel is 15 to 20 percent better than the previous build.
“From the fleet perspective,” he continues, “our target is to improve at least two to four percent every year in terms of energy efficiency.”
It begins with the contract between RCL and the shipyard. Where other lines contract for design speed, RCL ships are built according to an “energy efficiency contractual value,” Tuteja says. “This is the amount of fuel we should be consuming per number of double occupancy cabins. This number is not just about propulsion. This is also about service power, meaning the hotel power that we use – chillers, galleys, refrigerators.”
“There are always things which can be tweaked, new appendages added or removed,” Tuteja says.
Already taken into account is slime – a layer of algae, bacteria and other marine life at the bottom of the food chain but the root of extraordinary problems for the owners of every craft from small fishing boats to container ships to such mega cruise ships as those in RCL’s Oasis class.
When slime tenaciously attaches to a ship’s hull, other forms of sea life show up to feed on it as they, too, latch on and dig in. It is especially troublesome in warmer waters. Unchecked, the fouling grows down from the hull in huge, truly grotesque agglomerations. The slime layer alone cuts into operating efficiency, increasing fuel consumption and environmental impact while eating up revenue.
And the more the biomass grows, the more trouble.
So a very dynamic market in highly specialized commercial hull coatings has sprung up, Tuteja says, and competitive manufacturers have to continually improve their products to compete.
One such coating used on RCL ships is “self-polishing,” its top layer peeling back and away, taking biofouling with it, as the ship picks up speed.
Other energy efficiency efforts in RCL hull design include:
- Maintaining a robust dashboard monitoring every ship’s monthly performance for early warning of hull declines.
- Constantly testing scale models for new and better hull lines using computational fluid dynamics.
- Picking up 0.4 to 0.6 percent more propulsion by grinding hull welds flat on new builds and existing ships – if it makes business sense to do so.
- Building all new ships with a bulbous bow or “bulb” that rides just under the waterline at the front of the ship to fend off the waves created by the ship itself, contributing to drag. If economically feasible, older ships are fitted with a bulb.
Though not done for cosmetic purposes, Tuteja says, the procedure is often called a nose job.