Feature 4 | CONTAINER SHIPS APL’s statement of intent
In ordering ships optimised for operations at between 14 and 19knots APL has made the bold statement that container ships will never again sail at higher speeds. Te result is an order for 10 ships of 13,800TEU by APL at Hyundai Heavy Industries (HHI) using a concept borrowed from DNV
shipyards, class societies and designers from their own companies. Optimising ships for a particular trade is
O
not new, Maersk made the move when it set about designing its own ULCS, the Triple E class, but for APL and DNV the process has worked a little differently. According to Tor Svenssen COO of DNV
the initial design of APL’s newly ordered ships was inspired by his classification society’s concept ship, Quantum. Tis concept vessel included a number of radical ideas such as low ballast and a low block coefficient, of 0.57. Quantum was expected to trade between
Asia and South America, however, and APL has optimised their vessel for the Europe/ Asia trades. Tat said the major element, but by no means the only element, in making the vessels significantly more fuel efficient than traditional designs has been the slowing down of the vessel. Container ships were designed to operate
at around 25knots prior to the great economic calamity that befell global trade in 2008. Before the great crash ships were optimised at a single design point, the 25knot speed, hull lines, draſt and block coefficients were optimised for these speeds. In the post economic crash era vessels have
slowed down, mainly because the cost of fuel has increased dramatically, but also because in the boom years owners ordered vessels for trades that they expected to continue growing at around 15%; post the economic calamity they were being delivered into contracting trades and the new ships no longer had any cargo to carry. Ships were being delivered and being mothballed almost immediately. In this trading climate owners realised
there were significant savings to be made by slowing ships even by just a few knots. Tis meant that owners and operators could deploy an extra ship to their Asia/Europe
The Naval Architect October 2012
The operating profile consists of a matrix describing time spent at each speed and draft combination
strings, using up excess capacity and saving fuel. Owners, however, have generally expected ships to speed up when global economic growth returns bringing with it more cargo. APL, however, has taken the courageous decision to optimise its ships for the speeds ranging from 14knots up to a top speed of 23knots, making the statement that the company believes that container ships will never again, in the foreseeable future, operate at the high speeds seen before the economic crisis. Svenssen confirmed the partners’ view:
“Container ships have slowed down for good; there is no compelling argument for high speed.” Design partners at DNV, HHI and
APL recognised that container ships were operating at between 14 and 19knots for 90% of its operational time and that ship designs needed to be optimised for that range speeds. Travelling at up top 23knots is possible but the quicker the ship goes the less efficient it it. DNV analysed the operating patterns of
existing container ships and then developed a future operating profile, consisting of nine speed and draſt conditions, as the basis for the design of the APL vessels.
“We had been through a similar exercise for
the design of Seaspan’s 10,000TEU ships, but they are not owned by a liner operator so they are only optimised for a speed range and not for a particular route,” says Svenssen. Te APL vessels have also had the hull lines
changed and the major component here is the bulb which was redesigned using CFD to reduce resistance from the bow wave. At the rear of the hull the wake drag has been further reduced, says Svenssen. “Ships can be improved by cutting part of the hull off and redesigning it, even some existing ships could be improved,” he added. Te aſt is optimised to allow for an even
flow of water into the propeller and an even wake field. “Te focus is to do a good job on the hull design,” explained Svenssen. Computer analysis allows designers to
explore a range of variations in hull design and to calculate the effects of changes, the design calculations can then be further evaluated and tested through model tests, explained DNV. Design variations meant that the APL
hull form remained “relatively fine, so it had a better flow, but with a high beam for an improved cargo capacity. Te ships will be 368m long, with a beam of 51m and a block coefficient of 0.67, says Svenssen.
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wners are looking to optimise designs for ultra large container ships (ULCS) by bringing together
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