New ACL series advances con-ro concept

The design for the G4 class con-ro was adapted by Knud E Hansen for ACL The design for the G4 class con-ro was adapted by Knud E Hansen for ACL
Industry Database

Long in gestation, ACL’s project for a new breed of deep-sea ro-ro containership (con-ro) finally reached the contractual stage in August, whereby the US-based owner entrusted the building of five 45,000dwt vessels to a Chinese yard, writes David Tinsley

Dubbed the G4 class, denoting the North Atlantic ro-ro pioneer’s fourth generation of thoroughbreds, the nascent series signals a major advance in con-ro design technology as well as in capability and performance.

The order underscores the level of commitment by Atlantic Container Line (ACL)’s parent Grimaldi to investment coloured by innovation, as the quintet embodies a new type of configuration providing for 3,800TEU containers plus 28,900m² of ro-ro stowage. The G4s will be larger and slightly faster, yet more fuel efficient and environmentally compliant, than their predecessors. The construction award to Hudong-Zhonghua Shipbuilding of Shanghai attests to China’s growing prowess and strategic intent as regards the production of tailor-made, quality tonnage.

Destined to replace ACL’s five 43,100dwt, G3 con-ros in transatlantic service, the G4 type reflects the company’s focus on combining increased flexibility and capacity with cost containment and a low carbon footprint. This complex brief has been addressed through innovative design.

In the collaborative, technical development process that spawned the G4 type, one of the design’s key features originates in a concept originating from the Danish firm International Maritime Advisors (IMA), tackling the problem of the high ballast requirement of con-ro ships.

In what may be termed a ‘conventional’ con-ro, the boxes are stowed above deck while the ro-ro freight is carried under deck. Because of the significant air space left vacant in the ro-ro areas compared to the denser stowage of containers, the cargo weight typically rides high in a con-ro, necessitating a large ballast volume to ensure stability in all conditions. IMA developed the concept of placing all ro-ro cargo midships, and loading containers in cells fore and aft of the ro-ro section, resulting in better utilisation of the hull envelope and optimisation of deadweight for cargo, since the need for ballast water is minimised.

Shipbuilding contractor Hudong-Zhonghua commissioned the Danish naval architecture firm of Knud EHansen (KEH) to adapt IMA’s con-ro concept to ACL’s requirements. Helsingor-domiciled KEH’s overall brief calls for the delivery to the yard of the full basic design package, including class drawings, hull and outfitting general design, machinery plant arrangement, HVAC (heating, ventilation and air conditioning) and electrical and automation design.

The G4s will be some 296m in length overall and 37.6m in beam, compared to the narrower Panamax gauge used for the G3 vessels, at 292m length and 32.2m width. Besides its beneficial influence on cargo intake, the wider beam enhances intrinsic stability. The 45,000dwt capacity is based on a design draught of 10.25m, although this rises to 56,700dwt at 11.5m maximum draught. The 28,900m2 of ro-ro garaging, incorporating hoistable ro-ro decks, allows for around 760 ro-ro units and 1,307 cars, and the 3,800TEU container payload will be accommodated within a lattice of cell guides not only in the holds but also on deck, and embracing a partial ‘open-top’ layout.

Overall stack heights, from tanktop to uppermost tier on deck, will be greater on the G4s than the G3 con-ros, as will car deck headroom. The bridge and accommodation will surmount the midships ro-ro block in the new ships, rather than being arranged aft as in the G3s.

The athwartships guide structure for deck-stowed boxes is apposite to ACL’s enviable record whereby the operator claims that it has not lost a single container at sea during the last 30 years. Weatherdeck container cell guides are a feature of the G3s, and have contributed to the series’ turnround performance, simplifying container spotting for the gantry crane drivers and dispensing with the need for stacking cones.

The G4s will supersede the G3 class of five Swedish-flagged ships that have been in service since delivery in 1984 and 1985 from former European bastions of merchant shipbuilding. Atlantic Companion, Atlantic Compass, and Atlantic Concert came from the Kockums yard at Malmo, in southern Sweden, Atlantic Cartier was built by Chantiers du Nord et de la Mediterranee (Normed) at Dunkirk, and Atlantic Conveyor was a product of Swan Hunter on the Tyne.

The G3s underwent hull renovation in 2004. The payload potential and mix of each remains at the top end of the con-ro league, given a container capacity of 1,850TEU plus around 1,000 cars and with ro-ro freight capacity equivalent to around 525 ro-ro units or some 1,000TEU. Sale to current or potential competitors would appear to be out of the question, leaving disposal for military use or scrapping as the alternatives.

Instead of the axial stern ramp used in previous generations, a MacGregor-Navire starboard quarter jumbo ramp was adopted for the G3s. The new, wider G4s will have a transom stern carrying an angled ramp of the same, 420t capacity as that of the existing ships, although the stern door will be narrower and of greater clear height.

As with the existing vessels, a single, two-stroke engine, direct-drive propulsion system will be applied to the newbuilds, to ensure a service speed of 18 knots. Although no details are available yet as to make and model of machinery, The Motorship understands that the power may be in the order of 22,000kW, corresponding to about 29,500bhp. The main engine in each of the G3s is a B&W (now MAN) 6L90GBE six-cylinder diesel developing an MCR of 23,800bhp (some 17,750kW) at 97rpm.

The considerable advances of recent years in marine engine design, yielding improvements in specific fuel oil consumption in companion with higher cylinder power and reduced noxious emissions, together with scale economies, have a fundamental bearing on the step change in unit transport costs promised by the G4 programme. Relative to the G3s, ACL says that ship speed will be increased by 10%, yet fuel consumption per TEU will be reduced by 50%.

The efficacy of the design is such that each G4 will be equivalent to a 6,500TEU containership in terms of earning power and economies of scale, but with far lower operating costs. All five new vessels are scheduled for handover in 2015.

Price-wise, ACL has benefited significantly from the protracted planning phase. The cost is much lower than would have been entailed if an order had been placed when the company started considering newbuilds four years ago. Quality control was a very important consideration in ACL’s choice of shipyard. QC practices at Hudong-Zhonghua, in conjunction with the yard’s track record, professionalism and willingness to embrace innovative ideas, won over both ACL and Grimaldi.

ACL’s weekly fixed-day North Atlantic schedule connects Hamburg, Gothenburg, Antwerp and Liverpool with Halifax, New York, Baltimore and Norfolk. The G4s may usher-in changes to the direct port call itinerary, and options under study include possibly dropping one or two of the current ports and taking in a southern US terminal.

In the latest issue of Grimaldi News, the parent group stated: “In summation, we are confident that these powerful new thoroughbreds will push ACL far up the league table of transatlantic shipping companies, while maintaining the healthy profit margins it has managed with the dray horses it employs today.” The focus on innovation, considers the Naples-based organisation, ultimately bears on an improved service offering to customers.

Principal particulars--ACL G4 class

Length oa (excluding stern ramp) c296.00m

Length bp 287.00m

Breadth, moulded 37.60m

Design draught 10.25m

Corresp. Deadweight 45,000t

Ro-ro capacity 28,900m²

Container capacity 3,800TEU

Propulsion power c 22,000kW (unconfirmed)

Service speed, 90% MCR, inc 15% sea margin 18 knots

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