Slice delivers rig crew ready for work

The first examples of the ‘Slice’ hullform in the offshore industry, the crewboats Líder and Tenaz, are designed to offer a particularly stable, fuel efficient hullform with significant operational advantages and cost savings

Líder, the first Slice crewboat based on a design from Lockheed Martin in the US, was due to enter service in July with Hotelería y Servicios Petroleros SA de CV (HSP) in Mexico. The yard chosen by Lockheed Martin to build the new Slice crewboats, FBMA shipyard in the Philippines, launched Líder early in March, following the award to Lockheed Martin in 2004 of a contract to build two ships using the Slice concept.

The ‘Slice crew transport vessels’ (SCTVs), as they are known, will be operated by HSP in conjunction with Consultoría y Servicios Petroleros SA de CV (Cosepe), under contract to Mexico’s state-owned national oil company Petróleos Mexicanos (Pemex).

HSP has been awarded a contract to provide transportation services to Pemex for an initial five-year period, and the crewboats will be employed transporting workers and limited amounts of cargo from Ciudad del Carmen to the Campeche Basin oil field in the Gulf of Mexico, which is approximately 90 miles offshore.

Lockheed Martin first used the Slice hullform for a vessel it developed, built and tested for the United States Office of Naval Research (ONR). Derived from a ‘small waterplane area, twin hull’ (swath) hullform, the SCTV will, Lockheed Martin believes, improve operational efficiency and reduce Pemex’s operating costs, enabling Líder and Tenaz to operate in more challenging sea conditions, and still provide a safe, comfortable ride.

The Slice hullform has been proven to provide a high level of stability and speed in high sea states, the demonstrator built for the ONR being capable of in excess of 30 knots in wave heights of up to 12ft (Sea State 5).

The unique hullform has four separate underwater hulls that provide buoyancy, propulsion, and excellent hydrodynamic efficiency, the ship being controlled by a patented PC-based canard and stabiliser steering and motion control system. Such is the performance of the hullform that, according to Lockheed Martin, larger versions of the Slice hullform would be capable of 45 knots in Sea State 6 (13-20ft seas).

The key to the Slice hullform is reduction of wave-making drag, which is accomplished by the introduction of four short struts, four ‘teardrop’-shaped submerged hulls, and speeds that are well beyond the 'hump' on the Froude resistance curve.

“The key difference between the Slice and a swath is that with the Slice hullform it is possible to achieve a higher Froude number, because the displacement hulls are re-arranged into segments that have short lengths,” Rick Mattox, director of ship systems at Lockheed Martin explained.

Compared with vessels of equal displacement, Slice hulls are a quarter the length of a swath hull. The correspondingly larger diameter of Slice hulls provides the required displacement, and for the same operational speed the hullform doubles the Froude number.

According to literature released by Lockheed Martin, whilst a 500 ton swath operating at 25 knots would be near its wave resistance hump, a Slice of equal displacement would be operating well beyond the hump, and thus take advantage of substantially reduced wave resistance.

The improvements in the Slice hullform's resistance characteristics translate into several important benefits. Since the Slice is based on the swath, it possesses most of the swath's advantages, which include smaller size, better seakeeping and reduced acquisition and operating costs, but in addition, however, the Slice hullform is capable of higher speeds, has a reduced wake, better range, endurance and fuel consumption.

Other benefits highlighted by Lockheed Martin include a modular payload capability, simplified ‘payload balancing’, a large open deck, an unobstructed stern for loading and unloading, and the propulsors are located amidships – which reduces the likelihood of fouling and propeller damage.

Once in full operation in the Gulf of Mexico, Líder and Tenaz will transport 150 passengers to and from platforms in the Campeche Basin. “The key issue in the selection of the Slice for the SCTV requirement was the sea state and passenger comfort,” Mr Mattox told OSJ. “It was a big issue, because crew being transported to the platforms were showing up ill with seasickness, and were unable to start work when they should.

“We conducted an operational analysis which clearly demonstrated to HSV that the Slice was the best solution in terms of crew comfort, and in terms of operating costs. The requirement for these crewboats was a very difficult one – one that caused one of our principal competitors to drop out of the tender because it was too hard to meet with a conventional design. The only alternative would be to use helicopters to transport the men to the rigs, which would have been an order of magnitude more expensive”.

Naval and crewboat applications apart, Lockheed Martin is actively promoting other applications of the hullform, including patrol/interdiction, search and rescue, logistics/re-supply, oceanographic and hydrographic survey vessels, and any other roles that demand stability but also benefit from a high transit speed.

Other commercial applications include oil spill response, excursion vessels, yachts and recreation craft, all vessel types where there is a need for stability (both for operational reasons and passenger/crew comfort) and high speeds.

Lockheed Martin is, Mr Mattox explained, also pursuing tenders for more crewboats, for Petrobras in Brazil, along with tenders for a Belgian pilot boat, and is actively investigating how the Slice hullform might be applied to vessels used to support the growing number of offshore wind farms in Europe and elsewhere.

“Today, and even more so in the future, oil exploration and production demands support vessels to go farther from shore and into deeper waters, often exposing passengers to rougher seas and for longer periods of time,” said Carlos Alfaro, chief executive officer of HSP. “Líder and Tenaz will enable HSP to better serve Pemex by providing safer, more cost-effective, swifter and more comfortable transportation”.

Dave Broadbent, vice president and general manager of Lockheed Martin’s Littoral Ships & Systems, said: “We are extremely pleased to launch Líder. Not only are we on budget and on time for delivery later this year, but we are providing HSP with an innovative vessel that meets the demanding needs of the offshore industry. The faster, smoother ride of Líder and Tenaz will enable workers to arrive sooner, healthier and ready to work”.

Detailed engineering and construction work for Líder and Tenaz took place at Lockheed Martin in Baltimore, Maryland, and in Sunnyvale, California; at FBMA in Cebu, the Philippines; and in Southampton in the UK. OSJ