Composite Ships: Building A New Paradigm
Departing from naval shipbuilding tradition, Northrop Grumman Ship Systems\' moving production line and modular-build strategies are ramping up production rates.
By Karen Fisher Mason, Contributing Writer | August 2005
In the 1990s, it took about 12 months to build a single composite-hulled, Osprey-class (MHC 51) minehunter at a Gulfport, Miss.-based facility then owned by Avondale Industries Inc. Outfitting and testing each of the four that were built (57.3m/188-ft-long vessels, with 907-metric tonne/893-ton displacement) required another 12 months. When Northrop Grumman Ship Systems (NGSS) acquired the site, "transformation" became the watchword when the company decided to use the facility to work simultaneously on four all-composite Coast Guard Fast Response Cutters (FRCs) and deliver four or five per year, while fabricating deckhouses, masts and other large composite structures for several additional programs. Although NGSS is currently under contract only to build the FRC prototype and the ship's current design dimensions could change (it's slightly smaller than the minehunter at 42.7m/140-ft long and 276 metric tonne/300-ton displacement), the shipbuilder has outfitted the facility to handle the fast-paced, full production contract for the ship in anticipation of its approval.
Source: Northrop Grumman
The Northrop Grumman Ship Systems' (NGSS) Composite Center of Excellence (Gulfport, Miss.) has been outfitted for simultaneous construction of four composite-hulled ships and several other large mari-time composite structures.
The facility's transformation coincides with a recent shift toward composite structures in naval applications. Prior to the current decade, composites saw limited military application on the seas, in part because their benefits were not fully understood, contends Dan Culleton, vice president of Gulfport operations for NGSS. He considers the most significant obstacle to have been "such a long heritage in steel construction, which is compatible with the paradigm for large ship construction." Minehunters were the obvious exception, made from composites especially because magnetic sea mines are triggered when a metal hull comes within range. Today, the benefits of greater stealth and reduced weight — especially above the water line, where reductions enhance stability — have prompted more composites applications. Equally important is the inherent corrosion resistance of these materials, which significantly lowers a ship's lifecycle costs. Major maritime programs with composites-intensive structures include the FRC, the U.S. Navy/Marine Corps San Antonio-class (LPD-17) amphibious transport dock ship and the U. S. Navy's DD(X) destroyer.
Source: Northrop Grumman
As many as five of these U.S. Coast Guard Fast Response Cutters will be constructed and outfitted annually by NGSS.
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Avondale launched its last composite minehunter in 1994 and became a division of Northrop Grumman Ship Systems in 2001. As production of the LPD-17 began in July 2000, the Gulfport facility geared up for fabrication of this vessel's two large composite masts. Soon the same facility will build the DD(X) composite deckhouse. The FRC, with its all-composite hull, decks and superstructure, will be produced entirely at the Gulfport facility, starting in early 2006. The cutters are part of the Coast Guard's Integrated Deepwater System (IDS), the contract for which was awarded to Integrated Coast Guard Systems (ICGS), a joint venture established by Northrop Grumman and Lockheed Martin. Although the final number is under review, the Coast Guard's initial plan called for 58 FRC hulls to be constructed under the IDS contract. To meet these imposing demands for composite structures, NGSS has expanded the Gulfport facility's dedicated composites area from 7,200m2 (78,000 ft2) to about 32,500m2 (278,000 ft2) of climate-controlled manufacturing space, with another 9,300m2 (100,000 ft2) planned for the DD(X) deckhouse work area. |
Source: Northrop Grumman
Shown in various stages of construction, this series of masts for San Antonio-class (LPD-17) amphibious transport dock ships are being constructed using NGSS' fully modular approach, which achieves production rates several times faster than those possible with traditional shipbuilding techniques.
But space for composite shipbuilding operations has been the easiest requirement to fulfill. With a vision "to be recognized as the production facility of choice for advanced composites ship construction," NGSS is co-locating research, design and manufacturing efforts at the facility, which it has named its Composite Center of Excellence. To expand its expertise in composites technology, NGSS has drawn upon personnel from composites-savvy sectors of Northrop Grumman. "We had a nucleus here," Culleton recalls, "and we asked folks from the aircraft side to join our design team. Putting them together has produced a great synergy." NGSS also has entered partnerships with other shipbuilders, such as Kockums AB (Malmö, Sweden), a builder of composite minehunters since 1974 and currently at work on carbon/vinyl ester Visby-class corvettes for the Royal Swedish Navy.
Source: Northrop Grumman
This 18.3m by 31.7m (60 ft by 104 ft) tool eliminates the need for - and the enormous cost of - many custom molds by enabling NGSS to build panels for bulkheads, decks and other components all on the same tool. The tool will be used across all NGSS shipbuilding programs.
The resulting operation will accomplish "rate production" — the target of four to five FRC cutters per year — not by building each ship in under three months, but by having multiple ships in various stages of production. NGSS will implement a strategy of modular fabrication and a moving production line. As a major part of this operation, NGSS is purchasing, in some cases modifying, and then installing technologies that are not uncommon in the composites industry — but on a scale of exceptional magnitude. Key transformation technologies are computerized resin mixing, laser placement, vertical infusion (to 12m/40 ft) and 5-axis NC cutting.
