Aluminum has been an integral part of shipbuilding for more than a century. Its structural strength and light weight make it ideal for replacing steel in ships' superstructures.
In a century's time, the average weight of ships has more than doubled, making the use of aluminum attractive to shipbuilders despite the cost of the metal, which can run as much as four times the cost of low-carbon steel. Now aluminum might be coming into its own as a material of choice for a new generation of U.S. Navy vessels designed to protect American interests around the world.
At roughly one-third the weight of steel, aluminum has long been used for the construction of lifeboats, motor launches, patrol boats, yachts, cabin cruisers and search-and-rescue vessels. Aluminum also has come into its own in the past quarter-century in the cruise ship industry, used for such structures as deckhouses, hatch covers, ladders, gangways, stack enclosures, bulkheads, fuel tanks, lifesaving equipment and deck plates.
With contemporary cruise ships exceeding 100,000 tons in gross weight, more than twice the weight of the White Star Line's RMS Titanic more than a century ago, naval architects and shipbuilders have turned to aluminum as a suitable replacement for steel without sacrificing strength. The faster a vessel and the more weight it can carry translates into a quicker return on investment, which has become one of the main selling points for the use of aluminum in shipbuilding in the 21st Century.
Less weight also means more speed. In 1895, a Scottish shipyard built a 190-foot-long aluminum gunboat for the Imperial Russian Navy that boasted a then-record speed of 32 knots. Later that year, the aluminum yacht Defender won the America's Cup. In more recent years, Australia, with thousands of miles of coastline, has pioneered the use of aluminum for high-speed ferries. The country has built as many as 85 fast ferries for use both in Australia and New Zealand and for export to Europe, North and South America and the Middle East.
In 1990, the shipyard of Australia's Incat Tasmania Pty Ltd. built the first all-aluminum fast ferry, a 242-foot catamaran with a speed of 39 knots. By 2010, Incat Tasmania was producing 365-foot fast ferries made of marine-grade aluminum that can carry as many as 1,000 passengers and more than 300 vehicles at speeds up to 40 knots. In the early 21st Century, Incat Tasmania began successfully bidding for aluminum transport vessels for both the U.S. Army and the U.S. Navy. Dubbed "wave piercers" by the media, the transport vessels are typically designed atop an aluminum catamaran hull and can deliver as many as 350 combat troops at a time, plus their equipment, at more than 40 knots.
In 2005, Austal Ltd.'s Benchijigua Express emerged as the world's largest aluminum vessel. The 417-foot ferry employed in the Canary Islands on the Tenerife to Gomera and Palma run can haul nearly 1,300 passengers and more than 340 vehicles at speeds of 40 knots.
Speed, strength and weight were all considerations when the U.S. Navy awarded bids in December for 20 Littoral Combat Ships (LCS)—littoral refers to the shallow water between low and high tide—capable of operating in shallow coastal waters. The first of a total of 55 LCS are expected to enter service between 2012 and 2020.
In what might be a first, the Navy split the initial contract between two shipbuilders. Lockheed Martin Corp., Bethesda, Md., in partnership with Italian shipbuilder Fincantieri Cantieri Navali Italiani SpA, will build 10 conventional steel mono-hull vessels at Bay Shipbuilding in Marinette, Wis., on Lake Michigan, while the other 10 will be built by Austal at its shipyards in Mobile, Ala. The Australian shipbuilder will build an aluminum trimaran LCS that one observer likened to a Klingon warship from Star Trek. The orders for the two vessels will provide thousands of jobs each in northern Wisconsin and coastal Alabama.
The hull and superstructure of the Austal version of the LCS will be marine-grade aluminum, while the superstructure of the Lockheed-Fincantieri version also will be marine-grade aluminum.
The LCS, able to operate in water as shallow as 20 feet, will be designed for interdicting everything from Somali pirates to Caribbean drug runners and North Korean patrol boats. Armed with 2-inch guns and short-range missiles, the 417-foot LCS is designed to operate at speeds of up to 50 knots, more than enough to chase down almost anything afloat anywhere in the world.
Critics, including Sen. John McCain (R., Ariz.), question why the Navy has obligated itself to two competing versions of the LCS. But the Navy counters that the competitive nature of the contract will allow it to save as much as $100 million on the cost of building each of the $600-million vessels. The Navy also says it will use the two designs to determine which will win the final contract for the rest of the 55-vessel fleet. BILL BECK