A 6-inch crack in the hull of the littoral combat ship USS Freedom caused the ship to abort sea-keeping trials on Feb. 12 and return to its homeport of San Diego for repairs, the U.S. Navy confirmed March 18.
The crack, about three and a half feet below the waterline in a weld seam between two steel plates in the hull, allowed water to enter a void space in the ship, according to Naval Sea Systems Command (NAVSEA). Flooding was contained, however, and, at a speed of about 8 knots, the vessel sailed about 600 miles to San Diego to begin repairs.
NAVSEA and Lockheed Martin, the ship's prime contractor, are reviewing the ship's design, construction drawings and welding procedures to determine what caused the hull crack. It is not yet clear, NAVSEA said, whether the problem is due to a design flaw or faulty construction techniques.
"Lockheed Martin is working closely with the Navy to confirm the root cause and have made all necessary repairs to the ship," Lockheed spokeswoman Kimberly Martinez said in a March 18 e-mail. "We are also supporting the Navy in additional testing along the hull to confirm this crack was an isolated anomaly."
The hull crack was first reported March 18 by Bloomberg News.
The crack appeared while the ship was performing heavy-weather sea trials off the northern California coast, said Cmdr. Jason Salata of Naval Surface Forces in San Diego.
A watch was kept on the space throughout the ship's return to San Diego, and the problem did not restrict the ship's maneuverability or speed, NAVSEA said. The 8-knot speed back to San Diego, Salata said, was based on fuel economy.
The horizontal crack measured just over 6 inches on the outside of the ship, and was about 3 inches long on the inside. It was amidships, at a point where the hull turns sharply inward.
Repairs to the hull were completed March 12 at San Diego after a cofferdam was built and installed around the crack. The hull repairs were made while the ship was undergoing a scheduled repair period.
A separate issue regarding hull cracks in the aluminum superstructure was dealt with during the repair period, NAVSEA said.
"Several small cracks" appeared aboard the ship last fall, NAVSEA said in a statement, correlating to predicted high-stress areas in the superstructure. Those areas had been "instrumented" before that time to detect problems, and "cracks were identified within the welds, indicating lack of fusion or weld defects."
Changes already have been made in the ship's design to correct the superstructure stress, metal fatigue and cracking, NAVSEA said, and many of those changes are being done in the current repair period.
USS Fort Worth (LCS 3), the next ship being built to the LCS 1 design, "had detail changes incorporated which mitigate these high stress areas," NAVSEA said.
The crack, about three and a half feet below the waterline in a weld seam between two steel plates in the hull, allowed water to enter a void space in the ship, according to Naval Sea Systems Command (NAVSEA). Flooding was contained, however, and, at a speed of about 8 knots, the vessel sailed about 600 miles to San Diego to begin repairs.
NAVSEA and Lockheed Martin, the ship's prime contractor, are reviewing the ship's design, construction drawings and welding procedures to determine what caused the hull crack. It is not yet clear, NAVSEA said, whether the problem is due to a design flaw or faulty construction techniques.
"Lockheed Martin is working closely with the Navy to confirm the root cause and have made all necessary repairs to the ship," Lockheed spokeswoman Kimberly Martinez said in a March 18 e-mail. "We are also supporting the Navy in additional testing along the hull to confirm this crack was an isolated anomaly."
The hull crack was first reported March 18 by Bloomberg News.
The crack appeared while the ship was performing heavy-weather sea trials off the northern California coast, said Cmdr. Jason Salata of Naval Surface Forces in San Diego.
A watch was kept on the space throughout the ship's return to San Diego, and the problem did not restrict the ship's maneuverability or speed, NAVSEA said. The 8-knot speed back to San Diego, Salata said, was based on fuel economy.
The horizontal crack measured just over 6 inches on the outside of the ship, and was about 3 inches long on the inside. It was amidships, at a point where the hull turns sharply inward.
Repairs to the hull were completed March 12 at San Diego after a cofferdam was built and installed around the crack. The hull repairs were made while the ship was undergoing a scheduled repair period.
A separate issue regarding hull cracks in the aluminum superstructure was dealt with during the repair period, NAVSEA said.
"Several small cracks" appeared aboard the ship last fall, NAVSEA said in a statement, correlating to predicted high-stress areas in the superstructure. Those areas had been "instrumented" before that time to detect problems, and "cracks were identified within the welds, indicating lack of fusion or weld defects."
Changes already have been made in the ship's design to correct the superstructure stress, metal fatigue and cracking, NAVSEA said, and many of those changes are being done in the current repair period.
USS Fort Worth (LCS 3), the next ship being built to the LCS 1 design, "had detail changes incorporated which mitigate these high stress areas," NAVSEA said.
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