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Copper

Metal against mollusk

By Lynn Stanley

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This story has been updated for the July/August 2016 Top Webex issue.

Copper spotlighted in restoration of Old Ironsides

August 2015 - When it comes to the amount of metal the U.S. consumes, copper ranks third after iron and aluminum for its ductility, malleability, thermal and electrical conductivity and its antimicrobial properties. In 1758 Great Britain’s Royal Navy—also recognizing the trace mineral’s beneficial attributes—clad the bottoms of its warships with copper sheathing. It wasn’t to shield the wooden hulls from artillery, but to ward off the insidious onslaught of the Teredo navalis—commonly called shipworm. This species of mollusk, which plagued temperate and tropical waters, posed a higher threat to fleets on lengthy voyages from colder waters, but commanders may have been unaware of the danger lurking below the waterline. Today Teredo is found in oceans worldwide and remains notorious for its specialty: boring into and eating away a wooden ship’s hull. 

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A warship is born

On March 27, 1794 President George Washington signed the Naval Armament Act, thus creating the United States Navy. Taking a lesson from the Royal Navy, its six frigates were copper bottomed. Paul Revere had to requisition the rolled copper sheathing from England since it was not yet manufactured in America. 

The USS Constitution, one of the Navy’s original six, launched from Edmund Hartt’s shipyard in Boston. She earned the nickname “Old Ironsides” when she defeated the Royal Navy’s HMS Guerriere during the War of 1812. The USS Constitution maintained a perfect battle record and today is the oldest commissioned warship afloat in the world. Regular repairs and restorations have preserved one of history’s most important icons for more than 200 years.

In May 2015 the venerable frigate entered Dry Dock 1 in the Charlestown Navy Yard for a 2.5 year renovation. Restoration work will include replacing select deck beams, lower hull planking and caulking, and overhauling and repairing the ship’s rigging, upper masts and yards. Below the ship’s waterline, the hull’s nearly 20-year-old copper sheathing will be removed and replaced with 3,400 sheets of new copper.

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View of USS Constitution from within Dry Dock 1, May 29, 2015. [Courtesy USS Constitution Museum]

“Two hundred years ago a lighter weight copper sheathing was applied midship while heavier weight sheathing was used to cover high wear areas like the bow and stern,” says Margherita Desy, historian for the Naval History & Heritage Command Detachment Boston, which performs the restoration work. “Today the copper sheets are used to cover the entire lower hull and weigh 6 pounds each. While copper was an expensive material 200 years ago and is still expensive today, it has helped preserve ‘Old Ironsides’ for 217 years.”

The Constitution last dry docked in 1992. “For that restoration project we had to cut the copper sheets to size using a treadle-powered World War II-era slitting machine that had enormous counter balances,” recalls Desy. 

Ship shape

Sheets of 14 in. by 48 in. copper have been sourced pre-cut to size for the current restoration. The Detachment Boston restoration team will pre-punch each sheet with an 1852-patented, manually operated punch machine to set the nail holes. The Constitution’s white oak planks are caulked with cotton batting and oakum—hemp impregnated with tar. Traditionally, hull seams would be finished with tar, but restorers today use a rubberized marine sealant. Thirty hull planks below the waterline will be replaced. Once the new planks are installed, the hull will be painted and then overlaid with Irish felt prior to installation of the copper sheathing. 

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CDR Sean Kearns and USS Constitution Museum President Anne Grimes Rand remove the first sheet of copper for the ship, June 9, 2015. [Courtesy USS Constitution Museum]

“Each copper sheet is attached via the center holes first,” Desy explains. “The edges of the overlapping, like fish scales, are drilled through and then tacked with copper nails.” While the right materials are critical to keep Constitution ship shape, the unique skill sets of the staff performing the work are equally important.

When the Navy transitioned to steel hulls in the early 20th century, Desy says, “much of this artisan know-how for wooden ships was lost. For Constitution’s 1927 restoration, the Navy had to hire men from the shipyards of Bath, Maine. With a rebirth of interest in preservation and restoration of domestic architecture, wooden yachts and other structures, we’ve been fortunate to find men and women with a wide range of restoration talents. These skills are being taught again and it’s become a competitive marketplace to hire the Detachment Boston ship restorers.”

The $12 million to $15 million restoration of Constitution is expected to be completed in late 2017. America’s Ship of State will be then be returned to her berth in the Charlestown Navy Yard, to welcome visitors interested in learning about America’s naval heritage through this living portal to the past. FFJ

For updates on the 2015 restoration, visit www.usscm.org/restoration.

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