Photo courtesy of the Wisconsin Maritime Museum
The Wisconsin Maritime Museum is showing why drydocking a historic WWII submarine is essential.
Submarine Curator Karen Duvalle explained that a secret was discovered underneath one of the concrete blocks that the USS Cobia was sitting on after it was pulled out of the water, allowing the hull, or the underside of the boat, to be cleaned and repainted.
Duvalle says a welding seam near the keel of the ship was split entirely on one of the submarine’s ballast tanks.
The ballast tank has an opening at the bottom to allow water in and out for diving and surfacing, but a steel plate covered Cobia’s to prevent water from entering the tanks entirely.
When Cobia arrived at Fincantieri Bay Shipbuilding in Sturgeon Bay, all ballast tanks were pumped out if needed, but ballast tank two was not draining.
Duvalle believes the keel block held the steel plate in place, which is why they never noticed the issue in the first place. Two blocks will need to be removed one at a time to reweld the seam and keep the ballast tank empty.
An opening in the bottom of the sub may seem scary, but submarines have a double hull, and water only enters the ballast tank, not the hull itself.
The submarine left Manitowoc on September 7th and is scheduled to be away from the museum for about six weeks.
The Wisconsin Maritime Museum gave an early October return.
