Hoisting submerged objects is always difficult, but when it’s a priceless Civil War relic that has been submerged for 136 years, difficult doesn’t begin to describe the process needed to make this lift!
The H. L. Hunley, a Confederate-made submarine, sank several vessels during the Civil War before it too sank in 1863 near Charleston, SC. In August 2000, it was raised using a 600 ton lattice boom crane mounted upon the jack barge Karlissa B.
The rigging was by far the most difficult part of the task. First, a steel frame was fabricated to encompass the length and breadth of the Hunley. Thirty-two nylon, web straps were hung from the frame running under the keel to support the full length of the submarine. Each strap was equipped with a bag filled with liquid foam which hardened it take the shape of the keel. All thirty-two straps had a dynamometer attached so as to measure and adjust the tension.
Hoisting the Hunley and frame without damaging it was no easy task either. With the barge secured to the sea floor by its jacks, providing a stable platform for the crane to operate, the Hunley was hoisted. The process was slow as it could only be hoisted a few inches at a time so its movement through the water would not crush it. Finally, the frame was laid softly and safely on the transport vessel that was being tossed by waves.
It was a very delicate process, but in the end, the Hunley made out safely and was taken to the LASH Conservation Center in the Old Charleston Navy Base where it was submerged during the archeological survey & excavation for twelve years. It is now located at Warren Lasch Conservation Center in North Charleston, SC.
Video Source: Published on Jan 9, 2013 National Geographic (2002)