In the zero visibility waters of Charleston Harbor, Navy archaeologists have turned to technology, ingenuity, and interagency cooperation to reveal information essential for the upcoming recovery of the Confederate submarine H.L. Hunleythe first submarine in history to successfully sink another warship in battle. In February 1864, H.L. Hunley successfully rammed an explosive into and sank the Union blockade ship USS Housatonic. In the same engagement, Hunley was also lost. Using custom built, cutting edge equipment, archaeologists and engineers have returned to the site to assess the structural integrity of the hull and to examine areas of the submarine not documented in 1996.
Research completed this summer on H. L. Hunleys victim, the Union blockader Housatonic suggested that Dixon and his crew may have scored a major hit in the area of the powder magazine, possibly detonating up to three tons of black powder. Project personnel were concerned that the resulting shockwave might have damaged areas of H. L. Hunleys hull not uncovered during the 1996 seasonan eventuality which would make the recovery of the submarine more difficult and costly. Additionally, conservation specialists and structural engineers needed to assess the effect of 135 years of corrosion on the metal of submarines hull. A short project, running from October 27 and finishing on November 9, has offered answers to these questions and laid the groundwork for a successful recovery.
A careful examination of portions of H. L. Hunleys starboard side, not documented in 1996, offers indications that the sub is in a good state of preservation. Feeling along the hull, archaeologists were unable to find any evidence of blast damage or hull rupture. Looking closely at the hull plates themselves, Dennis Donovan from Coastal Inspection Inc. of Chelsea, Massachusetts, an expert in the ultrasonic examination of ships hulls, worked closely with engineers to develop a custom ultrasonic transducer capable of measuring the thickness of civil war wrought iron to an accuracy of hundredths of an inch. Data produced suggests that the hull plating has corroded little since H. L. Hunley was lost in February 1864.
While simple touch and high technology have answered some questions, ingenuity has answered others. Because visibility in the muddy water was zero most of the time, H. L. Hunley project conservator Paul Mardikian acquired a dental molding putty manufactured by 3M to allow archaeologists to take detailed molds of the surface of the iron, the rivets, and the seams between the plates. The putty set underwater in three to five minutes and produced a finely detailed mold of portions of the subs hull. These molds produced details of rivet size, spacing and conditionanother piece in the puzzle of H. L. Hunleys construction and condition.
Finally, interagency cooperation, in the form of geological sampling undertaken by the US Army Corps of engineers is producing data which will allow engineers involved in the recovery to determine the best possible method to anchor support for H. L. Hunley securely to the ocean floor. During the lift from the bed of Charleston Harbor, H. L. Hunley will be rigidly cradled in a frame structure to minimize any stresses. Prior to the lift, however, this frame must be secured to the bottom. Corps of Engineers information will allow engineers to determine how deeply this structure must be anchored to ensure the submarines safety.
The recent project took place under the overall guidance of Dr. Robert Neyland, H. L. Hunley Project Manager from the Naval Historical Center in Washington, DC. Project leaders were archaeologist Dr. David Conlin and conservator Claire Peachey from the Naval Historical Center. Other team members were archaeologists Ralph Wilbanks of Diversified Wilbanks, Inc., and Harry Pecorelli of Brockington and Associates, Inc., Hunley conservator Paul Mardikian of the Hunley Research Center, and Steve Wright from Oceaneering Advanced technologies. Ultrasonic hull thickness measurements were taken by Dennis Donovan of Coastal Inspection Inc. The United States Army Corps of Engineers geological research vessel, Explorer, under the guidance of Captain Tony Maze was skillfully maneuvered to within inches for geological sampling. Corps of Engineers geologists Card Smith, Bob OKelly and Jim Biddle provided exceptional geological and logistical expertise. The fieldwork was sponsored by Friends of the Hunley, Inc., Warren F. Lasch, Chairman.
1 December 1999