FROM IRON BOILER TO CONFEDERATE SECRET WEAPON
Crew members reported that on test runs, H.L. Hunley would surface so near enemy ships, they could hear Union sailors singing.
From a cylindrical iron boiler bound together by iron strips and rivets, the H.L. Hunley began to take shape. At each of the sub's tapered ends were water ballast tanks with a seacock open to the outside water. The H.L. Hunley crew could submerge their vessel by opening the seacock and filling the ballast tanks. With a hand pump they could eject water from the ballast tanks and raise the sub. By the light of a single candle, a mercury gauge located near the forward tank was used by the crew to verify their depth. Her 4,000 pound keel ensured they would travel through the water upright.
A hypothetical depth gauge.
The heavy hatch covers were fitted with water-tight rubber gaskets and could be locked from the inside. These hatches sat atop two conning towers and were positioned 16 feet 3 inches apart. Several small viewing ports were located on each conning tower.
On top of the sub sat an air box that never worked as designed. Also referred to as a snorkel box, this simple contraption had a hollow shaft running through it. The ends of the shaft were bent upward, forming four-foot snorkel tubes that were fitted with stopcocks so they could be closed when the sub dived below four feet. However, without rising to the surface to take on fresh air, the sub could still remain underwater for over two very long hours.
Illustration of a hatch
Once all crewmembers were inside the submarine and in their stations, there was barely enough room to move within the sub. Even getting in and out was a tight squeeze. The two hatchways, one fore and one aft, were cylindrical "manholes" whose openings measured just 14 inches by 15 3/4 inches. Entering the submarine was like trying to fit through the center of tire.
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