The short U.S. Navy training film Submarine Salvage shows the process Navy salvage crews use to retrieve sunken submarines. USS Hoist ARS-40 is shown in operation in the film. The submarine shown being salvaged appears to be a WWII boat; the techniques shown probably would not work with a modern submarine due to the size of these vessels.
The film begins with a submarine sinking and the rescue of the ship’s survivors. Rescuing survivors is the only goal immediately following the sinking of a submarine. Once all survivors are rescued, the Navy’s next objective is salvaging the ship (02:23). Specialized equipment is used by salvage forces (02:45); however, depending on the operation, different equipment and methods are required for a successful salvage operation. Regardless of the various factors, three basic principles or steps are consistent for salvaging submarines: prepare a salvage plan, rig for lift, and execute lift. The first, prepare a salvage plan, includes evaluating the environment, choosing an appropriate lifting method, and determining the required lifting force. Officers gather information they need to formulate their salvage plan, operating out of the shipyard where the sunken submarine was built (03:41), giving them access to the engineering plans and other details of the ship. The ocean bottom is taken into account as the ocean environment is examined. Depth plays a role as to what divers can accomplish, and weather is also a factor that must be considered. Planners must also know the state of submarine, which comes from interviews with survivors and communication records from the ship. Shipyard managers assist the planners in what needs to be done to make the sub airtight, if possible. A diver is then sent down (06:24) to survey the ship and gather on-the-spot information, most importantly whether the hull is partially buried or not. This allows for planners to determine the lifting method. The different lifting methods are: patch and pump (07:41), pontooning (08:30), self-lift, and lift ship (08:55). Patch and pump is the most common, but it requires the most diver time. Pontooning is the only practical way to lift in deep waters (up to max depths of 300 feet). Lift ship is usually only performed in shallow water. Depth and time requirements determine which method should be used. Lifting force (09:57) involves taking into account displacement and mud suction to calculate the lifting force required to raise the sub. The salvage ship moves out to prepare to raise the sub (11:06). The second step is to rig the sub for lift by placing wires under the hull. Sometimes tunneling is required to accomplish this. Divers can also set wires via lancing. A chain sling (13:38) is used to cradle the sub during lift. Prior to the lift, the sub is made to accommodate as much self-lift as possible. Divers prepare by rehearsing each step and conducting every test necessary on a sister ship (15:40) so they will know exactly what to look for and do. The third step is executing the lift (16:56), which can be done by raising with pontoons, by liftship (stern lift or bellylift), or by self-lift. Pontoons are moved into the water in preparation for lift (17:08). The submarine is gradually lifted over several stages of lifting to shallower depths. Lifting ships, such as YHLCs (19:16), the Navy’s heavy lift ships, can be used to pick up a sub. This must be done in pairs, and can lift via a bellylift or a stern lift. The submarine is lifted to the surface (28:06) during the salvage operation using a pontoon lift. Though the Navy’s increase in submarines comes with an increase in accidental sinking, well-planned salvage operations make it possible to retrieve sunken submarines and minimize Navy losses.
USS Hoist (ARS-40) was a Bolster-class rescue and salvage ship acquired by the United States Navy during World War II. Its task was to come to the aid of stricken vessels. Hoist was launched 31 March 1945 by the Basalt Rock Company shipyard near Napa, California; sponsored by Mrs. William E. Howard; and commissioned 21 July 1945, Lt. Cmdr. R. M. Brunner in command.
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