M-class

Design, Construction, and Naming Notes

M-1 was a unique submarine, the only one of its class. All submarines up to this point, either Lake or EB designs, had been single hull boats, with all of the ballast tanks and fuel tanks internal to the pressure hull. In a double hull boat, the inner pressure hull was fully wrapped by an outer hull, and the space between the hulls was used for ballast and fuel tanks. The goal was to gain a lot of internal space that could be used for weapons, more powerful engines, and a larger crew. This design by Electric Boat was breaking new ground, as the only other double hull boat in USN service was the Italian Laurenti designed G-4. Because of the lack of experience in building this hull type, the results were not good. The tankage space was very tight and difficult to maintain, and the complicated venting and flooding arrangement made her very unstable when surfacing. She often took large lists until the tanks were fully emptied. M-1 had a short service life, only four years. No further double hulled boats were built for the USN until the T-class fleet submarines of 1920-1922. They were based on an expanded M-class hull and were equally unsuccessful. Double hull and partial double hull submarines were the way of the future, but advances in metallurgy and more experience in building this hull type was needed before it could be successful.

M-1 (Submarine No. 47, later SS-47)

Photo courtesy of the Submarine Force Library & Museum.

M-1 on the building ways at Fore River Shipbuilding, Quincy MA., October 1, 1914. The framework that surrounded her inner hull can be seen in the center, with the skeleton frames of her bow on the left. The circular frames are what the outer hull plating would be attached to at a later date. Her launching date was still 11 months in the future.

Photo courtesy of the Submarine Force Library & Museum.

This photo was taken on the same day as the one above, October 1, 1914. Details of M-1's frames can be seen. This view is from the bow looking aft.

Photo courtesy of the Submarine Force Library & Museum.

M-1 later in her construction phase, April 9, 1915. This view is from the bow looking aft. The mushroom shaped structure in the middle is the upper part of the tub for the retracting 3"/23 caliber Mk 9 gun that she would be later fitted with. The gun would retract vertically into this watertight tub, leaving only the end of the barrel above deck. The intention was to reduce underwater drag.

Photo courtesy of the Submarine Force Library & Museum.

M-1 on her launch day, September 14, 1915, Fore River Shipbuilding, Quincy MA. Both of the shutter doors for her port side torpedo tubes can be seen. At the tip of the bow is the squared-off towing fairlead (aka "bullnose"), and her bow planes are folded up alongside the superstructure. The men on deck are all Fore River and EB employees.

Photo courtesy of the Submarine Force Library & Museum.

M-1 afloat at last in Mill Cove off Quincy Bay, MA., September 14, 1915. She still has stern way on, but drag chains attached to the building slip will be quickly arresting her motion. A tug will tie up and move her to the fitting out pier to finish her construction. She was roughly 60% complete at this point.

National Archives Photo

M-1 is shown here on builder's trials, probably in Long Island Sound, early 1917. Outwardly she looked a lot like a bigger L-class boat, but she had a radically different hull type. She tended to be a wet boat on the surface, and she became dangerously unstable during the surfacing process.

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