Description
The D-class submarines were enlarged and iterative improvements over the preceding C class, and were the first American submarines armed with four torpedo tubes. They were built by the Fore River Shipbuilding Company of Quincy, Massachusetts, under a subcontract from the Electric Boat Company of Groton, Connecticut. They had a length of 134 feet 10 inches (41.1 m) overall, a beam of 13 feet 10 inches (4.2 m) and a mean draft of 12 feet 6 inches (3.8 m). They displaced 288 long tons (293 t) on the surface and 337 long tons (342 t) submerged. The D-class boats had a crew of 1 officer and 14 enlisted men. They had a diving depth of 200 feet (61.0 m). [1]
For surface running, they were powered by two 300- brake-horsepower (224 kW) Electric Boat/Craig [2] gasoline engines, each driving one propeller shaft. [3] When submerged each shaft was driven by a 130-horsepower (97 kW) electric motor. Two 60-cell batteries provided power when submerged. They could reach 13 knots (24 km/h; 15 mph) on the surface and 9.5 knots (17.6 km/h; 10.9 mph) underwater. On the surface, the boats had a range of 1,179 nautical miles (2,184 km; 1,357 mi) at 9.6 knots (17.8 km/h; 11.0 mph) and 24 nmi (44 km; 28 mi) at 8 knots (15 km/h; 9.2 mph) submerged. [1]
The boats were armed with four 18-inch (45.7 cm) torpedo tubes in the bow. They did not carry reloads for them. [3] They were the first U.S. submarines to have four forward torpedo tubes which became the norm until the Tambor class which joined the fleet in 1940.
These vessels included some features intended to increase underwater speed that were standard on U.S. submarines of this era, including a small sail and a rotating cap over the torpedo tube muzzles. For extended surface runs, the small sail was augmented with a temporary piping-and-canvas structure. This structure would be disassembled and taken below before diving. USN tactical doctrine of the time did not emphasize quick dives so this was not seen as a liability. [4]
These were the first USN submarines internally subdivided into compartments. D-1 and D-2 had four compartments (torpedo room, forward battery/berthing & control room, after battery/messing, and engine/motor room). D-3 was fitted with only two bulkheads leaving one large compartment in the middle that consisted of both battery wells and the control room. [5] On D-1 and D-2 the helm wheel was actually in the after battery compartment, as the placement of the aft control room bulkhead dictated this arrangement. [6]
By 1918, the U.S. involvement in World War I and the perceived need to have submarines to support the war effort prompted the USN to refit the rapidly obsolescing D-class submarines with diesel engines. NELSECO, Electric Boat's engine subsidiary, was fully committed in other submarine work and did not have the capacity. The Lyons-Atlas Engine Company was chosen as a sub-contractor and they built six copies of the NELSECO 120-V4FS engines at their Indianapolis plant. The re-engining took place at the Philadelphia Navy Yard but was not completed in full until 1919. The D-class boats became the earliest USN submarines to be equipped with diesel engines, although the E-class were the first to be built with them. [7]
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