The Cachalot-class submarines were a pair of medium-sized submarines of the United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 built under the tonnage limits of the London Naval Treaty

London Naval Treaty

The London Naval Treaty was an agreement between the United Kingdom, the Empire of Japan, France, Italy and the United States, signed on April 22, 1930, which regulated submarine warfare and limited naval shipbuilding. Ratifications were exchanged in London on October 27, 1930, and the treaty went...

 of 1930. They were originally given hull classification symbol

Hull classification symbol

The United States Navy, United States Coast Guard, and United States National Oceanic and Atmospheric Administration use hull classification symbols to identify their ship types and each individual ship within each type...

s V-8 and V-9 and so were known as "V-boat

V-boat

The V-boats were a group of nine United States Navy submarines built between World War I and World War II from 1919-1934. These were not a ship class in the usual sense of a series of nearly identical ships built from the same design, but shared authorization under the "fleet boat" program...

s" even though they were unrelated to the other seven submarines (V-1 through V-7) constructed between World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 and World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Joseph W. Paige of the Navy's Bureau of Construction and Repair

Bureau of Construction and Repair

The Bureau of Construction and Repair was the part of the United States Navy which from 1862 to 1940 was responsible for supervising the design, construction, conversion, procurement, maintenance, and repair of ships and other craft for the Navy...

 (BuC&R) developed the basic design, but the builder, Electric Boat

Electric boat

While a significant majority of water vessels are powered by diesel engines, with sail power and gasoline engines also remaining popular, boats powered by electricity have been used for over 120 years. Electric boats were very popular from the 1880s until the 1920s, when the internal combustion...

, was responsible for detailed arrangement; this was fairly bold, since EB had not built any new submarines since finishing four obsolescent boats for Peru.

Although externally much like the later "fleet submarines," internally the Cachalots were quite different. Due to pressure from the Submarine Officers Conference, they featured full double hulls adapted from the Kaiserliche Marine

Kaiserliche Marine

The Imperial German Navy was the German Navy created at the time of the formation of the German Empire. It existed between 1871 and 1919, growing out of the small Prussian Navy and Norddeutsche Bundesmarine, which primarily had the mission of coastal defense. Kaiser Wilhelm II greatly expanded...

's U-135, direct-drive diesel

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 propulsion systems, a separate crew's mess (reinstated thanks to EB's rearrangement of the internal layout; Portsmouth would follow soon after), and considerable space around the conning tower

Conning tower

A conning tower is a raised platform on a ship or submarine, often armored, from which an officer can con the vessel; i.e., give directions to the helmsman. It is usually located as high on the ship as practical, to give the conning team good visibility....

 within the large bridge fairwater (which was drastically cut down in World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 when the three-inch (76 mm) gun was relocated forward of the bridge). EB also relied on electric welding

Welding

Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...

, while Portsmouth clung to riveting; during the war, the riveted boats would leak fuel oil.

The external tanks proved too narrow for easy maintenance, and the MAN diesels were a constant headache, demanding re-engining in 1936. On the other hand, the class made a major contribution to habitability, when Cuttlefish was the first sub fitted with air conditioning

Air conditioning

An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...

, and to effectiveness, being first fitted with the Mark I Torpedo Data Computer

Torpedo Data Computer

The Torpedo Data Computer was an early electromechanical analog computer used for torpedo fire-control on American submarines during World War II . Britain, Germany, and Japan also developed automated torpedo fire control equipment, but none were as advanced as US Navy's TDC...

(TDC).

Size reduction had gone too far with the Cachalots, limiting their patrol endurance, and they were soon relegated to training.