Editing Gato-class submarine (section)

===''Gato'' class===
The ''Gato''-class design, with a top range of 11,000 nautical miles (20,000&nbsp;km), was a near-duplicate of the preceding ''Tambor''- and ''Gar''-class ships. The only significant differences were an increase in diving depth from {{convert|250|ft|m}} to {{convert|300|ft|m}}, and an extra five feet in length to allow the addition of a watertight bulkhead dividing the one large engine room in two, with two [[diesel generator]]s in each room. The ''Gato''s, along with nearly all of the U.S. Navy fleet-type submarines of World War II, were of partial [[double-hulled]] construction. The inner pressure-resisting hull was wrapped by an outer, hydrodynamic hull. The voids between the two hulls provided space for fuel and ballast tanks. The outer hull merged with the pressure hull at both ends in the area of the [[torpedo]] room bulkheads, hence the "partial" double hull. Operational experience with earlier ships led the naval architects and engineers at the Navy's [[Bureau of Construction and Repair]] to believe that they had been unduly conservative in their estimates of hull strength. Without changing the construction or thickness of the pressure hull steel, they decided that the ''Gato''-class ships would be fully capable of routinely operating at 300 feet, a {{convert|50|foot|adj=on}} increase in test depth over the preceding classes.<ref>{{harvnb|Alden|1979|p=101}}</ref>

The ''Gato''s were slow divers when compared to some German and British designs, but that was mostly because the ''Gato''s were significantly larger ships. Sufficient fuel bunkerage to provide the range necessary for 75-day patrols from [[Hawaii]] to [[Japan]] and back could be obtained only with a larger ship, which would take longer to submerge than a smaller one. Acknowledging this limitation, the bureau designers incorporated a negative (sometimes called a "down express") tank into the design, which was flooded to provide a large amount of negative buoyancy at the start of the dive. Based on later wartime experience, the tank was normally kept full or nearly full at the surface, then emptied to a certain mark after the ship was submerged to restore neutral buoyancy. At the start of the war, these ships could go from fully surfaced to periscope depth in about 45–50 seconds. The superstructure that sat atop the pressure hull provided the main walking deck when the ship was surfaced and was free-flooding and full of water when the ship was submerged. When the dive began, the ship would "hang" for a few extra seconds while this superstructure filled with water. In an attempt to speed this process, additional limber, or free-flooding, holes were drilled and cut into the superstructure to allow it to flood faster. By midwar, these measures combined with improved crew training got dive times down to 30–35 seconds, very fast for such a large ship and acceptable to the ship's crew.<ref>{{harvnb|Alden|1979|p=88}}</ref>

The large size of these ships did negatively affect both surfaced and underwater maneuverability when compared to smaller submarines. No practical fix for this was available due to the limitations of the installed hydraulic systems used to move the rudder. Although a point of concern, the turning radius was still acceptable. After the war, a few fleet ships were fitted with an additional rudder topside at the very stern.<ref>{{harvnb|Friedman|1995|pp=210, 214}}</ref>

The class of ships had numerous crew comforts including showers, air conditioning, refrigerated storage for food, generous [[evaporator (marine)|freshwater distilling unit]]s, clothes washers, and bunks for nearly every crew member; these were luxuries virtually unheard of in other navies. The bureau designers felt that if a crew of 60–80 men were to be expected to conduct 75-day patrols in the warm waters of the Pacific, these types of features were vital to the health and efficiency of the crew. They could be added without impact to the ship's war fighting abilities due to the extra room of the big fleet ship. The air conditioning in particular had a very practical application, too, besides comfort. Should a submarine submerge for any length of time, the heat generated by the recently shut-down engines, electronic gear, and 70 warm bodies will quickly raise internal temperatures above {{convert|100|F}}. High humidity generated by tropical waters will quickly condense and begin dripping into equipment, eventually causing electrical shorts and fires. Air conditioning, acting mostly as a dehumidifier, virtually eliminates this problem and greatly increases mechanical and electrical reliability. It proved to be a key factor in the success of these ships during World War II.<ref>{{harvnb|Alden|1979|pp=48, 97}}</ref><ref>{{harvnb|Blair|2001|p=65}}</ref>

====Mine armament====
Like the previous Tambor/Gar classes, the Gato class could substitute mines in place of torpedoes. For the Mk 10 and Mk 12 type mines used in World War II, each torpedo could be replaced by as many as two mines, giving the submarine a true maximum capacity of 48 mines. However, doctrine was to retain at least four torpedoes on mine laying missions, which further limits the capacity to 40 mines, and this is often stated as the maximum in various publications. In practice during the war, submarines went out with at least 8 torpedoes, and the largest minefields laid were 32 mines. Post-war, the Mk 49 mine replaced the Mk 12, while the larger Mk 27 mine (in actuality an acoustic-homing torpedo) was also carried which only allowed one mine replacing one torpedo.<ref>[https://maritime.org/doc/mines-usn/index.php ORD696 Operational Characteristics of U.S. Naval Mines]</ref>

====Engine changes====
[[File:USS Cod, Engine Room, GM Cleveland Model 248 Engine.jpg|thumb|left|[[Electro-Motive Diesel|General Motors]] [[Cleveland Diesel Engine Division|Cleveland Model]] 16-248 diesel engine]]
[[File:Fairbanks Morse & Co. 38 8-1-8 diesel engine on the USS Silversides 2.jpg|thumb|left|[[Fairbanks-Morse]] Model 38D{{frac|8|1|8}} diesel engine]]

Twelve submarines of this class built by Electric Boat (SS-253 to SS-264) received what would be the final installations of the [[Hooven-Owens-Rentschler]] (H.O.R.) [[double-acting cylinder|double-acting]] [[diesel engine]]. The Navy had been tinkering with this engine off and on since 1937 because its unique design promised nearly twice the horsepower in a package the same size as other diesel engine types. Unfortunately, the Hooven-Owens-Rentschler company ran into severe design and manufacturing problems, and these engines proved to be operational and maintenance nightmares.<ref>{{harvnb|Friedman|1995|pp=263, 360–361}}</ref> Frequent breakdowns and utter unreliability had destroyed these engines' reputation with the Navy and they were all removed at the first opportunity and replaced by [[Electro-Motive Diesel|General Motors]] [[Cleveland Diesel Engine Division|Cleveland Model]]
16-278A V-type diesels. The other ''Gato''-class ships received either the [[Fairbanks-Morse]] [[Fairbanks Morse 38 8-1/8 diesel engine|38D 8-1/8]] nine-cylinder [[opposed-piston engine]] or the 
[[Electro-Motive Diesel|General Motors]] [[Cleveland Diesel Engine Division|Cleveland Model]] 16-248 V-type as original installations. These engines were hardy, rugged, and well liked by the crews and served the ships quite well.<ref>{{harvnb|Alden|1979|pp=90, 210–212}}</ref> Both the Fairbanks-Morse and General Motors engines were [[two-stroke cycle]] types.<ref>{{cite press release|last=Stern|first= Robert C. |date=2006|title=Gato-Class Submarines in action|url=https://quietwarriors.files.wordpress.com/2014/02/squadron-signal-4028-gato-class-submarines1.pdf|publisher= Squadron Signal Publications|access-date=2023-09-17}}</ref>

Two manufacturers supplied electric motors for the ''Gato'' class. [[Elliott Company]] motors were fitted primarily to boats with Fairbanks-Morse engines. [[General Electric]] motors were fitted primarily to boats with General Motors engines, but some Fairbanks-Morse boats received General Electric motors.<ref>{{Cite web|url=https://maritime.org/doc/fleetsub/elect/chap2.php/|title=Submarine Electrical Systems|website= www.maritime.org/}}</ref>

====Fairwater changes====
At the beginning of the war, ''Gato''-class ships, as well as the ''Gar'' and ''Tambor'' classes, had fully shrouded [[Fairwater (submarine)|fairwaters]] visually similar to modern nuclear submarines. Experience during the war led to the progressive reduction of this structure to reduce visibility and radar profile at the expense of underwater performance and foul-weather operating comfort. Most of the subs in postwar movies show the final result of these modifications. A side benefit of these modifications was the creation of convenient locations for antiaircraft guns.<ref name="Johnston 2019">{{harvnb|Johnston|2024}}</ref>