The Pacific War Online Encyclopedia
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| 1526 tons standard displacement
2410 tons submerged
|311'9" by 27'3" by 16'10"
95.0m by 8.3m by 4.9m
9 knots submerged
||to 300 feet
to 90 meters
| 6 21" (53cm) bow / 4 21" stern torpedo
tubes (24 torpedoes)
1 3"/50 AA gun
1 0.50 Browning machine gun
Up to 40 mines in place of torpedoes
||2-shaft diesel-electric (5400
shp surface, 2740 shp submerged)
|300 tons diesel oil|
| 11000 nautical miles (20,000km) at 10 knots surfaced
96 nautical miles (180 km) at 2 knots submerged
1942: Sides of cigarette deck cut down to reduce silhouette.
1943: Fairing around periscope shears removed and sheltered station forward of open bridge cut down to reduce silhouette. Some main ballast tanks converted to fuel ballast tanks to increase bunkerage by 50 tons. One of the periscopes was removed and replaced by a radar mast for SD radar on many units. The 0.50 Browning began to be replaced by a 20mm Oerlikon AA gun.
Late 1943: 3" guns replaced with 4"/50 guns on new construction and boats under refit.
1944: Radar was upgraded to SJ as this became
available. Light antiaircraft was upgraded to 1 or 2 40mm Bofors AA guns.
Late 1944: 4" guns begin to be replaced with a 5"/25 gun.
1945: 2 5" guns authorized with an improvised central director.
By the end of the war, the authorized sensor suite included SPR-1 radar warning receivers and SJ and SV radar. Improvements in machinery had raised the surfaced speed to 22 knots.
Some 24 boats were to be refitted as radar pickets
for the invasion of Japan, but the program became moot with the
Japanese surrender after two boats (Flying Fish and Finback) had been modified. The modifications included replacing one periscope with SV fighter direction radar and radio equipment.
The Gatos were just beginning to join the fleet at the start of the war. The last peacetime design, approved in November 1939, they closely resembled the Tambors, but their large engine rooms were subdivided by a pressure-proof bulkhead and their official maximum operating depth was increased to 300' (90 meters). They were a good design that was suitable for mass production, and they became the definitive U.S. submarine model of the Pacific War. They set new standards of habitability and endurance, had sophisticated fire control computers (by the standards of the day), and were heavily armed. These were all desirable qualities for a fleet submarine, meant to scout ahead of the battle line and do as much damage to the enemy battle line as possible prior to a decisive gunnery duel. Ironically, the Gatos would see very little action in this role, due to the eclipse of the battleship by the fleet carrier. They would be employed instead in the commerce raiding role.
With war looming, the Navy froze the design in 1940 and began focusing on making arrangements for mass production. Electric Boat Company, the usual private yard for submarine construction, was initially assigned sixteen boats, while the Navy's Portsmouth and Mare Island yards were assigned eight and four respectively. These were the first of a flood of construction orders that would eventually number 77 boats and require both the expansion of existing yards and the use of new yards. Portsmouth made extensive use of prefabrication to minimize time on its limited number of ways, setting a record of 56 days from laying down to launch of Cisco. The initial contract with Electric Boat included funds to double that yard's capacity, and later contracts funded the adjacent Victory Yard, which was owned by the government but operated by Electric Boat. Additional construction was assigned to Cramp Shipbuilding Company, Boston Navy Yard, and Manitowoc Shipbuilding Company, none of which had prior experience with submarine construction. The Cramp and Boston efforts did not work out well, but Manitowoc proved an unlikely success story. Located on a narrow river in Wisconsin, just off the Great Lakes, Manitowoc worked out a scheme for moving the boats by locks and canals to the Mississippi River and the open sea, and the Manitowoc boats acquired a solid reputation in the submarine service.
There was some friction between the Navy and Electric Boat
under the pressure of war. Electric Boat naturally focused on rapid,
economical mass production of basically sound boats, completing Corvina
in a record 317 days from laying down to commissioning. However, the
Navy demanded the constant addition of the latest improvements to the boats,
which worked against mass construction. It is perhaps
no surprise that, in the end, the Navy more or less got its way, though
most Electric Boat units spent some time in a Navy yard for last-minuted
alterations before being sent to the fleet.
The boats set a new standard for diving depth, which had been set at 250' (76 meters) since the construction of the Dolphin class.
The design bureaus concluded that the existing hull designs could
theoretically reach 500' (152 meters) without collapsing and were
certainly safe to 300' (90 meters), and it was only necessary to require
the hull fittings to meet the same standard to give the new boats a
design dive depth of 300'. The hulls were in fact virtually identical to
those of the Tambors.
Their chief faults were that they were not very maneuverable (having a turning radius of 150 yards or 137m submerged) and were slow to dive. The original conning towers were also quite high. Once war broke out, the conning towers were cut down considerably to reduce the silhouette of the boats. But the chief limitation of American submarines generally was not the submarines themselves, but the atrocious torpedoes they carried, which did not begin to approach acceptable performance until late 1943.
The gun armament proved more important than anticipated, and the 3" gun proved inadequate. However, during the design process, Captain Charles Lockwood had insisted on a gun foundation strong enough for a 5" gun, allowing many of these boats to be upgunned later in the war. The conning tower modifications consisted of removing the fairing around the periscope shears and cutting down the rear half of the conning tower in 1942, and cutting down the forward part of the conning tower in 1943. The latter modification created a platform for a second machine gun mount. Other improvements were made to reduce the dive time, such as cutting more openings in the superstructure to let air escape from under the weather deck more quickly and stowing the bow planes already angled for dive. These changes reduced dive times from 50 seconds when war broke out to less than 35 seconds by the time of the Japanese surrender. Camouflage was changed from pitch black to various shades of gray, which proved less visible at night in the tropics.
Twelve of the boats were ordered with H.O.R. engines, which
lived up to their dismal reputation for reliability. All were eventually
replaced with General Motors engines. General improvements in machinery
raised the average surface speed by about two knots by the end of the
Although the U.S. Navy carried out some experiments with a schnorkel, the ability of American submarines to operate at night against the Japanese was so great that the schnorkel was judged not worth the weight, space, and discomfort to the crews for any slight advantage it might confer, and none were fitted to any operational boats.
The basic Gato design was sound enough that the next class, the Balaos, were little more than Gatos constructed with thicker hull plates. In fact, the existence of the Balao
class was successfully kept secret by the Navy throughout the war, and
even the submarine force spoke of "thin-skinned" and "thick-skinned" Gatos. Improvements adopted by the Balaos were generally retrofitted to the Gatos as well, so that the two classes remained very similar throughout the war.
|Completed 1941-12-15 (Mare Island)|
|Completed 1942-1-30 (Mare Island)||Disappeared 1945-3-27 off Okinawa|
|Completed 1942-5-15 (Mare Island)||Sunk by depth charge 1943-10-11 in La Perouse Strait|
|Arrived 1942-6||Mined 1944-11-7 off Hokkaido|
|Arrived 1942-6-1||Sunk by depth charge 1944-11-8 south of Mindoro|
|Completed 1942-6-1 (Mare Island)|
|Arrived 1942-6-3||Disappeared 1942-7-30 in the Aleutians|
|Arrived 1942- 8||Disappeared 1943-2-16 in the Bismarcks|
|Completed 1942-9-1 (Mare Island)|
|Arrived 1943-1-1||Mined ca. 1943-7-4 off Hokkaido|
|Completed 1943-1-15 (Mare Island)|
|Completed 1943-2-15 (Mare Island)||Sunk 1944-3-27 by own defective torpedo|
|Arrived 1943-3-10||Disappeared 1945-4-20 east of Formosa|
|Arrived 1943-3-14 (Brisbane)|
|Arrived 1943-3-15||Mined ca. 1944-2-24 in East China Sea|
|Arrived 1943- 5||Sunk by depth charge 1944-8-24 west of Luzon|
|Completed 1943-7-15 (Mare Island)|
||Sunk by coastal batteries
1944-6-1 off Matsuwa
|Arrived 1943-8-21 (Brisbane)|
|Arrived 1943-8-30 (Brisbane)||Sunk by depth charge 1945-6-18 in Toyama Bay|
|Arrived 1943- 9||Torpedoed by I-176 1943-11-16 south of Truk|
|Arrived 1943-9 (Brisbane)|
|Arrived 1943-9-11 (Brisbane)|
|Arrived 1943-10 (Brisbane)||Disappeared 1943-12-2 off Makassar|
|Arrived 1943-10-2 (Brisbane)|
|Arrived 1943-10-11 (Brisbane)|
|Arrived 1943-10-16 (Brisbane)|
|Arrived 1943-10-30 (Brisbane)|
|Arrived 1943-11||Run aground 1944-10-25 in the Philippines|
|Arrived 1943-11||Mined 1944-7-26 east of Luzon|
|Arrived 1943-12||Mined 1944-8-13 north of the Phillipines|
|Arrived 1944- 6||Disappeared 1944-10-17 off Tsushima; likely mined|
The Pacific War Online Encyclopedia © 2007, 2009, 2012, 2013 by Kent G. Budge. Index
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