Hai Shih-class (Guppy II)
Commissioned by Taiwan in 1973, the US-built *Hai Shih*-class submarine serves primarily in a training role and is distinguished by its World War II-era Tench-class hull.
| Subtype | Diesel-electric training submarine |
| Displacement | 1570 tons |
| Crew | 81 members |
| Width | 8.3 m (27.2 ft) |
| Length | 95.0 m (311.7 ft) |
| Propulsion | 4 × diesel engines driving electrical generators, 2 × 126-cell Sargo batteries, 2 × low-speed... |
| Range | 11000 km |
| Endurance | 75 days |
| Maximum speed | 20 knots |
- 1 or 2 x 5-inch (127 mm)/25 caliber deck guns
- 1 x 40mm Bofors gun
- 1 x twin 20mm Oerlikon mount
- 28 x torpedoes (or up to 56 mines)
Description
The submarine Hai Shih (S 791) was originally built for the United States Navy as the Tench-class vessel USS Cutlass (SS-473). Launched in 1944, the submarine belongs to a class developed as an improvement over the preceding Gato and Balao designs, featuring a stronger physical construction and a modified internal layout that converted a ballast tank to carry fuel for increased range.
The design of the class resolved a safety vulnerability present in earlier submarines by rearranging the main ballast tanks to remove internal vent riser pipes from the torpedo rooms. This change eliminated the risk of high-pressure pipe ruptures during depth charge attacks and freed internal space, allowing the vessel to carry additional torpedoes. The original diesel-electric propulsion system utilized diesel engines supplying direct-drive electric motors to turn two shafts, with lead-acid batteries providing submerged power.
Between 1947 and 1949, the submarine underwent a GUPPY II modernization. This configuration replaced the original batteries with more compact lead-acid units, increasing the total battery cell count to improve submerged power. The upgrade also added a snorkel, streamlined the sail and bow, upgraded the electric motors to double-armature types, and updated the electrical, air conditioning, sonar, fire-control, and electronic support measures systems.
The submarine entered Japanese waters for its first war patrol immediately after the August 1945 ceasefire. Following its post-war GUPPY II conversion, the vessel continued in United States Navy service until 1973, when it was transferred to the Republic of China Navy of Taiwan and renamed Hai Shih. The submarine remained active as of July 2021, representing the last operational World War II-era, US-built submarine in service with any navy. It is projected to remain in service until 2026. As of 2020, the class possessed the largest weapons load of any conventional submarine.