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USS Tench (SS-417)

Diesel-Electric Attack Submarine

United States | 1944

"The Tench-class of diesel-electric-powered attack submarines was headed by USS Tench SS-417 herself and proved of great value to the USN in WW2."

Authored By: Staff Writer | Last Edited: 01/18/2018 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site; No A.I. was used in the generation of this content.
The United States Navy (USN) in World War 2 (1939-1945) relied on three major classes of diesel-electric attack submarine - the Gato-class, the Balao-class and the Tench-class (in order). The Gato-class saw construction begin prior to the American involvement in the conflict in 1940 and seventy-seven boats were completed to the standard. The Balao-class added an impressive one hundred twenty from 1942 until 1946 and proved the most numerous of the USN undersea fleet. The Tench-class was born as an improvement over the previous two classes and numbered twenty-nine boats before the end - some fifty-one were cancelled due to the end of the war.

Culmination of a Years-Long Process
The Tench-class was able to utilize years of wartime data in its design and directly succeeded the Balao-class boats. Production began in earnest in 1944 and would last until 1951. The class was notable for its increased operational range (reaching 16,000 nautical miles from the original 11,000 nm) and hull strength, tested down to 400 feet (surpassing 300ft of earlier boats). In essence, it was the culmination of American boat design during the war that began back with the old P-class ("Porpoise") boats of the mid-1930s.

Propulsion Arrangement
As with the other two classes, the Tench-class relied on a diesel-electric propulsion scheme which involved marine diesel units for surface running and electric motors tied to battery packs for undersea travel. Four diesels were used for the former and two low-speed direct-drive electrical generators (tied to 2 x 126-cell Sargo battery packs) powered the boat in the latter. This arrangement supplied 5,400 horsepower when surfaced and 2,740 horsepower when submerged and drove a pair of screws at the stern. Surfaced speeds could reach just over 20 knots while undersea travel was limited to 8.75 knots.

The Tench-class improved the machinery some by utilizing a directly-coupled, slow-turning motor and worked better within the confined spaces of the boat's lines. The fuel and ballast areas were also refined for better volume and balance as well as to reduce the risk of flooding and being detected by enemy Anti-Submarine Warfare (ASW) equipment. Diving times were also improved over previous types.

Aboard was a team of eighty-one made up of a mix of officer and enlisted personnel. Onboard stores supplied the crew for up to seventy-five days. Armament was the usual mix of bow- and aft-facing torpedo tubes and deck guns. Ten total 21" torpedo tubes were installed with six at the nose and the remaining four at the tail. Twenty-eight reloads were carried - four extra than the Balao-class due to the revised internal spacing arrangement. On the surface, the boat was armed with the typical 5" (127mm) /25 caliber deck gun on a trainable mounting. This was used against surface targets as needed. Close-in defense was handled by 40mm Bofors and 20mm Oerlikon Anti-Aircraft (AA) weapons - also on trainable mountings. The Tench was outfitted with a Fire Control (FC) computer system as well as radar.

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Tench-class and Balao-class
Of relatively all-new design with good endurance and solid firepower, the Tench-class was a force to be reckoned with. Externally they strongly mimicked the lines of the Balao-class and, indeed, the close relationship between the two types was driven home as some of the changes instituted in the Tench design were also brought along in some of the Balao-class boats.

Construction and Activation for Service
USS Tench (SS-417), serving as the lead ship of the group, saw her keel laid down on April 1st, 1944 at the Portsmouth Navy Yard and was launched to sea for evaluation on July 7th of that year. She was commissioned as soon as October 6th, also that same year. Trials were held outside of New London (Connecticut) and Tench took the usual route (by way of the Panama Canal) to the Pacific - heading for the USN base at Pearl Harbor, Hawaii - during December.

Wartime Service
Tench would go on to complete three total war patrols due to her late entry into the war. The lateness of the class meant that barely a dozen or so of the boats were actually available for wartime service - many were still in the process of construction, being fitted out or in trials when the war came to a close. However, none would be lost to accident or enemy action as a result.

Her first patrol took her to the East China Sea and the Yellow Sea and ended in April of1945. A refit followed before the second patrol began in May where the boat was active in Japanese homeland waters. Mikamisan Maru was torpedoed and sunk in June and Ryujin Maru followed days later. On June 9th, the freighter Kamishika Maru - Tench's biggest war prize - was sent under. One of her own torpedoes, having entered an uncontrolled circle, threatened the boat but Tench was able to evade before finding peace at Midway.

The third war patrol proved to be her last when she went into action once more - this in late-July. The Empire of Japan surrendered on August 15th, 1945 to officially end World War 2. In March of 1946, Tench was placed in reserve, having journeyed back to the American East Coast (New London). For her relatively short combat service in the Grand Conflict, USS Tench was the recipient of three Battle Stars.

GUPPY Conversion Program
Tench was then modernized through the GUPPY program which made good use of captured German U-boat technology and design philosophy as it related to the ground-breaking Type XXI series (detailed elsewhere on this site). The work made for a more effective attack platform surrounding her performance, particularly when submerged. She was recommissioned for USN service in January of 1950.

Post-War Career
In this new guise, Tench operated for twenty more years while undertaking various patrolling actions in Atlantic waters and, later, the Mediterranean Sea - the primary threat of the day was now the Soviet Union. In late-1968, she participated in Operation Silvertower in Atlantic waters as part of a NATO exercise. In October of 1969, she was reclassified with the hull designator of AGSS-417 to mark her as a "General Auxiliary Submarine" amidst the rise of newer and more powerful Navy attack types.

In May of 1970, she was once again placed in reserve status and remained as such until August of 1973 to which point her name was struck from the Naval Register and her hull stripped of its military value. She was then sold for scrap.

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Power & Performance
Those special qualities that separate one sea-going vessel design from another. Performance specifications presented assume optimal operating conditions for USS Tench (SS-417).
As Built: 4 x Fairbanks-Morse Model 38D8 10-cylinder opposed diesel engines with electrical generators developing 5,400 horsepower; 2 x 126-cell Sargo battery packs; 2 x General Electric electric motors delivering 2,740 horsepower.
20.3 kts
23.3 mph
Surface Speed
8.8 kts
10.1 mph
Submerged Speed
10,002 nm
11,510 miles | 18,524 km
The bow-to-stern, port-to-starboard physical qualities of USS Tench (SS-417).
311.7 ft
95.01 meters
O/A Length
27.3 ft
8.32 meters
17.0 ft
5.18 meters
Displacement (Submerged)
Available supported armament and special-mission equipment featured in the design of USS Tench (SS-417).
As Built:
6 x 21" (533mm) torpedo tubes in the bow.
4 x 21" (533mm) torpedo tubes in the stern.
24 x Torpedo reloads.
1 x 5" (130mm) /25 caliber deck gun.
1 x 40mm Bofors Anti-Aircraft (AA) gun.
2 x .50 cal (12.7mm) Browning M2 Heavy Machine Guns (HMGs) (for AA defense).
Ships-in-Class (29)
Notable series variants as part of the USS Tench (SS-417) family line as relating to the Tench-class group.
USS Tench (SS-417); USS Thornback (SS-418); USS Tigrone (SS-419); USS Tirante (SS-420); USS Trutta (SS-421); USS Toro (SS-422); USS Torsk (SS-423); USS Quillback (SS-424); USS Corsair (SS-435); USS Argonaut (SS-475); USS Runner (SS-476); USS Conger (SS-477); USS Cutlass (SS-478); USS Diablo (SS-479); USS Medregal (SS-480); USS Requin (SS-481); USS Irex (SS-482); USS Sea Leopard (SS-483); USS Odax (SS-484); USS Sirago (SS-485); USS Pomodon (SS-486); USS Remora (SS-487); USS Sarda (SS-488); USS Spinax (SS-489); USS Volador (SS-490); USS Amberjack (SS-522); USS Grampus (SS-523); USS Pickerel (SS-524); USS Grenadier (SS-525); USS Unicorn (SS-436); USS Walrus (SS-437); USS Pompano (SS-491); USS Grayling (SS-492); USS Needlefish (SS-493); USS Sculpin (SS-494); SS-495 through SS-515; USS Wahoo (SS-437); SS-517; USS Wahoo (SS-518); SS-519 through SS-521; USS Dorado (); USS Comber (); USS Sea Panther (); USS Tiburon (); SS-537 through SS-562; SS-551 through SS-562
Global operator(s) of the USS Tench (SS-417). Nations are displayed by flag, each linked to their respective national naval warfare listing.
National flag of the United States

[ United States (retired) ]
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Image of the USS Tench (SS-417)
Image from the archives of the United States Navy; Public Domain.

Mission Roles
Some designs are single-minded in their approach while others offer a more versatile solution to seaborne requirements.
Some designs stand the test of time while others are doomed to never advance beyond the drawing board; let history be their judge.
Going Further...
USS Tench (SS-417) Diesel-Electric Attack Submarine appears in the following collections:
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