Salmon - class submarine The United States Navy " Salmon " - class submarine s were an important developmental step in the design of the " Fleet Submarine " concept during the 1930s . An incremental improvement over the previous " Porpoise " - class , these rugged and dependable boats provided yeoman service during World War II , along with their immediate successors , the similar " Sargo " - class . Design . Authorized under the Fiscal Year 1936 provision of the Vinson - Trammel Act , two distinct , but very similar , designs were developed , to be built by three different constructors . The Electric Boat Company of Groton , Connecticut designed and built " Salmon " , " Seal " , and " Skipjack " ( SS - 182 to 184 ) . The Navy ' s lead submarine design entity , the Portsmouth Naval Shipyard of Kittery , Maine submitted a design for the Government group , which became " Snapper " and " Stingray " ( SS - 185 & 186 ) . Using the Portsmouth plans and acting as a follow yard , the Mare Island Naval Shipyard of Vallejo , California built " Sturgeon " ( SS - 187 ) . The two designs differed in minor details such as the locations of the access hatches for the forward engine room and crew ' s quarters , the shape of the horizontal conning tower cylinder , and , most significantly , the closure of the main induction valve . This difference led to casualties in " Snapper " and " Sturgeon " , and to the loss of " Squalus " . Larger than the design of the " Porpoise " - class , the conning tower installed by Electric Boat had two concave spherical ends , The Portsmouth design had a concave end aft and a convex one forward . Portsmouth and Mare Island ran into production difficulties with their conning towers , discovering cracks that caused the cylinder to fail the required pressure test . The problem was successfully fixed , but the experience caused the government yards to adopt the double concave design for the next several years . Externally , there were minor differences in the shape of the upper edge of the aft end of the conning tower fairwater . The Electric Boat design had a gradual downward taper to this bulwark , the Government design was slightly higher and straighter . Also , as built the Electric Boat trio had two 34 foot periscope s . This resulted in a fairly small periscope shear support structure above the fairwater . The three Government boats had one 34 foot and one 40 foot periscope and this necessitated a taller shear and support stanchion s . The Electric Boat - built " Porpoise " s had been built to an all - welded design . Conservative engineers and shipfitters at the Government yards stuck with tried and true riveting . Electric Boat ' s method proved superior , providing a stronger and tighter boat , as well as preventing leakage of fuel oil tanks after depth charge attacks . Finally convinced of the efficacy of Electric Boat ' s innovation , Government yards finally converted wholesale to welding for their three " Salmon " s and the Navy was entirely happy with the results . The six boats of this class were straight forward derivations of the later boats of the preceding " Porpoise " class . Although considered to be successful in most respects , valuable lessons had been learned from the " Porpoises " and operating experience showed the need to expand the operating envelope . The " Salmon " s were longer , heavier , and faster versions with a better internal arrangement and a heavier armament . Two additional torpedo tube s were added to the aft torpedo room , for a total of four forward and four aft . Some submariners wanted six tubes forward , but design philosophy and tactics of the day did not yet support this . However , in an effort to increase the number of torpedoes carried , four non - firing torpedo stowage tubes were installed in the superstructure below the main deck , stacked vertically , two each on either side of the conning tower . In order to access the weapons in these tubes , the boat had to surface and remove a portion of the decking on either side of the deck gun . Small boats stowed there for running sailors ashore for liberty were removed and set in the water . The weapons were extracted from the tubes one by one and winched up to the main deck . They were then placed on a raised loading skid and carefully lowered on an angle through a hatch into the forward torpedo room . This whole process took several hours to complete . The impracticality of spending several hours on the surface in enemy waters moving torpedoes below was lost on the designers . War experience led to the removal of these tubes during the boats ' first wartime overhauls . Two different main ( diesel ) engine types were installed in these boats during construction . The Government boats received a new model GM - Winton 16 - 248 V16 . Steady development work by GM - Winton had largely corrected earlier problems and this engine proved to be fairly reliable and rugged . The three Electric Boat units received a nine - cylinder version of the Hooven - Owens - Rentschler ( HOR ) double acting engine . This was based on a successful steam engine design . Having a power stroke in both directions of the piston , this engine promised nearly twice the horsepower in a size similar to a conventional in - line or V - type engine . Unfortunately , HOR encountered severe design and manufacturing difficulties converting the concept to internal combustion . They vibrated excessively due to imbalances in the combustion chambers . This broke engine mounts and caused difficulties in the drive train . Improper manufacturing of the gearing resulted in broken gear teeth . Reluctant to give up on the promise of the engine , the Navy coddled the HORs along until after the Pacific War began , when increased funding and operational needs caused these engines to be replaced with GM - Winton 16 - 278As during the boat ' s first wartime overhauls . Serious problems were encountered with the " Porpoise " - class all - electric drive . This drove the decision to radically alter the propulsion plant . The " Salmon " s were fitted with the so - called " composite drive " . In this arrangement , two main engines in the forward engine room drove generators in the fashion set by the " Porpoises " . In the after engine room , two side - by - side engines were clutched to reduction gears which sat forward of the engines . The propeller shafts led aft from each of the reduction gears , and were sited outboard of the engines . Two electric motors were mounted outboard of each shaft , connected directly to the reduction gears . For surfaced operation the engines were clutched in to the reduction gears and drove the propellers directly , with the generator engines providing additional voltage to the motors . For submerged operation , the direct drive engines were declutched from the reduction gears and the motors drove the shafts with electricity supplied by the batteries . Although proven to be satisfactory in operation , this unusual arrangement was quite cramped , making maintenance and repairs in the aft engine room somewhat difficult . All six of these submarines ( and all subsequent U . S . Navy submarines up to the late 1940s ) were built to a " partial - double hull " design . In this hull type , the inner pressure resisting hull is wrapped by an outer hydrodynamically smooth hull . The space between these two hulls is used for ballast and fuel tanks . The outer hull smoothly tapers into the pressure hull in the area of the forward and after torpedo room bulkheads , leaving the pressure hull exposed at the extreme ends of the boat . This is actually an advantage as it allows access to the pressure hull in these areas for maintenance . In a full double hull boat , the outer hull completely encompasses the pressure hull and the very narrow ends make it very hard to reach the pressure hull for repairs and maintenance . Commissioning and pre - war service . Portsmouth proved to be quite efficient in their production methods and they managed to complete and commission both " Snapper " and " Stingray " before Electric Boat delivered the lead boat " Salmon " for commissioning . In fact , all three of the Government built boats of this class beat their commercially built counterparts into service . After commissioning , these boats were very active in the fleet , operating initially with the Atlantic Fleet , conducting exercises in the Caribbean and around both sides of the Panama Canal . They transferred to the Pacific Fleet in late 1939 , homeported out of San Diego , commanded by Admiral Wilhelm L . Friedell . In October 1941 , as war clouds loomed on the horizon , the " Salmon " s were all transferred to the Asiatic Fleet as part of a belated effort to reinforce U . S . and Allied forces in the Philippines . They operated out of Cavite in Manila Bay until the war commenced . World War II . From the very start , the " Salmon " s were in the thick of the fight in the defense of the Philippines . The submarines of the Asiatic Fleet were the primary striking force available to Admiral Thomas C . Hart , the fleet ' s commander . He was assigned twelve " Salmon " s or " Sargo " s : " Sailfish " , " Salmon " , " Sargo " , " Saury " , " Sculpin " , " Seal " , " Skipjack " , " Snapper " , " Stingray " , " Sturgeon " , " Swordfish " . The qualities designed into the " Salmon " s for their role as fleet submarines made them well suited for the war they found themselves fighting , but some shortcomings came up that were not apparent prior to the war . It came to be realized that the boats were going to spend a lot more time on the surface than what had been previously acknowledged . Thus the large bulk of the conning tower fairwater became a liability . It was too easily spotted by keen - eyed Japanese lookouts using their excellent binoculars . It was found that portions of the fairwater plating could be cut away both fore and aft of the bridge , greatly reducing the silhouette . This also had the desirable effect of creating mounting locations for 20mm rapid fire cannon , which were useful against aircraft and small surface targets . The timely development of radar in the USN proved to be a key factor in the eventual victory over the Imperial Japanese Navy , and its incorporation into the " Salmon " s and other USN submarines gave them a critical advantage in detection and defense . The first sets became available within days of the war beginning , and they were introduced to the boats as they went into overhaul in 1942 . The original Mk . 21 3 " / 50 caliber deck gun proved to be too light in service . It lacked sufficient punch to finish off crippled or small targets quickly enough to suit the crews . It was replaced by the Mk . 9 4 " / 50 caliber gun in 1943 and 1944 . The well liked " Salmon " s were heavily relied on by the Submarine Force during the first two and a half years of the war , with some of them completing 15 war patrols before being assigned to training duties by 1945 .