Government boats had one 34 foot and one 40 foot periscope and this necessitated a taller shear and support stanchions. The Electric Boat-built Porpoises 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 Salmons 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 Salmons were longer, heavier, and faster versions with a better internal arrangement and a heavier armament. Two additional torpedo tubes were added to the aft torpedo room, for a total of four forward and four aft. The development of the Torpedo Data Computer, making broadside attacks practical, had made stern tubes more desirable. Some submariners wanted six tubes forward, but design philosophy and tactics of the day did not yet support this; additionally, for years the tonnage required to provide the extra tubes was over-estimated. 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