S-10 through S-13 were in the second group of Government design S-boats constructed at the Portsmouth Navy Yard in Kittery, ME. As the Government design was being finalized and the first boats laid down, intelligence reports on German U-boats were received and studied by the Submarine Officer's Conference. They came away deeply impressed with the tactical advantages of the U-boats that had a stern torpedo tube. Accordingly, the design for S-10 to 13 (not yet laid down) was altered to incorporate a single stern 21-inch tube in addition to the four bow tubes. The aft most tiller room of the design was vastly altered and reduced in size, and the tube's breech end let into the design's large motor room. No separate aft torpedo room was provided. Space for two reload weapons was incorporated by carefully rearranging the motor room equipment. They were NOT lengthened. These four boats also incorporated the S-8 bow plane modification, having their bow planes on the outer hull below the waterline.
In addition, the somewhat unreliable performance of the NELSECO/MAN/BuEng diesels engines of the previous boats prompted the BuEng engineers to go back to the original MAN company drawings and they produced a copy directly from those plans at the New York Navy Yard in Brooklyn, eliminating the NELSECO middleman. These engines, while still not perfect, were vast improvements and were considered to be quite reliable.
S-10 getting underway from the Panama Canal Zone, likely from Coco Solo, April, 1933. She has the third iteration of sonar on her forward deck, with the T-shaped SC sonar topped by the ball-shaped JK passive sonar. The JK was actually a flat plate transducer, but it was covered by a hollow rubber ball that greatly reduced the water flow noise over the array, increasing the speed the boat could be moving while using the sonar.
Although it is not apparent in this photo, by this date S-10 was suffering from a severe corrosion problem in her outer structure, especially aft. The problem got so bad that in some places the steel was nearly paper thin. For this reason the S-10 was sent back to Philadelphia and laid up in reserve in 1936. She would not be repaired and would be decommissioned and scrapped later that same year.
A fine port side shot of the S-11, near Submarine Base Coco Solo, Panama, October 4, 1935. By the date of the photo, the S-11 had been repainted black in accordance with a Submarine Force wide change in the submarine paint scheme. She has incorporated changes in her topside arrangement mandated by the loss of the S-4 (SS-109) in 1927. These changes include an expanded seating surface on the torpedo room and motor room hatches than enabled the use of a McCann Rescue Chamber, and rescue marker buoys on the starboard side forward and at the aft end of the superstructure. Also, for a reason unknown, she has had the ammunition storage locker at the forward lower end of the conning tower fairwater removed, possibly due to a corrosion control issue. She has also received the updated SC/JK sonar array on the forward deck similar to the S-10 above.