The F-class submarines were a group of four submarines designed for the United States Navy by Electric Boat in 1909. F-1 and F-2 were built by Union Iron Works in San Francisco, while F-3 and F-4 were built by The Moran Company in Seattle, Washington. Design They were generally similar to the C-class and D-class submarines built by Electric Boat, but larger at 400 tons submerged vs. 337 tons for the D class. They were single-hulled boats with circular sections laid along the longitudinal axis. Overall length was and the beam was . The E-class and the F-class submarines were the first US submarines to have bow planes. Like the E class, their early-model diesels had problems and were replaced in 1915. The hull contained three compartments: torpedo room with four 18 inch (450 mm) torpedo tubes, control room with the ballast control valves, hydroplane controls and periscope engine room with two diesel engines The two diesel engines were clutched to shafts that turned electric motors that could also be used as generators for charging the batteries. The shafts also turned the screws. For submerged operation, the diesels were de-clutched and shut down, with the battery providing all of the submarine's power. The battery was an array of cells in rubber-lined, open-topped, steel jars. These vessels included some features intended to increase underwater speed that were standard on US submarines of this era, including a small sail and a rotating cap over the torpedo tube muzzles. For extended surface runs, the small sail was augmented with a temporary piping-and-canvas structure. Apparently the "crash dive" concept had not yet been thought of, as this would take considerable time to deploy and dismantle. This remained standard through the N class, commissioned 1917-1918. Experience in World War I showed that this was inadequate in the North Atlantic weather, and earlier submarines serving overseas in that war (E class through L class) had their bridge structures augmented with a "chariot" shield on the front of the bridge. However, as the F class served in the Pacific, they did not receive this upgrade. Starting with the N class, built with lessons learned from overseas experience, US submarines had bridges more suited to surfaced operations in rough weather. The streamlined, rotating torpedo tube muzzle cap eliminated the drag that muzzle holes would otherwise cause. In the stowed position, the submarine appears to have no torpedo tubes,