In August 1912, the US Navy authorized eight more "K" class boats, however, the design was altered in favor of stronger internal bulkheads. The Electric Boat L class submarines introduced the first strengthened internal bulkheads in submarines, which allowed the boats to dive to deeper depths. A 3-inch gun placed in a disappearing mount forward of the bridge was added; this being inspired by a German innovation. The L-boats introduced air purification to the submarine fleet. Stale air was blown over chemicals, and compressed oxygen was released into the submarine to supplement the interior atmosphere.
Electric Boat contracted these out for FY1914 but the argument was made that no further advances in speed and range could be made unless larger submarines were designed. In March 1913, Congress authorized eleven "L" class boats and an enlarged "M" class prototype. Laid down between March 1914 and February 1915, the 11 submarines of the L class were commissioned between April 1916 and February 1918. Seven were built by Electric Boat, three by the Lake Torpedo Boat Company, and one by the Portsmouth Naval Shipyard (to Lake's design). The last named - L-8 (SS-48) - was the first U.S. submarine constructed in a government yard.
Congress had authorized seven L-class coastal submarines for 1913, and three of them - L-5 through L-7 - had been assigned to Lake before his financial troubles materialized. Lake weathered the bankruptcy well enough to reorganize and resume operations by early 1914, when he started construction of L-5 at Bridgeport and subcontracted the other two boats to Craig Shipbuilding in Long Beach, California. All were completed and commissioned successfully by early 1918. In fiscal year 1914, the Portsmouth (New Hampshire) Naval Shipyard was assigned construction of L-8 to Lake's own L-class design, and she emerged in 1917 as the first submarine built by the Navy itself.
They were slightly larger than their "K" class predecessors. L-1 thru 4 were powered by the same two Nelseco 450hp diesel engines as the K-class, L-5 onward had more powerful Busch Sulzer 600hp diesel engines. The increased engine output balanced the increased displacement for roughly even speed when compared with the "K" class. Test depth was 200 feet.
Intended primarily for coastal defense, the L-class boats displaced 450 tons surfaced and 548 tons submerged on a length of 168 feet. With two 450-horsepower diesel engines (600-horsepower Busch-Sulzers on the Lake version), they could make 14 knots on the surface and 10-1/2 knots submerged, with endurance of 3,150 nautical miles at 11 knots. Underwater endurance was 25 miles at 8-1/2 knots. The submarines were armed with four 18-inch torpedo tubes (in the bow) and were the first to carry a deck gun - a 3-inch/23-caliber disappearing mount just forward of the bridge. When stowed, only the gun barrel projected vertically, but reportedly this cost them a half-knot in underwater speed. The complement was 28 officers and enlisted men.
They performed patrol duties during World War One. Early submarine classes such as E, H, K, L, M, N, O, and R, known as "pig boats" or "boats" because of their unusual hull shape and foul living conditions, ranged in displacement from 287 to 510 tons. The fastest "boats" achieved top surface speeds of 14 knots under diesel power. During World War I, US submarines were divided into two groups according to mission. Boats of the N and O classes, as well as some of the E type, patrolled American coasts and harbors in a defensive role. Some K, L, O, and E class boats conducted offensive, open-sea operations from the Azores and Bantry Bay in Ireland. They supported the Allied effort to maintain open sea lanes along the European coast and in the approaches to the British Isles.
The L-boats of SUBDIV 5 - plus E-1 - left Newport, Rhode Island for Europe in early December 1917 under tow by Bushnell and two ocean-going tugs. Bound for Ponta Delgada in the Azores, the group ran headlong into a hurricane and was forced to divert toward Bermuda. Although the flotilla was badly scattered, with one tug and a submarine actually returning to Boston, the other tug and four submarines eventually reached their destination. Then, after several more straggled in, Bushnell, a tug, and four submarines completed the remaining 1,000 miles to Bantry Bay on 27 January 1918, with three more boats to follow. They were promptly re-designated the "AL" class to avoid confusion with British L-class submarines and under the tutelage of the Royal Navy, began preparing for their role in the ASW effort off southern Ireland.
On average for much of 1918, three of the seven U.S. submarines would be at sea on eight-day patrols, while the others were enjoying refit periods in port. The basic patrol tactic was to cruise at periscope depth during the day, searching the assigned area for German submarines transiting on the surface and then to come up at night to recharge batteries. The record shows a total of 21 claimed enemy sightings, of which four led to torpedo attacks, none successful.
Late in World War I, the seven U.S. L-class submarines of SUBDIV 5 were transferred to Bantry Bay, Ireland to carry out anti-submarine patrols in an area of responsibility that included St. George's Channel and the western approaches to the English Channel. Several American battleships were also stationed at Bantry Bay, and an entire division of them formed the 6th Battle Squadron of the British Grand Fleet at Scapa Flow in the Orkney Islands.
They were decommissioned between April 1922 and November 1923. L-8 was used as a target for the magnetic exploder in 1923 and rests three miles south of Brenton Reef Light, outside of Narrangansett Bay, Rhode Island. Three were sold for scrap in 1922, three in 1925, and four in 1933.
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