by Edward C. Whitman Ph.D.
From their first appearance in mid-World War I, the Royal Navy’s K-class submarines were perhaps the most badly-conceived and ill-starred submersibles ever built by any nation. In both their original configuration and in the several derivatives that followed, the K-boats compiled an almost unbroken record of disaster and death, unredeemed by even a single instance of combat effectiveness. Spawned by a flawed tactical concept, implemented with immature and dangerous technologies, and kept at sea by the Admiralty’s stubborn refusal to admit the most obvious deficiencies, the K-class left in their wake a fascinating—even humorous—tale of operational and technical folly for which the query, “What were they thinking?” has seldom been more appropriate.
(Left) Commanding Officer of HMS K8 at the periscope in the Control Room. (Right) View of HMS K8 interior bow torpedo tubes.
Steam, Speed – and Surprises
By every measure of the time, they were prodigious submarines. At 339 feet long and displacing 1800 tons surfaced—2600 tons submerged—they were larger than a contemporary destroyer. Powered on the surface by two oil-fired boilers and a pair of steam turbines, which developed 10,500 horsepower and also charged lead-acid batteries, they were fitted with four electric motors to drive twin shafts while submerged. Admiral Fisher had also insisted on an auxiliary diesel engine, and it was to prove a lifesaver on many occasions. The K-class could make nine knots underwater, with a submerged endurance of approximately 80 nautical miles at two knots, and a maximum design depth of 150 feet. The ships were originally armed with ten 18-inch torpedo tubes: four in the bow, four mounted transversely amidships, and two above water in trainable mounts for surface attacks. There were also two four-inch deck guns and a three-incher on the superstructure.
However, the most distinctive features of the K-class derived directly from their steam power plants. Aft of the Control Room and the Beam Torpedo Rooms were located successively the Boiler, Turbine and Motor Rooms. Above the boilers were six large hull openings—two funnel uptakes and four air intakes, all closed by motor-operated valves. Each of the air intakes was 37 inches in diameter. The five-foot high funnels themselves protruded from a substantial superstructure aft of the conning tower and were tilted downward by electric motors and stowed in the superstructure prior to submerging. To dive the submarine, the boilers had to be shut down, the funnels retracted, and all the valves tightly seated to seal the Boiler Room while blowing ballast and converting over to electric drive. The residual heat was so fierce that the boiler spaces were totally uninhabitable during submergence, and had to be abandoned. A longitudinal passageway to one side thus had to be fitted to bypass the Boiler Room in moving between the two halves of the submarine. All the hatches, valves, hull penetrations, intakes, and uptakes necessitated by this Rube Goldberg arrangement led one experienced submariner to sum up the K-class boats with one pithy phrase: “Too many holes!” And on top of that, the biggest holes were located in a space that was normally unmanned while submerging.
The handling characteristics of the class, both on the surface and underwater, compounded their difficulties. Above water, the boats were insufficiently buoyant forward, and tended to plow into oncoming waves, shipping tons of water over the conning tower. The large, flat foredeck then tended to force the bow even deeper, as if the boat were teetering on the brink of a dive. Although the entire class was later fitted with a bulbous, free-flooding prow known as a “swan bow,” they were seldom able to operate at speed with the Battle Fleet in the North Sea except under the most favorable weather conditions. Both the forward deck gun and the superstructure torpedo tubes were unworkable and later removed. Even worse, the ships were easily—and regularly—pooped by following seas. Their overall wetness caused regular inundations of the Boiler Room through the funnels, extinguishing the fires and leaving the boats wallowing in the waves. With self-compensating fuel tanks open from below, seawater contamination of the fuel oil was also common, especially in rough weather, and caused frequent losses of power.
K-class handling was even more precarious in a dive. Because of their great length and weight, once they started down, they were hard to stop. Loss of depth control was common, and nosing into the bottom was a regular occurrence. Unless the submarine was very carefully trimmed, the hydroplanes and ballast tanks would frequently fail to correct her, particularly since the former were susceptible to unpredictable jamming. Fortunately, the K-boats operated mostly in the North Sea, where the water was shallow enough to keep them from exceeding their depth limits in the dive, but their erratic behavior made operating with surface ships a dangerous business.
Even if all went well in preparing the ship for diving, shutting down the steam plant, sealing the hull, and ballasting down, the K-class submarines could rarely submerge in less than five minutes, and attempting to accelerate the process only invited dangerous mishaps, like flooding or Boiler Room fires. K8 once succeeded in getting under in three minutes, 25 seconds, but a “crash dive” could not be said to have been part of their tactical repertoire.
However, to give credit where credit is due, the K-boats could indeed make 24 knots on the surface when the seas weren’t too rough, and their record was not exceeded by any other submarines until the advent of nuclear power.
Despite their enormous size, habitability aboard the K-class boats was relatively poor. Although the officers had fairly capacious accommodations—and even a small bathtub—the crew’s quarters were cramped and poorly ventilated. Lingering heat from the boilers kept the interior at a stifling temperature, and the humidity was oppressive. To make matters worse, the Admiralty—in perpetuating the myth that the K-class submarines were self-contained, independent warships—required the crew to live aboard, even in port. These wretched living conditions, coupled with a growing reputation for crew lethality, made the K-class unpopular boats to serve in, and morale was a recurring problem.
Early War Experience
With Lord Fisher gone, the Admiralty authorized ten more K-class submarines in 1915 and then another seven the next year for a total of 21. Virtually all of these were ordered even before the earliest of the first batch, K3, was commissioned at the Vickers yard in August 1916.
K3’s sea trials had been memorable. During speed runs, her Boiler and Turbine Rooms became so hot that the hatches had to be left open, and a head sea cracked the conning tower windows. On an early test dive, with Prince George—the future King George VI—aboard as an observer, the boat lost trim and burrowed into the muddy sea-bed with her propellers thrashing the air above. It took 20 minutes to back her out and return to the surface. Then, in January 1917, on one of her first war patrols from the Grand Fleet’s main operating base at Scapa Flow in the Orkney Islands, she shipped a beam sea and took so much water down the funnels that her Boiler Room nearly filled up. Admiral Fisher’s auxiliary diesel engine brought her back to port.
The second of the class to be completed, K13, began her career with a tragic accident. On 29 January 1917, during what was supposed to be the final test dive of her acceptance trials in Gareloch, one or more of the 37-inch Boiler Room ventilators failed to close, and the entire submarine abaft the midships Torpedo Room flooded. Emergency procedures were unavailing, and K13 settled to the bottom in 60 feet of water, with 49 survivors trapped forward and 31 dead aft. A tortuous 50-hour rescue operation, in which the bow of the submarine was lifted to the surface and an escape hole cut through the pressure hull, succeeded in extricating the living. The ensuing inquiry resulted in some superficial changes: more thorough procedures for shutting hull openings, better training, restricting the number of civilians allowed aboard (since seven had been lost on K13), and finally, decreeing that no future submarine would bear the unlucky number “13.” Accordingly, after K13 was raised and refurbished, she was recommissioned in October 1917 as K22.
Funnels being lowered as HMS K22 prepares to submerge.