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| Construction Drawings for K-Class Submarines (Click on Image to Enlarge) |
At the Portsmouth dockyard, design studies began in 1912, in response to a requirement for a submersible vessel with the necessary speed, lethality and endurance to operate alongside the Royal Navy’s Grand Fleet. The details fell to the then director of naval construction, Sir Eustace d’Eyncourt (1868–1951), His vision was of a vessel of 1,700-tons displacement on the surface, 339 ft long, with a 29 ft beam and 11 ft draft, powered by engines developing at least 9,000 shaft horse power (shp). At the time the largest British submarine was the E-Class, 660-tons displacement and 15-knot speed, powered by two 1,600 shp diesels.
Engines, whether diesel or gasoline, were neither reliable enough nor powerful enough to consistently deliver the 25-knot surface speed; only oil-fired geared steam turbines could fill that bill. A steam-powered submarine seemed a ridiculous choice. Admiral Sir ‘Jacky’ Fisher (1841–1920), First Sea Lord (1900–10, 1914–15), disparagingly remarked that: "The most fatal error imaginable would be to put steam engines in submarines." He would likely have shelved the whole project if it had come upon his watch. Across the channel, the French had been working on steam-powered submarines since 1909, and in 1914 even had two under construction, but these boats were far smaller than d’Eynecourt’s and not capable of 25-knot speed.
The eventual machinery arrangement of the British vessels ended up as a compromise between a proposal by Vickers Shipbuilding and Engineering and that of d’Eyncourt. With two main turbine sets for surface cruising, up to 25 knots, the auxiliary diesel and four electric motors for running submerged at up to nine knots, the boats thus required seven propulsion units. The main purpose of the diesel engine was to speed up the diving process by changing to diesel-electric drive before diving and just after surfacing.
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| K22 in Dry Dock by Charles Pears |
Twin screws were driven by shafts extending right through the machinery space. Two steam turbines (high pressure and low pressure) were geared to the forward end of each shaft while, further aft, two electric propulsion motors were tandem-coupled and connected through a separate gearbox to their associated main shaft.
The 8-cylinder/800hp Vickers diesel engine, however, was not connected to either main shaft. Mounted between the main shafts and propulsion motors in the aftermost machinery space, the engine was coupled at its forward end to a DC generator. The main storage batteries were located well forward in the area beneath the conning tower.
The cross-compounded propulsion turbines developed 10,500 shp and were supplied with steam by a pair of Yarrow water-tube boilers installed immediately forward in a separate compartment: an extremely cramped space in which each three-drum boiler took up almost the whole of the elliptical inner hull.
The armament for the proposed boats was to be:
- Eight 4 × 18-inch (460 mm) torpedo tubes, in-hull mounted, four bow, two port beam, and two starboard beam,
- Two 4 x 18-inch (460 mm) torpedo tubes, swivel-mounted on the rear deck,
- 2 × 4 in (101.6 mm) naval guns,
- 1 × 3 in (76 mm) quick firer gun,
Actually longer and heavier in the water than an R-Class destroyer, these boats were difficult to handle, both on the surface and submerged. According to one commentator, the class combined the s"peed of a destroyer, the turning circle of a battlecruiser, and the bridge-control facilities of a picket boat."
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| Below Decks on a K-Class Submarine |
With a length of 339 ft and a maximum "safe: diving depth of 200 ft, a dive at any angle greater than 30° meant that the bow could actually exceed the safe depth while the stern was still sticking out of the water. In the final version, the beam was about 2 ½ ft. narrower and the draft about 10 feet deeper. An important feature of the boats was the double hull construction, which gave greater surface buoyancy and increased space within the pressure hull by carrying as much weight as possible outside it. The inner pressure hull was of elliptical section while the outer and lighter hull was more ship-shaped and contained all the water ballast space. When the vessel was operating normally on the surface, the distribution of the ballast made handling sluggish.
The first three boats had a flush deck with a slight sheer forward, which led to a tendency to "dive" into head seas, so the later boats were redesigned to overcome this alarming characteristic by the fitting of large "clipper" bows to break the seas. To compensate for the top-heaviness, they contained buoyancy tanks. The guns on the front had to be moved to the rear and the swivel mounted torpedo tubes had to be removed entirely to accommodate the placement of the guns. The low freeboard and short funnels meant that in rough weather there was a constant risk of seawater pouring down through the funnels and extinguishing the boiler fires. This happened on several occasions on sea trials, forcing the affected boats to have to use the auxiliary diesel power to get back to port. The engine room became very hot and even the addition of large exhaust fans failed to solve this problem. The steamy heat even scalded crew and the severe condensation caused short circuits. Due to the complexity of the machinery and weaponry, coupled with the poor handling, the boats required a compliment of 60 strong men to operate.
The biggest drawback proved to be the diving procedure. The specification required five minutes, and the boats could meet that IF the steam engine and boilers had been shut down for at least 30 minutes before the diving commenced. There were the funnels to drop and seal, the intake and exhaust ports to close—it was said that the boats had "too damn many holes" and even a minor obstruction or misalignment would produce a serious leak. "Crash dives" simply weren’t possible. The designers countered that the boats were intended to operate on the surface and would submerge only as a planned tactic. Given their armament they could stand and fight against many foes, and with their speed they could outrun them if things got pear-shaped.
As ultimately built, the new boats displaced 1,980 tons on the surface and 2,566 tons submerged. Eighteen boats were ordered from seven different yards, and were designated as the K-Class because they were bigger than the J-Class. The first of these was K3, sourced to Vickers at Barrow-in-Furness, completed in May 1916. The K1 boat, sourced to the Portsmouth Dockyard, was not completed until November 1916.
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| The K12 with Modified Bow to Improve Buoyancy |
The service record of the K-Class boats earned them these sobriquets: the Killer Class, the Kalamity Class, and the Katastrophe Class. Here is a summary of the most important events:
K3 inadvertently held the unofficial record for maximum diving depth (266 feet [81 m]), following an uncontrolled descent to the bottom of the Pentland Firth. The boat managed to surface despite spending an extended period below "crush depth."
K7 was the only K-Class boat to see active service, firing a torpedo that failed to detonate. Fortunately, her 25 knot speed enabled her to avoid retaliatory fire.
K3’s sea trials went badly wrong in December 1916. While the future King George VI was on board, control was lost during a test-dive in water 150 feet deep. The bow went down fast and actually became stuck in the sea bottom leaving the stern sticking out of the water. Fortunately, the crew managed to trim the stern and resurface in 20 minutes or so.
K13 sank on 19 January 1917 during a diving trial off of Gareloch when an air intake failed to close completely, causing the engine room to flood. Forty-eight men drowned, but the boat was salvaged, modified, and recommissioned as K22 in March 1917.
K16 and K12 were stranded on the bottom at Gareloch, but eventually they managed to surface.
K4 ran aground on Walney Island in January 1917 and remained stranded there for some time.
K1 had to be sunk by the gunfire of HMS Blonde in November 1917, after colliding with K4 off the Danish coast.
K4 and K17 were sunk and K14, K22, K6 and K7 were badly damaged on 31st January 1918. Ten K-Class boats were operating with two light cruisers on a night exercise off May Island in the outer Firth of Forth. Trouble began when the helm in K14 jammed to starboard, causing the boat to swung round and collide with K22. The two boats locked together, causing the light cruiser HMS Fearless to swerve and ram K17. While manoeuvring to avoid this collision, K4 was rammed first by K6, then by K7. A total of 105 officers and men died. This event is often facetiously called "The Battle of May Island."
K5 was lost for unknown reasons during a mock battle in the Bay of Biscay on 20 January 1921. Nothing further was heard of the boat following a signal that they were diving; wreckage was recovered later that day. It was concluded that K5 had exceeded the crush depth.
K15 survived an incident in May 1921 where water was taken in through the funnels, stalling the steam engines and causing the boat to settle by the stern. Quick reaction by the captain and crew prevented her from sinking.
K15 then sank at her mooring in Portsmouth on 25 June 1921. This was caused by hydraulic oil expanding in the hot weather and contracting overnight as the temperature dropped, resulting in a loss of pressure that opened the diving vents. As the boat submerged, it flooded. Since it was portside, all of the hatches were open.
Eleven of the remaining K-Class boats were scrapped between 1921 and 1926, while the last to be built, K26, served until 1931. Was Admiral Fisher right? Or was d’Eynecourt just ahead of his time? Today’s nuclear submarines are, you guessed it, propelled by steam turbines. Some can do 40 knots underwater.
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