It’s always been a risky business riding submarines.

Since man decided to try and conquer the underwater kingdom of Neptune, there has always been an element of risk. Every nation has stories of boats that were sent out on missions that did not come back. Great Britain’s Royal Navy is no exception. Even from the beginning, they shared in their ability to succeed and fail under the water.

The K Class submarine is one of those learning lessons that left an impact on many nations. The early boats of all Navies struggled with the balance between propulsion and safety. The advent of the diesel engine had just begun in the early 1900’s and some nations were still trying to use the most common of the propulsive methods known (besides sails). That would be steam.

The tricky part about steam is that it requires a source of heat. That would come from a boiler that required an external source of fuel to develop a sufficient amount of steam to make the boat’s turbine engines move. Steam had been around since the middle of the previous century on board ships and year over year technical advances made it more efficient.

In 1913 an outline design was prepared for a new submarine class which could operate with the fleet, sweeping ahead of it in a fleet action. At that time the only way which they could have sufficient surface speed, of 24 knots (44 km/h), to keep up with fleet was to be steam powered. In a fleet action, the submarines would get around the back of the enemy fleet and ambush it as it retreated.

The boats were to be 338 ft. long and displace 1,700 tons on the surface. The design was not to proceed until results from trials of HMS Nautilus and Swordfish had taken place. After the trials, the slightly smaller three-screw submarine, the J class, was designed. By the middle of 1915 it was clear that the J class would not meet expectations, in particular they would only reach 19 knots – less than the 21 knots needed to accompany the fleet.

The K class design was resurrected and 21 boats ordered in August at a cost of £340,000 each. Only 17 were constructed, the orders for the last four being cancelled and replaced by orders for the M class.

Six improved versions, K22 to K28 were ordered in October 1917 but the end of the First World War meant that only K26 was completed.

The double hull design had a reserve buoyancy of 32.5 percent. Although powered on the surface by oil-fired steam turbines, they were also equipped with an 800 bhp diesel generator to charge the batteries and provide limited propulsive power in the event of problems with the boilers.

This pushed the displacement up to 1,980 tons on the surface, 2,566 tons submerged. They were equipped with four 18 inch (460 mm) torpedo tubes at the bow, two on either beam and another pair in a swivel mounting on the superstructure for night use. The swivel pair were later removed because they were prone to damage in rough seas.

They were fitted with a proper deckhouse built over and around the conning tower which gave the crew much better protection than the canvas screens which had been fitted in previous Royal Navy submarines.

The great size of the boats compared to their predecessors led to control and depth keeping problems particularly as efficient telemotor controls had not yet been developed. This was made worse by the estimated maximum diving depth of 200 ft. being much less than their length. Even a 10 degree angle on the 339 ft. long hull would cause a 59 ft difference in depth of the bow and stern, and 30 degrees would produce 170 ft which meant that while the stern would almost be on the surface, the bow would almost be at its maximum safe depth. The problems were made even more dangerous because the eight internal bulkheads were designed and tested during development to stand a pressure equivalent to only 70 ft.

The submarine HMS K5 Sank off Isles of Scilly (unknown cause) 20 January 1921

On 20th January 1921 HMS K5 sailed from Torbay as part of a fleet bound for Spain, which included the Cruiser Inconstant and Submarines K8, K9, K15 and K22. It was decided to conduct a mock battle in the Bay of Biscay and the vessels split up to take their positions. A signal was received from K5 that she was diving, but she failed to reappear at the end of the exercise. An hour before dusk a battery cover from a K boat was recovered and the next morning a sailor’s ditty box was found – the last trace of K5. It is believed an accident caused K5 to exceed her maximum diving depth.

K5 left Torbay on 19 January 1921 with the K8, K10, K15 and K22 for a mock battle in the Bay of Biscay.

The submarine was commanded by an experienced officer, Lieutenant Commander John A Gaimes, DSO, RN, but had a new crew. The other officers on board were Lieutenant F Cuddeford, Engineer-Lieutenant E Bowles, Acting Engineer-Lieutenant G Baker, Lieutenant B Clarke and Acting Lieutenant R Middlemist. The full complement included 51 other ranks on board.

All 57 hands were lost on 20 January about 120 mi (190 km) south-west of the Isles of Scilly. She had signalled that she was diving but she did not surface at the end of the exercise. After a battery cover and a sailor’s “ditty box” were recovered, it was presumed that she had somehow gone past her maximum depth.

On return from her exercises in the Mediterranean in 1922, Hood and the rest of the fleet dropped wreaths and held a memorial service where K5 had gone down.

Problems with the K-class

Retired Rear-Admiral S.S. Hall wrote in The Times (24 January 1921, p. 10): “…it may be taken as certain that the loss of the vessel was due to some delay to checking the downward momentum gained by the vessel being overtrimmed in diving, either by admitting compressed air too slowly to too many tanks at one time, to tanks only partially full, or to a sea connection being closed prematurely.”

The waters where the battle exercises were taking place were so deep that the vessel would have been crushed, losing control due to the intake of water. Admiral Hall wrote that it was “not clear why the ‘K’ class should be taken for cruises in the Atlantic in winter.” He describes the submarines as ‘freaks’ that were designed especially for the conditions of the North Sea during World War I. “The high surface speed necessitates great length, and the further complication of steam demands very large openings for funnels and air intakes to boiler rooms. These have always been a source of great anxiety in bad weather or in rapid diving.”

K13 suffered a similar fate during her acceptance trials, when she foundered with the loss of 32 of those on board. The cause of the incident was related to the openings Hall refers to.

In the end, the boats were pulled from service and replaced by boats that were very different in configuration and propulsion.

Another blogger infamously said that the K Class were an unhappy ship.

The K class of submarines was the brainchild of Admiral Jellicoe. At 339 ft. long they were nearly twice the size of most other submarines. They were made this long to achieve a top speed on the surface of 24 knots. Unfortunately this meant that when the submarine dived, the bow could be at crush depth whilst the stern was still near the surface. The submarines were steam driven with two funnels that had to be retracted before the dive could take place, and this was a constant source of leaks and problems, and was of particular concern in the case of a crash dive or bad weather.

The best submariners are still reliant on the technology of the designers and builders.

I can only imagine their last moments. But I wish their souls to be at rest. They are part of the submarine story.