KXI class submarine (1924)

K XI, XII, XIII: Patrol submarines (1924-1945)

The K.XI (or K 11) class were three submarines built by Fijenoord shipyard in Rotterdam for the Royal Netherlands Navy that draw lessons from the previous K VIII class and improved on many points. They were the last ordered in WWI, by 1918, to be still active in WW2. This time their design derived enough for from the original Holland type to be called purely a Dutch design. Some influenced were still there, but they improved the envolope in all areas: Larger, with a stronger hull to dive at 200 ft or 60m, more torpedoes, and a better range. They joined the KNIL after completion in 1925 and patrolled the Dutch colonial waters during the interwar. When World War II broke out, K XII ended scuttled in 1942 while under repair at Soerabaja to prevent capture but K XI and K XIII soldiered on from Australia against the IJN until 1945…

Hr.Ms. Mark K. XII on trials st Den helder in 1925

Development of the K XI class

The previous K VIII were themselves derived from the K.V and themselves evolved from the prewar K.II, built at Fijenoord rather than De Schelde and like all of her generaiton, she was not delivered before the end of the war due to shortages notably of equipments from some belligerents. The K VIII was still a medium-sized diesel-electric patrol submarine optimised and “tropicalized” for extended colonial service in the East Indies with the KNIL with a top speed of 15 knots and limited range of 3,500 at 11 knots whereas the K VIII of the 1916 program were assigned De Schelde fior a coinstruction start in 1917. They were a bit larger and with significant differences.
Recall here: The ‘O-names’ were destined to home waters in the Netherlands, and generally smaller, better suited for North European waters. “K” boats referred not exactly to the KNIL but for the “colonies” (Koloniën). They were generally larger, with better range, and tropicalized, ie. having internal air climatizer, which was rare at the time, and only adopted by the US in WW2 for Pacific service for example.

K XIII in Ambon Harbour 1942

The K.VIII planned in 1914 had their design completed by 1916, with some experience return. They retained all the hallmarks of the classic Holland design, however the Dutch Admiralty wanted to improve range for the Pacific and under the licence, they were based on the 105 H design. The three boats were ordered together on 27 June 1917 at Koninklijke Maatschappij De Schelde but not launched before 1922, five years and the last in mid-1923, last completed by December 1923. A lot of wartime experience was gained in between by studying notably U-Boat operations, and entente submarine logs through their naval attachés in France and Britain. So a lof of thought went into the new design planned in 1917, but only authorized in 1918. They were designed under the lead of Dutch engineer J.J. van der Struyff.

The new K XI were definitively to be a much larger design for the Pacific, as shown by the successes of the U-139 U-142 class “U-Kreuzer” off the US coast. It might be useful to have a submarine with the reach to the southernmost Japanese islands or attack their approaching fleet at a safe distance from the East Indies. For this, there was no way around it, the KNIL needed a larger hull to accomodate extra fuel for this extra “legs”. Speed was less a priority, either surfaced or submerged, and this depended heavily on the types of diesels used anyway, with the belligerents still at war when they were studied, so no model could be delivered with ease. This uncertainty aside, it was believed that diving deeper was a recipe for survival, and “laying low” in ambush close to an enemy harbour was a valid tactic. And to go with this extra range, it seems natural to have enough space for more torpedoes. There would be mix of external and hull tubes, of two calibers, one usable against commerce.

All three were eventually ordered from Fijenoord shipyard in Rotterdam. Despite being ordered in 1918 they were only laid down from 1922-23 and launched 1924, completed in 1925-26. The gap between 1918 and 1922 allowed not only to make many modifications in the design, but procure all the material from former belligerents, now at peace. Despite a construction of four yearswas still extensive for submarines, but this reflected of a care given to construction and completion.

Design of the K.XI class

The K V XI were essentially longer submarines compared to the previous classes as seen above, and like their predecessors they were supposed to run on MAN diesels so the latter after 1922 were supposed easier to acquire. They had more powerful models, whuch enabled a greater top speed surfaced, 17 knots contracted. To compare their predecessors of the K VI, the ones unlucky enough to be barred from the MAN diesels because of the war ended with Swiss Sulzer diesels instead and only capable of 15 knots. But when the K VI saw their traversing surfaced tubes an issue in case of depth charge attacks, never installed, and so was the case for K XI class. Instead they mixed calibers. For the hull they retained the same Double-hull type, but with 6 ballast tanks, and a pressure hull made of even thicker steel so to dive deeper. The larger conning tower allowed the use of two periscopes with a larger stroke than their predecessors, for 4 meters, enabling greater submersion at periscope depth, making aircraft detection more difficult. Their predecessors ditched the old 7.5 cm for a “dual purpose” 8.8 cm and so this was repeated on their design. The K XI was supposed to prey on commerce, so four tubes were mounted in the bow, tw 530 and two 450 mm, with a single defensive one at the stern, like German U-Boats. The 8.8 cm gun was a good match to prey on trading vessels, but the mount enabled great elevation so they were as much defensive as the light AA they carried.

Hull and general design

The K XI was not anymore based on drawings from ELCO, but those of J.J. van der Struyff at De Schelde to produce master drawings. They recycled many ideas of the ones drafted at Fijenoord as well. The K XI class were much larger submarines than the previous ones, in fact they were the largest Dutch submarines built so far, at 688 tons surfaced and 828 tons submerged versus 520 long tons standard, 583 long tons (592 t) full load for the K VIII. They were also marginally longer at 66.7 m (218 ft 10 in) but much beamier at 6.15 m (20 ft 2 in) and with a greater draught at 3.78 m (12 ft 5 in) (versus 64.41 m (211 ft 4 in) overall, 5.6 m (18 ft 4 in), 3.55 m (11 ft 8 in)) on light load. To be more precised they had a fully loaded, submerged displacement of 828 tonnes. So 612 tonnes light, as built, 688 tonnes surfaced, standard and 828 tonnes underwater and fully loaded.

The hull was a bit different in general outlook, with the forward hull having two recesses anchors forward, same freeboard for surface seaworthiness, blister ballast with gradual curve. However there were significant differences as well:
-The bow, like the O class, was now curved on its upper edge, no longer straight.
-The other striking difference was their forward raised deck, some 50 cm (1.5 ft) above the normal deck to improve seaworthiness.
-They now have a full double hull, no longer a pressure hull with blisters for ballasts: Along with the O 9-class boats, this was a first for Dutch submarines.
-The now could dive at 60 meters (200 ft) thanks to the thicker hull, still less their own lenght with a crushing depth likely around 100m.

They kept the classic Holland extended conning tower, still with an open helmsman post as well as a rear observation platform and free aft deck for AA. The hull was made larger to accomodate two periscopes, one for attack and one for watch, both 4 meters tall. They also had two “snorkel masts”* behind, and the wireless radio cables anchored on a telescopic portico amidship, then braced on two poles fore and aft.
The transition between the blisters and main upper hull were quite smooth indeed to streamline the hull and increased underwtater speed, but still with relatively few water scoops above the ballast line for the outer hull, so diving time was not stellar. The ballasts were three groups, all with kingston systems pneumatically operated, remotelly from the control room below the CT.

The pressure hull was now an internal, separate tube, not only keeping needle-like ends for the torpedo sections fore and aft, but also thicker (the Dutch made armour at the time and they planned 280 mm plating for some of their new planned coastal battleships, on these subs it was likely around ). The tail was narrowing up to a fin in pure Holland fashion, with a cross tail aft still typical Holland style with side guards acting as tails and stabilizer planes, wrapping the two propellers. This was the only clear leftover of the previous design. They carried 31 men total including 5 Officers but in wartime their crew grew larger.

Powerplant

When the previous K VIII obtained two 900 hp (671 kW) 8-cylinder MAN 2-stroke diesel engines, the new design was 120 tonnes heavier and better engines were needed not only to compensate, but for better speed altogether. So it was planned 1200 hp MAN diesels. Now that they could be delivered by Germany at peace, this avoided the pitfall of adopting Sulzer 600 hp diesels for a lame 15 knots surfaced on their precessors. Thus, the K IX obtained two brand new 1,200 hp M.A.N. (895 kW) reversible four-stroke diesel engines without hassle. This extra output made for a total of 2400 bhp surfaced (1800 kW) for a top speed from 16 knots to 17 kn (31 km/h; 20 mph) surfaced, comparable to the best standard surface speed at the time. The objective of 18 knots was only reached practically in WW2.
When submerged, they depended on 132 battery cells total, capable of delivering 4,500 Ah over a three-hour period. They fed to electric engines rated for 8 knots (15 km/h; 9.2 mph) submerged.
They carried 45 tonnes of fuel oil (46,7 m3) for a surface range of 3,500 nmi (6,500 km; 4,000 mi) at 8 kn (15 km/h; 9.2 mph) and they ran at 25 nmi (46 km; 29 mi) at 8 knots (15 km/h; 9.2 mph) submerged.

Armament

Instead of the six tubes of the K.II, K V and K VIII, all uniformely 450 mm (17.7 in) (four in the bow*, two in the stern). *surface traversing tubes were changed for fixed bow tubes for the K VIII. However wartime exprience showed the now “normal” caliber for submarines should be the same for surface vessels, 530 mm (533 mm or 21 inches on the angloshpere). Four 53 cm were too large for the hull as it was and torpedo storage still unsufficient so a compromise was made, with two 53 cm tubes above, two 45 cm tubes below in the bow and two 45 cm in the stern. The 53 cm were reserrved for military targets, warships with ASW protection, and 45 cm for all the others, mostly merchant vessels.

This made for a total of six fore and aft pressure hull tubes but instead of ten Type III torpedoes in storage, they now had twelve Type III (45 cm) and Type I (53 cm). Like two for the 53 cm tubes, two spares and the remainder for the 45 cm tubes so four spare, likely forward. The deck gun was the same 88 mm (3.5 in) as before, probably with extra ammunition storage. AA machine gun aft of the CT were included from the start. In 1918 nobody scoffed at aviation anymore. This was a marine, liquid-cooled 12.7 mm/90 or 0.5 in. M1920 Colt-Browning Navy type but from the late 1920s. The USN also made it standard over the air-cooled Browning due to obvious seawater spray rust concerns. If there was another 12.7 mm AA mounted at completion, the type is unknown.

Type 53I Torpedoes

The novelty of the design. They were made at the Whitehead manufacture of Saint Tropez on the French Riviera from 1923 and were adopted for the first time for the K XI class.
The first of these 21″ torpedoes arrived in the Netherlands in 1923. This torpedo was used on the K XI class and the O 9 class. The Dutch Navy bought a total of 27 (incl. surface fleet) I 53 torpedoes.
Specs:
Diameter 21″ (530 mm), Weight 1437 Kg, Length 6.84 m.
Power plant: 4 cylinder radial engine, compressed air.
Warhead 250 Kg TNT. Range/Speed: 4,000 m (13,000 ft) at 39 kts or 10,000 m (33,000 ft) at 26 kts

Type 53II Torpedoes (1930)

Note that before 1930 they likely had been replaced by the Type II, in service from 1928, 200 purchased from the factory in Weymouth.
Specs: 1,525 ton, 300 kgs. TNT warhead, range 4,000 meter at 42 knots or 10.000 meter at 28 knots.
The type II53 became the standard for Dutch Submarines in WW2 and still in service by 1946.

Type 45III Torpedoes

Whatever the launch mode, these were of the British class 18-inches type Mark III (In Dutch service called the “Type III”). The latter model was developed from the Holland type submarines and was mass-produced both in the US and Britain for them. It weighted 845 pounds for 140 inches (3.55 meters) in length, 17.7 inches (45 centimeters) diameter, and an effective firing range of 800 yards.

The Warhead carried 118 Ibs of wet guncotton, activated by a Mk 1 contact exploder. It was powered by a 3-cylinder reciprocating engine to 27 knots with a depth control system and gyroscope to remain on course. In all, these submarines carried 12 of them. The Mark III or in Dutch “Typ III45” was manufactured at the torpedo factories in Weymouth and Saint Tropez and used from 1922 to 1946 with 129 purchased. It weighted 785 kilograms for 5.43 meters and carried 165 kilograms of TNT for a range of 2,000 meters at 40 knots and 6,000 meters at 26 knots
based on its 4-cylinder pneumatic radial engine. This was later likely upgraded to new models in the late interwar.

88 mm deck gun

This gun was a Bofors No. 2 L/45 gun or 8.8 cm (22pdr) Bofors, aka No.2. Unfortunately, no data available. Both the photos and barrel length seems to point out to a Krupp 8.8 cm marine design produced by Bofors under licence. In research. As for the AA, these were Browning 0.5 inches or 12.7 mm fitted likely 1925-28, so almost from the start.

Sensors

Hydrophones seems to be in 1919 German ones from Atlas Werke, C type, to identify enemy convoys 10 miles away. It was perfect to use the rüdel tactics, submerged approach of a convoy (presumably Japanese here) over long distances, to a launching position, most preferable at 90 feet deep. 1

Author’s rendition from the plans

⚙ K.XI specifications
Displacement	688 tons surfaced, 828 tons submerged
Dimensions	66.7 x 6.15 x 3.78 m (218 ft 10 in x 20 ft 2 in x 12 ft 5 in)
Propulsion	2× 1,200 bhp (895 kW) diesel, 2× 327 bhp (244 kW) EM
Speed	17 kn surfaced, 8 kn submerged
Range	3,500 nmi at 8 kn surfaced, 25 nmi at 8 kn submerged
Armament	2× 53, 4x 45cm TTs (4 bow, 2 stern), 88 mm Bofors, 12.7 mm HMG AA
Sensors	See notes, Atlas C type
Max depth	60 m (200 ft)
Crew	31

Career of the K.XI class

K.XI (1924)

K XI was laid down on 9 December 1922 as Yard #294, launched on 24 April 1924 and commissioned on 24 March 1925, pennant N53. On October 15, 1925, the K XI departed for the Dutch East Indies under the command of Lieutenant First Class G.E.V.L. Beckman. She stopped on her way off Tunisia where F.A. Vening Meinesz could measure gravity anomalies. She arrived in Sabang on December 28, 1925. No logs for her interwar carrer. She likely patrolled east indies waters with ports visits and exercises like her sisters, in the same unit, homeported at Sabang and in occasional refits as Surabaya.
When the Netherlands wereuinvaded in 1940 and until war on Japan, K XI operated from Surabaya, concerned by German commerce raiders in the region. In early 1941, K XI was assigned to the 2nd Division of the submarine flotilla. In addition to K XI, K X, K XII, K XIII were in that unit. From December 8, 1941, to January 23, 1942, K XI operated under British operational command. She conducted patrols east of Malaya. From January 23, 1942, until the fall of the Dutch East Indies in March she was undergoing maintenance. She made a single patrol afterwards, west of Sumatra. Following the fall of the Dutch East Indies, K XI fled to Colombo, rescuing underway 18 survivors from HMAS Yarra, British supply ship Anking, Dutch merchant vessel Parigi, all savaged by the Japanese.
In Colombo, K XI took orders from the british command and was sent on April 16, 1942 for a first patrol in the Indian Ocean. She made another, but back to Colombo given her general state and age (with the British providing replacements), it was decided not to risk her at sea anymore. Until February 1945, she was used as a target vessel by the Royal Navy and the Royal Indian Navy for ASW and ASDIC trials.
At the request of the Royal Navy, K XI was transferred to Fremantle on 20 February 1945 and crewed by personnel meeded in Australia. K XI departed Trincomalee for Fremantle on 3 March, arrived on 22 March. In early April 1945, K XI was decommissioned, with her remaining crew transferred to other boats. She was partially dismantled and cannibalized to maintain her sisters, then scuttled at the ‘ship graveyard’ west of Rottnest Island. Her shipwreck was rediscovered on 1 January 2025, a few kilometers from the location where it was officially recorded sunk. Note: No photos of the K.XI.

K.XII (1925)

K XII was laid down on 9 January 1923 as hull 295, launched on 15 July 1924 and commissioned on 19 May 1925 under the pennant N61. On September 19, 1926, she departed Den Helder for the Dutch East Indies, arriving in Surabaya on December 29. K XII was one of the six taking part in the colonial fleet review on September 6, 1938 in Surabaya for the 40th anniversary of Queen Wilhelmina’s reign. From September 1939 to December 1941, she took part in large combined exercises round the Dutch East Indies. After June 1940 she patrolled against possible German commerce raiders.
By late 1941, K XII was assigned to the 2nd Division (see above) and from December 7 to December 16, 1941, she patrolled the South China Sea. She managed to spot and sink two Japanese ships, an unidentified cargo ship of c8,000 tons on December 12, and the Japanese tanker SS Taizan Maru (3,525 tons) on December 13.

From December 9, 1941, to February 1943, K XII fell under British operational command based in Singapore. While returning after a patrol west of the Anambas Islands, K XII rescued nine survivors from a British PBY Catalina seaplane. None of her next three patrols were successful. Once back under Dutch command, she made another unsuccessful patrol southeast of Sumatra. On March 6, 1942, K XII was one of the last to leave Surabaya to Fremantle, Austrlia. She arrived safely on March 20. From Australia, K XII mainly performed the landing and recovery of agents in occupied Dutch East Indies. The Royal Netherlands Navy placed K XII and K IX and both their crews under command of the Royal Australian Navy next for anti-submarine warfare training. From June 1943 to February 1944, K XII served as “big boat”, target vessel for ASDIC training. The Dutch Navy decommissioned her in September 1944 given her age and the RAN intended to purchase her but the US command barred this acquistion, arguing she was too unreliable due to her age.

K.XIII (1926)

K XIII was laid down on 15 October 1923 as hull number 296, launched on 23 December 1924 and commissioned on 29 March 1926 (no pennant). On May 27, 1926, K XIII departed from Den Helder for the Dutch East Indies, arriving in Surabaya on December 13, 1926. Underway she hosted F.A. Vening Meinesz to take gravity anomalies on the long route via the Panama Canal instead of the Mediterranean like her sister K XI. She stopped underwy at Horta, Las Palmas, Willemstad, Colón, Mazatlán, San Francisco, Honolulu, Guam, Yap, Manila, Ambon, and Burma.
In 1929 and 1930, K XIII carried Prof. Vening Meinesz and his team for three other scientific trips in Asia. She took part also in the naval review in Surabaya on September 6, 1938.

In early 1941, K XIII was assigned to the 2nd Division under command of Henry Coumou, Lieutenant Commander (1st Class), Reserve. From December 9 to December 27, she operated under British operational command. She made a patrol in the South China Sea, trying to attack the underway Japanese invasion fleet she spotted, but she launched and missed. On December 21, while K XIII was in Singapore, an explosion of her batteries caused 3 men killed, 3 injured and major damage. After the fire was extinguished, decision was made the same day to sail back to Surabaya for repairs, escorted by the destroyer HNLMS Van Nes. They arrived at Surabaya on January 6. When the city was about to fall to the japanese, repairs were still ongoing so she was moved into the port, close to the entrance and scuttled on March 2, 1942.
She remained there until raised and scrapped postwar as a navigation hazard.