FAST MINELAYERS
During the First World War, several cruisers were converted as fast minelayers, and proved useful enough for Controller to request a specially-built ship in July 1918.1 The first requirement was high enough speed to slip into nominally German-controlled waters overnight, i.e. 30-35kts seagoing. DNC suggested basing the ship on either Cavendish (the Hawkins class cruiser being completed as the carrier Vindictive) or the new ‘E’ class, preferably Cavendish with a slight bulge (he wanted to try for 32kts). Economical speed would be no less than 20kts, which was appreciably higher than the speed typically aimed at. Radius of action should be at least 2,000nm at 20kts, and 1,000nm at full speed. To get into enemy-controlled waters, the ship had to have a relatively shallow draft, not more than 12–13ft (DDOD(M) considered draft the least important item, however, and DNC decided to adopt the same draft as in Cavendish’). The ship should carry at least 400 moored mines, preferably all internally, on one mining deck (existing minelayers used canvas screens to conceal the mines they carried on their upper decks). The mining deck, the ship’s main deck, had to be at least 430ft long to accommodate this many mines. The need to conceal the minelaying mission also shows in a requirement that the ship resemble a modern warship as much as possible. Devoting the whole main deck to mines would force officers onto the upper deck and ratings onto the lower deck.
How high the mining deck could be (the mine drop should not exceed 12ft) depended on the nature of the stern wave at speed; therefore, a cruiser stern was desirable. Mines would be stowed on four sets of rails, as straight as the curve of the ship would allow, with four traps (for launching) and without any interconnections (points). The ship would have four embarking hatches on each side, each with its own stump mast and derrick, for quick loading. Hatches should lead directly onto the rails, so that mines and their sinkers could be loaded directly onto the ship. Mines would be moved aft to launch by an endless chain or conveyor belt, i.e. should not need bogies (this idea was inspired by US systems then operational for the Northern Mine Barrage). Armament would be six 4.7in or eight 4in guns (the latter option was chosen) and two 3in anti-aircraft guns.
A sketch design showed almost no protection, because mines accounted for so much tonnage. The big Cavendish devoted 616 tons to armament, while each mine weighed 1,850lbs, so 400 of them accounted for 330 tons. Allowing another 1¾ tons per mine for rails, etc brought that to 500 tons, and winches and other mine-related equipment might add 150 tons more, a total of 650 tons before allowing for the gun armament (140 tons). If the minelayer were based on Cavendish, it would be about the same size (11,375 tons deep compared to 11,630 tons). The endurance requirement was difficult because at maximum speed the ship would be burning twice as much fuel per nautical mile as at 20kts.
Alternatively, the minelayer could be based on the smaller and faster ‘E’ class cruiser, with its lighter machinery (this version had 80,000shp machinery rather than the 40,000shp of the Cavendish-based design). In an ‘E’ class cruiser, armament plus protection amounted to 1,055 tons; in addition to minimal protection (90 tons in the earlier design), the ship needed only 790 tons for mines and gun armament. Apparently this too was unsatisfactory, because within a few days Controller decided to abandon the large ship and go instead for a Design G based on the ‘D’ class cruiser: 420ft x 42ft x 15ft deep, 4,100 tons, making 30kts deep or 31kts light with mines on 52,000shp. To get down to this size, the mine load had to be halved to 200 (250 if possible) and armament cut to four 4in or 4.7in guns and one 3in HA gun. Mines would be carried on the upper deck. Radius of action would be as before, using 950 tons of oil (compared to 300 tons in a ‘D’ class cruiser). As before, the ship would be unprotected. A Legend dated 22 August 1918 showed a normal displacement of 4,100 tons, and a deep displacement of 4,850 tons, but there may have been some question as to whether the hull could carry the engines, and a revised statement showed 4,772 tons normal. A key issue in the design was whether E-in-C could provide 13,000shp in each of four boilers. Cost would be £480,000 and building time twenty-two months.
The project lapsed about in August 1918, perhaps because the end of the war was coming into sight, and was certainly less than twenty-two months away. However, the idea of the cruiser minelayer survived, to be revived in July 1920. Controller revived the 1918 requirements (at least 250 mines, to be carried internally on one mining deck) but specified sea speed and radius corresponding to those of a light cruiser of the same date and construction. The specified battery was a good antiaircraft armament. Controller expected a displacement of 4,000 to 7,000 tons. DNC told his cruiser designer, Lillicrap, to base the ship on an improved ‘D’ class cruiser with bulges, to achieve 28kts in deep condition, and 29kts with half-oil; anything more would require a much larger ship (the PWQ Committee wanted 30kts deep, and 6,000nm at 14kts).2 A first cut showed a displacement of 4,900 tons, but that soon grew to 5,400 tons, including 300 tons of oil fuel (1,300 tons fully loaded) and eight 3in anti-aircraft guns. Further analysis showed grossly insufficient stability, so beam had to be increased considerably.3 As before, the weight of mines and associated equipment (375 tons) dwarfed that of the gun armament (70 tons). The ship was unprotected apart from bulges. She would have had 1,600 tons of oil to achieve the desired (cruiser) radius of 6,000nm. The 1,000nm and 2,000nm figures chosen in 1918 had been associated with a North Sea rather than a Far Eastern war. DNC ordered the use of ‘D’ class machinery.
In October, after attending a minelayer conference, DNC asked whether mines could be stowed on two decks and also whether it might be better to convert an existing cruiser. A Chatham could be converted to oil fuel, its upper deck covered over and used for mines. As much armament as possible would be retained. Candidates were Southampton, Lowestoft and Birmingham, all of which were currently serving on foreign stations (South America and Africa). Four guns would be removed, leaving three forward and one aft on the forecastle deck. The submerged torpedo room would be eliminated and converted to oil stowage, giving a total of 1,300 tons (for 5,000nm). About 200 mines could be stowed on the upper deck, fed by rails to two traps. The forecastle deck would be extended aft to cover this mine deck and the ships’ sides built up. Conversion would cost about £231,000, compared to over £900,000 for a new ship. CNS turned down the idea late in October 1920, and attention turned back to the new minelayer.
The Staff considered that the 6,800-ton ship met the stated requirements, but the Staff asked for more mines. DNC offered to stow them on the lower deck, but that was considered objectionable.4 It proved possible to rearrange the mine deck to stow twenty more mines (300 in all). Increasing the mine load reduced oil fuel capacity, but it was clear that machinery space was available (Royal Navy practice was to stow oil fuel below the platform deck, so added machinery volume could not be freed for oil). On 7 February 1921 DNC proposed adding a diesel, both to gain cruising radius and also to gain experience with cruising diesels. At a Controller’s conference E-in-C agreed with the idea, and Controller concurred. The diesel would nearly double endurance to about 13,000nm at 13kts, one steam boiler being kept lit for auxiliaries. With the diesel, the ship would displace something over 7,000 tons, compared to the earlier 6,800 tons.
Both 6in and 4in guns were suggested as alternatives to the 3in HA battery, the choice falling on six 4in HA. A conference on 8 March 1921 decided that armament would be four 4.7in HA guns (otherwise installed on board the Nelson class battleships and the aircraft carriers Courageous and Glorious, with 200 rounds per gun) and two of the multiple pompoms just specified by the Naval Anti-Aircraft Committee. Armament weight increased from 110 to 140 tons. The design grew further.5
The new minelayer was HMS Adventure, the first post-First World War cruiser, albeit a special-purpose ship. As completed she had the first British transom stern. On trials, the transom created unusual water conditions, the wake suddenly spurting out above 24kts, and also created a suction effect which drew mines towards the stern after they were released, and the ship had to be rebuilt in 1931–2 with a more conventional rounded stern (which added 19ft to her length). This experience was reviewed when a transom stern was chosen (as a way of reducing resistance) for the Fiji class cruisers.
A second cruiser minelayer was included in the proposed 1924/5 programme, but it was not ordered.6 At his conference on 12 November 1923 Controller decided not to fit a diesel; the ship would presumably have been a repeat Adventure in other respects (Controller specified the same 40,000shp powerplant). That made sense, as Adventure was experimental and would not be completed until 1926. At the next meeting (on 26 November) DNC said that as there were considerable alterations to Adventure required on account of different machinery arrangements and other requirements from various departments, the ship could not be ready ‘at the early date given’. In December, DNC said that no progress on the new minelayer could be made until work on the new cruisers (the Kent class) had eased off; he thought he could have a design in February 1924. E-in-C and DEE could both be ready in mid-February. DNC renewed this pledge in January 1924. No design emerged, because the second minelayer soon disappeared from the approved building programme.
Adventure as fitted on completion, January 1927. Dashed lines show how the stern was lengthened in 1932, overall length increasing from 520ft to 539ft. The inset shows the original diesel exhaust stack, replaced by the end of 1926. The diesels were removed altogether about 1938. The weather deck abaft the vertical spray shield at the bow was probably planked but is not shown as such in the drawing. The 1927 ‘as-fitted’ plan shows a folding spray shield extension, but it appears either not to have been fitted or not to have been retained. Note that the forward mine-loading hatches served the outer mine rails and the after hatches the inner pair. By 1942 the single pompoms had been replaced by one octuple pompom in ‘B’ position, and the 4.7in director on the upper foremast platform had been replaced by a standard HA director carrying Type 285 radar. The foremast had been cut down, the mainmast restructured as a tall tripod, and nine single Oerlikons added. Design speed on steam power was 28kts, and by the middle of the Second World War her best speed was 27kts. At about the same time Vickers designed a cruiser-minelayer for Spain (Design 1040, 7 July 1923), to carry the same mine load (400) as Adventure. She had the usual Vickers cruiser battery of two twin and two single 6in guns, two 4in HA and two sets of 21in torpedo tubes. She would have displaced 5,750 tons normal (430ft pp, 458ft loa x 54ft 6in x 34ft x 16ft), making 25kts on 23,000shp (radius 5,000nm at 15kts). This design was probably related to an earlier unnumbered design, dated 1 9 June 1 923, for a 4,150-ton (400ft x 50ft 5in x 24ft x 13ft) cruiser armed with three 6in/50, two 105mm HA and 400 mines; power would have been 20,000shp for 25kts (there was also a 15kt, 2,750-ton version armed with two 6in/50). No such ship was built (the Spanish Navy did later build some minelaying gunboats). The only inter-war equivalent to HMS Adventure was the French Pluton. In addition to the design for Spain, Vickers offered Turkey a small ‘torpedo cruiser’ (actually a minelayer, the title probably referring to the fact that mines were originally called torpedoes), Design 930 of 25 August 1927. She would have displaced 2,500 tons on trial (380ft x 37ft 9in x 23ft x 10ft 10in) and would have made 36kts on 52,000shp (five oil-fired boilers). Armament would have been sixty mines plus three 6in guns, two 3in HA, four single pompoms and two triple 21in torpedo tubes. Like the Spanish ship, this one did not materialise. When the Turkish Navy ordered four destroyers from Italian builders in 1930, two of them were equipped to lay mines. (A D Baker III)
HMS Adventure as completed, showing the transom stern which caused such problems. She was given an unusually powerful anti-aircraft battery because aircraft would her main enemies during mining sorties. By 1937 the AA rearmament programme called for her to receive one octuple pompom and two 0.5in machine guns, plus one set of HACS III*C. However, that was not done for some time.
Adventure is shown on 10 April 1942 after refit. Note the round stern introduced to solve the problems created by the transom. The single antenna on the mainmast is for the rotating version of the Type 286 radar, just fitted. An earlier 1942 photograph shows the Type 285 atop her HA director (as here) but a DF coil atop her pole mainmast.
The main improvement to HMS Adventure before 1939 was the addition of a pair of quadruple 0.5in machine guns by April 1939. By October 1941 she had been fitted with an octuple pompom in ‘B’ position; installation was presumably delayed because of a shortage of such mountings, and because it was assumed that the ship would operate mainly at night (she did have a high priority for installation of an early air-warning radar). By October 1942 her quadruple 0.5in machine guns had been landed, and she had seven Oerlikons. By April 1944 she had been upgraded to four twin power and ten single Oerlikons. In 1943 proposals were made to rearm her.7 The initial proposal was to remove the 4.7in guns and lighter weapons (but not the pompom), and to mount four twin RPC 4in in their place. Two quadruple 0.5in guns might have been retained. Another possibility was three twin upper-deck 4.5in mounts. Neither refit was carried out. She was reportedly converted into an emergency repair ship for landing craft to support the D-Day operation, but the official list of British and Commonwealth warships continued to describe her as a large minelayer even in October 1945, when she was laid up disarmed.
By 1936 there was interest in a replacement for HMS Adventure. In October 1936 DNC laid out requirements: high speed (38kts), a heavy gun battery (six 5.25in, two quadruple pompoms and two quadruple 0.5in machine guns, but no torpedoes). The ship should carry 360 mines.8 This time cruiser protection was wanted (approximately 3in side and 2in deck for magazines ([later 4in side and 2in deck were chosen], but apparently little or nothing over the machinery).9 DNC estimated the ship would be 620ft x 63ft and would displace 9,000 tons. Design estimates began with a detailed calculation of the required length of the mining deck. A rough Legend suggested that the ship could be built on 8,945 tons at a cost of about £2,110,000.10
The single fast minelayer was dropped in favour of building four smaller ones, each to carry 100 mines.11 A draft Staff Requirement was circulated in February 1937, by which time some preliminary work had presumably already been done. The ships would rely on their speed to evade surface attack; the Staff wanted 40kts in standard condition (hence 37-38kts in deep condition). Endurance should be appreciably greater than (later amended to ‘not less than’) that of the ‘Tribal’ class, as the ships might have to carry out strategic mining operations subsidiary to main fleet operations (as was done by HMS Abdiel after Jutland). The target was 6,000nm at 15kts when six months out of dock. The Staff envisaged a ship of about 2,000 tons, as seaworthy as a modern destroyer. Mines would be laid at 20kts, with 120ft spacing. Armament would be primarily HA, allowing four guns to engage a single aircraft, i.e. four 4in HA. One quadruple pompom, with a wide arc of training on each side, was also wanted. Stabilisation was written in as a requirement. Later the Staff Requirement was amended: the ship should be able to carry fifty more mines at a cost in speed.
This project, which became the Abdiel class, began as design K33, in the same series as the Fijis (K32 was probably the larger minelayer). Her hull form was initially based on that of the slightly smaller ‘Tribal’ class destroyer; at about 2,600 tons she was expected to be 400ft (wl) x 39ft x 11ft (depth 24ft amidships), carrying 100 mines on a 234ft mining deck. Work on the preliminary design was well advanced by late June 1937, E-in-C providing machinery space dimensions.
DNC submitted a sketch design in April 1938 for a 2,600-tonner. Although the ship was not much larger than a destroyer, she had considerably more powerful machinery, two-shaft turbines fed by four boilers. There was no space for the sort of alternating engine and boiler rooms characteristic of cruiser designs. Instead, the boilers were in two adjacent rooms, the uptake from the after boiler of the forward boiler room and that of the forward boiler in the after boiler room being trunked together to form the middle of three funnels. In the initial design power was 70,000shp – a cruiser powerplant. The ship was rated at 39.75kts in standard condition and 37kts deeply loaded. Endurance was 5,500nm at 15kts. The ship had two mine rails extending forward to the fore end of the forward boiler room, with endless chains to move the mines to the stern. The mine rails ran in passages alongside the machinery spaces. The fire-control system for the two twin 4in guns was that of the rearmed ‘W’ class destroyers (‘Wairs’), with a transmitting station below decks. It housed a Fire Control Box, which contained both HA and LA computers.
HMS Welshman is shown as completed in 1941, with a fixed-antenna Type 286 radar on her foretop.
Controller (Rear Admiral Henderson) was unhappy with the armament of only two twin 4in; he wanted a third added on the after superstructure (which he understood would cost 60 tons and a quarter-knot). Alternatively, the 4in guns could be replaced by powered weather-proof twin 4.7in guns (as in ‘L’ class destroyers), probably at the cost of an increase to 2,720 tons (and the loss of about half a knot). A third possibility was to add two quadruple torpedo tubes (2,680 tons). Henderson thought HA fire was overrated; as many others in the Royal Navy pointed out, although the 50° ‘L’ class mounting could not elevate as far as a 4in HA gun, it could deal with an aircraft flying at 6,000ft or below up to the moment of bomb release, and it lost aim on an aircraft at 16,000ft for only 13½ seconds before the moment of bomb release. A very fast minelayer would be a poor air target in any case. It might have a much greater need for good LA armament, and it might find lucrative torpedo targets during minelaying runs. But ACNS pointed out that Controller had misunderstood the meaning of ‘offensive’ in the role of the ship. The minefields were offensive, but the ship was expected to avoid action, hence her high speed. ACNS liked Controller’s suggested six 4in battery, which could engage dive bombers, and which did not require power operation, and having four guns bear aft would be particularly useful for a ship trying to escape enemies. The 4.7in guns cost too much speed and could not engage dive bombers. Despite the relative failure of the 4in HA gun, on balance the three-mount battery was the better choice. It was also better than fitting torpedo tubes. If the ship were surprised while laying mines, she would turn and run, in which case good torpedo firing solutions probably could not be developed. First Sea Lord was inclined to go for six 4in and one set of torpedo tubes.
As to whether the extra twin 4in gun should be forward or aft, ACNS observed that placing it forward and the pompom aft would give the latter the widest possible arcs, placing the two guns forward being slightly better (if spray could be avoided). In that case perhaps the after superstructure could be eliminated, the pompom and its director being placed on bandstands. That was impossible. As with HMS Adventure, the mining deck took up considerable internal volume, some of which was gained back in the superstructure. The after 4in gun had to be moved aft to provide more space for the Captain.
DNC considered carrying the fifty extra mines on the upper deck, but that gave too great a drop (about 20ft). It turned out that the two main mine rails could be curved to allow four lines of mines abaft the machinery on the mining deck. The outer rails could be extended forward into the accommodation spaces. Total capacity was increased to 120 mines. DNC offered two twin 4in aft and one forward; if he placed the additional 4in mount forward, he would have to raise the bridge. DNC understood that two four-man directors were required, so with one of them aft, placing the extra 4in gun there required that the pompom be relocated; he proposed placing it between the centre and after funnels. DNC pointed out that fifty more mines would add weight, and that they could be carried only if a reduction to 39.5kts could be accepted.
In July the forward position of the extra 4in mount was approved. DNO pointed out that in that case the after director was not needed, freeing a position for the pompom much better than the one between the funnels. There was sufficient space for an octuple pompom in the same position, but this possibility was never realised. The bridge was raised to clear ‘B’ 4in mount. It was essentially the angle-sided bridge adopted in the ‘Tribal’ class and later destroyers, but with a large gun crew shelter for the crew of ‘B’ mount built out from it. These features figured in the final design reflected in a Legend dated November 1938. Now the ship displaced 2,650 tons rather than 2,600 tons in standard condition. To maintain the 39.75kt speed in that condition, power was increased to 72,000shp; speed at deep displacement was 36kts.
The Board approved the Legend and drawings of the three 1938 ships, Abdiel, Latona and Manxman, on 1 December 1938. A fourth ship, Welshman, was included in the 1939 programme, and two more (Apollo and Ariadne) were included in the 1941 programme. In these two ships B’ twin 4in mounting was replaced by a second multiple anti-aircraft weapon, both of which were Hazemeyer twin Bofors instead of pompoms.12 A proposal to include additional ships in the 1943 programme was rejected.13
Above and below: Abdiel, lead ship of the new fast minelayers, is shown on 8 May 1943. The big cranes visible in the view from astern were used to load mines through hatches onto the mine deck below the upper deck. The combination of space and high speed made these ships ideal for running high-value cargoes into besieged places like Malta. Conversely, their limited endurance made them ineffective for Pacific warfare as it was developing in 1944–5.
Latona is shown as completed. The accommodation ladder is shown in both deployed and stowed positions; the ‘Mediterranean’ ladder is shown deployed. It was stowed athwartships just abaft the after funnel. Early design sketches showed tilted rather than upright funnels, and ‘B’ gun in the superfiring position aft. Contrary to some publications, these ships were never armed with 4.7in guns (nor was there any interest in such armament; the main threat they faced was from the air). Latona had a very short life: completed on 4 May 1941, she was lost to Italian bombs off the Libyan coast on 25 October. (A D Baker III)
As war approached, on31 August 1939 DNC asked for a more austere minelayer, to carry 150 mines with the original armament of two twin 4in and one quadruple pompom, but with speed cut to 30kts.14 His designer pointed out that, as in the other designs, the sheer size of the mine decks dominated any cruiser minelayer design. Experience with destroyers suggested that the powerplant needed (about 30,000shp) could be squeezed under the main deck, freeing enough space for four lines of mines. Abdiel required a total rail length of 380ft from the after bulkhead; in this ship only 190ft might be needed. Lillicrap thought that the ship might displace about 1,800 tons (350ft x 56ft x 10ft), with a 26,000shp powerplant. Endurance would match that of the fast minelayer, 5,500nm at 15kts. Cost would roughly match that of the fast minelayer. If the 30kts referred to deep condition, the ship would make 32.5kts in standard condition, and she would need 32,000shp (1,950 tons). Alternatively, 30kts in standard condition might equate to 28.25kts in deep condition. Nothing came of this estimate.
The mine deck of HMS Latona shows just how much space even 100 mines occupied, and, by extension, why these ships were effective carriers of high-value cargo to Malta and to Tobruk. For much the same reason the US Navy adapted its large-minelayer design (Terror) to carry first nets and then amphibious vehicles. (A D Baker III)
Above and below: Apollo was lead ship of the repeat Abdiel class. She is shown on 26 February 1944. Note the elimination of ‘B’ twin 4in gun in favour of a twin power Oerlikon. She also has the self-contained Hazemeyer twin Bofors guns with their on-mount Type 282 radars.
Above and below: Apollo was recommissioned in 1951 for the Korean War emergency, remaining in service aftewards for a decade. She is shown on 21 October 1954, stripped of her light weapons and provided instead with the new twin 40mm Mk 5 guns. She had laid minefields in support of the Normandy invasion (to protect the invasion force from German light forces and U-boats); she also laid ASW minefields in 1945. Manxman was also recommissioned (for the Mediterranean), but went back into reserve in 1953. She was recommissioned in 1956 as flagship of Mediterranean Fleet flotillas, and served at Suez before going back into reserve. For this service her after 4in gun was landed and a large deckhouse fitted. The third surviving ship, Ariadne, was refitted for recommissioning at the time of the Korean War, but that was not done. Similarly, she was brought out for Suez, but she could not be manned, and so was put back into reserve. She had the distinction of serving with the US Seventh Fleet (deployed May 1944), laying a field of 146 mines off Wewak, and then was nominated for use as an assault troop carrier. She was converted for this role and landed troops (presumably she served as a very fast APD) at Leyte Gulf. She was then converted back, returning to the United Kingdom in time to lay a number of ASW fields with HMS Apollo.
