5

The Frigate Programme

THE END OF THE Second World War found the Royal Navy in possession of a massive fleet of escorts, ranging from the early-war ‘Flower’ class corvettes and ‘River’ class frigates, to the later and more capable vessels of the ‘Castle’, ‘Loch’ and ‘Bay’ classes. Also in limited production throughout hostilities were the Black Swan class sloops, which were constructed to full naval standards. All the classes were limited in effectiveness by their speed, which was no more than 20kts. This was adequate when faced with opponents whose submarines could barely exceed 7kts or 8kts submerged and the ‘Loch’ class in particular were very efficient submarine hunters. The enemy, however, was changing, for in 1944 production was underway in Germany of the Type XXI ocean-going U-boat and the Type XXIII coastal boat which were capable of 17kts and 12.5kts submerged respectively. Also planned by Germany were the ‘Walter’ Type XXVI boats which were designed to achieve 24kts underwater using a newly-developed HTP turbine. These developments made the entire vast escort fleet potentially obsolete.¹

Even before the new German threat was known, in the summer of 1943 the Allies were working on a standard class of escort vessel which could be produced in both Great Britain and the United States. The aim was to give the best surface and anti-aircraft protection possible to convoys without prejudicing the endurance and anti-submarine requirements. The main improvement over existing designs was an increase in speed to 24kts through the use of more powerful geared-turbine machinery. It was anticipated that displacement in trial condition would have been about 1700 tons. The gun armament was to be two twin 4in mountings forward with two twin 40mm ‘Buster’ and either six or eight 20mm Oerlikons. The antisubmarine armament was to be an as then unspecified ahead-throwing weapon. By August 1943, with the U-boat threat under control, the project died as there were other more urgent production requirements. This project, although not pursued, does give us a small window on the way that anti-submarine frigates were going to develop.²

By December 1944 a need for new sloops was becoming apparent. It was clear that a new design was needed and the first attempt was essentially a Black Swan class sloop redesigned to be capable of 25kts. Displacement went up to some 1660 tons full load from the 1429 tons of the 1944 version of the class, and the shaft horsepower rose from 4300shp to 15,000shp. In January 1945 it was realised that anti-submarine and anti-aircraft versions were going to be needed for convoy protection and the frigate and sloop types then began to converge. The main armament considered for the anti-aircraft version was either two twin 4.5in or three twin 4in mountings. The anti-submarine version was to carry a gun armament of either one twin 4.5in or two twin 4in mountings. The 4.5in option, however, was preferred, as this gun was destined to become the standard high angle/low angle gun in the future; it also had the advantage of an enclosed turret whilst the open-backed twin 4in Mark XIX was then considered to have reached the limit of its useful development. By the end of the month Staff Requirements were being considered, one of which was to limit displacement to 1400 tons. The Director of Naval Construction did not consider this constraint feasible. It was also indicated that the ships should be capable of mass production and that the hulls should be interchangeable and possible to complete as either anti-submarine or anti-aircraft vessels.

By the end of February it was accepted that the antisubmarine version would displace some 1560 tons whilst the anti-aircraft escort would displace 1650 tons. At this time the incorporation of aircraft direction facilities in the anti-aircraft version was considered but ruled out in view of the loss of armament. By the end of April 1945 it was confirmed that the versions considered in February should proceed. It was also now concluded that an aircraft-direction version was indeed needed and that a further version, ‘A Headquarters Ship for the Senior Officer of a Convoy Escort’, was also a requirement. The increase in size and complexity of the new escorts meant, however, that it would not be possible to produce the new ships in sufficient numbers. This was to lead to thinking that corvettes would still be required and it was decided that a separate design for this type of ship should be begun. This will be considered later.³

The end of the war resulted in a reappraisal of the planned 1945 New Construction Programme. The Programme, which originally incorporated plans to build four of the new escorts, was scaled down to just two ships for financial reasons, one to be an anti-aircraft version, the other an anti-submarine ship. The Cabinet approved construction of the new frigates in November 1945. There was soon a further debate amongst the Naval Staff as to which type of frigate should be built. The conclusion was that one anti-submarine and one aircraft-direction frigate should be constructed, the aim being to lay the ships down in 1946. The designs of the frigates were far from settled at this point in time and by January 1946 the displacements were increasing, that of the anti-aircraft frigate rising to 1750 tons mainly due to an increase of 50 tons in the weight of the machinery. This development gave rise to the possibility that two designs would give better-balanced ships with the anti-aircraft and aircraft-direction versions being capable of 20kts whilst the anti-submarine and Senior Officer Convoy variants retained the 25kt speed requirement. At this time the suggestion was not implemented as there was still a desire to retain the standard hulls with their consequent production flexibility. The theory was that an anti-submarine, anti-aircraft or aircraft-direction version could be produced at a late stage in construction to meet the most pressing need. In practice the designs, although theoretically capable of mass production, were becoming very complex, with the result that any change would not be easy to achieve unless demanded at an early stage in construction.⁴

In March 1947 the need for standardised hulls for all versions was again being questioned. It was decided that the anti-aircraft and aircraft-direction versions should use diesel machinery in order to achieve the Staff Requirement for an endurance of 4500 miles at 15kts, which current designs of steam machinery could only achieve if the weight of machinery and fuel were increased by 800 tons. A subsidiary reason was the limited capacity available to produce steam turbine sets within the United Kingdom should quantity production be wanted. By April a revised hull design for the two diesel-powered frigates was underway. These became the Leopard and Salisbury classes.⁵

The number of frigate designs under development or evolving was ultimately to lead to the Admiralty instituting a system of Type Numbers, which came into practice in July 1950. It was clearly becoming difficult to differentiate between the various designs, some of which had rather clumsy titles. What became the Type 18, for example, had been simultaneously referred to as ‘The improved limited conversion’ and ‘The fused conversion’. Clearly something had to be done to rationalise the titles. All ocean convoy escorts, including converted destroyers, were to be known as Frigates, which in turn were divided into antisubmarine (Type 11 and following), anti-aircraft (Type 41 and following), and aircraft-direction (Type 61 and following). An Admiralty Fleet Order defined multi-role ships as destroyers if they could attain fleet speed, or sloops if they were slower.⁶

Salisbury, first of the Type 61 aircraft-direction frigates, in November 1956. Note how radar and sensors dominate the upper deck layout. The low air-warning radar Type 960 is located aft of the second combined mast and funnel.

(D K Brown collection)

The Anti-Aircraft and Aircraft-Direction Frigates (Types 41 and 61)

These two classes were the first post-war frigates to be designed in detail and their development was to run in tandem. Legends were prepared in December 1947. The anti-aircraft version displaced 1770 tons, whilst the aircraft direction version displaced 1665 tons. The armament was as anticipated – the anti-aircraft version mounted two twin 4.5in Mark VI, the aircraft-direction type having one such mounting and a much more comprehensive air-warning radar system in place of the second. The 4.5in gun was, however, regarded as an interim fitting for it was anticipated that in due course the new twin 3in/70 cal. mounting then under development would be carried in all the planned new frigates when the Stage II equipment option was implemented. It was to be January 1955 before this plan was finally abandoned.⁷ The anti-submarine weapon was a single Squid with 10 salvoes carried.

It was initially considered that these frigates would be produced in large numbers in wartime but the nature of the hull construction and the elaborate electrical equipment meant that this aim would just not be met. The hull was constructed using a large number of longitudinals in the hull structure, a technique introduced after explosive tests against the hull of the Nonsuch (the ex-German destroyer Z38). The structure was designed by E W Gardiner, who had carried out these trials. Although effective, the technique gave the shipbuilders considerable difficulty in constructing the vessels. A high degree of standardisation was achieved in the two classes, with the engine installation and the hulls being identical. However, the engine installation was complex, involving the fitting of eight ASR 1 diesels driving two shafts. A three engine-room arrangement was adopted, with the first and third engine-rooms each containing two more ASR 1 diesels driving generators. The main engine exhausts were originally to lead through the ship’s side at the waterline but technical considerations meant that this idea was dropped in 1951. The ASR 1 design evolved from a high-speed V16 diesel for submarines, the prototype of which was under construction at Chatham in 1939. It was further developed in 1941 and it was initially intended to install the design in the new ‘A’ class submarine. The idea did not progress and the plan lapsed, but the design was not abandoned and shortly after the war it was converted to direct injection and supercharged, becoming the ASR 1 prototype.

The new diesel installation was 100 tons heavier than the steam plant which was first considered, but the major gain achieved by the diesel engine over the steam turbine was in endurance, where the anti-aircraft version could achieve 4500 miles at 15kts whilst the aircraft-direction frigate achieved 5000 miles at the same speed, the difference being due to the ability of the latter type to carry more fuel because less space was taken up by armament and ammunition. The ship was also slightly lighter in displacement. One weakness was the lack of speed, performance being below that needed for both classes to operate as effective units of the fleet, but then they had been conceived as convoy escorts. The distinctive forecastle was an aid to improved sea-keeping in a design where there was a need to keep the heavy forward 4.5in mounting low in the ship. A small 60kW generator was also fitted in the eyes of the ship, as far as possible from potential harm. Both designs carried a comprehensive radar fit, each having the Type 275 anti-aircraft fire control and Type 960 air-warning radar. The Type 41 frigate also carried the Type 262 close range anti-aircraft control system and the Type 992Q surface/low level search system, reflecting its anti-aircraft role, while the Type 61 frigate was fitted with Type 277 height-finding, Type 960 air-warning and Type 982 low air-warning radar for its specialised task. Each class was fitted with Types 162,170 and 174 sonar. In June 1950 Legends of both types were again prepared, the Type 41 being 1835 tons standard, the Type 61 displacing 1738 tons standard. Growth from the displacement calculated some 2½ years earlier was relatively modest as the detailed design evolved.⁸

The prototypes were ordered from Portsmouth (Leopard) and Devonport (Salisbury) Dockyards, a decision made as early as January 1948. Arrangements were also then being made to order the engines, a task which the Engineer-in-Chief found difficult. The numbers of each class planned varied from year to year, the requirement being eleven Type 41 and ten of the Type 61 in early 1953. Ultimately only four vessels of each class were built for the Royal Navy, with a further three Type 41 frigates being purchased by India, one of which was originally intended for the Royal Navy.⁹ The time taken to build the ships was prolonged, ranging between 3½ years and 6 years, reflecting deliberate delays to constrain costs in given financial years, and design complexity. The ships were also competing for resources with the merchant ship owners and other major industries in an era of full employment. Both classes proved to be dead ends in design evolution, for no further frigates using diesels solely for propulsion were produced for the Royal Navy with the exception of Mermaid, a design based on the Type 41 but with a far weaker armament, the main offensive weapon being a twin 4in Mark XVI. This vessel was ordered by Ghana as a presidential yacht and laid down in 1965 but the contract was cancelled following a change in government. The ship served in the Royal Navy for only some 4 years before being sold to Malaysia.¹⁰

Lynx, Type 41 anti-aircraft frigate, in May 1957. The ship is dominated by the two twin 4.5in Mark VI mountings.

(D K Brown collection)

The Anti-Submarine Frigate (Type 15)

The first thoughts on converting ‘Emergency’ wartime destroyers into anti-submarine escorts emerged in March 1947, but it was quickly decided to wait until experience had been gained with the new ‘Weapon’ class anti-submarine destroyers before deciding how best to evolve the design. By November 1948 design work was given high priority on both this and also a simplified version which was being developed in parallel. Ten ships of both types were initially envisaged. The destroyers Rocket and Relentless were selected to be Type 15 prototypes, the functions of the type being to protect convoys of all types against submarines and to hunt and destroy submarines in cooperation with aircraft.¹¹

By 1949 the international political situation was deteriorating and it was clear there would be a severe shortage of anti-submarine frigates capable of dealing with fast submarines such as the Russian ‘Whiskey’ class, and that it would not be possible to remedy this shortage by building new frigates. There were, however, considerable numbers of the wartime ‘Emergency’ class destroyers whose armament was outdated but with sound hulls and machinery. The programme now expanded to make use of these assets. The proposed armament was to be double Squid ASW mortars sited on the after deckhouse. In the event the prototype Limbo was installed in Rocket and Relentless, with Squid carried later on an interim basis in sister-ships until Limbo, as the Mark X was in production. Eight (the original Staff Requirement asked for twelve) antisubmarine torpedoes, the ‘Bidder’ (Mark XX), were carried and it was proposed that four tubes be fitted for launching them. The original proposal was for reloads to be held in a centreline deckhouse, but this lead to reloading problems. There was also concern over the drop from the forecastle deck level to the sea, but this was overcome. Eventually, eight single tubes were fitted (no reloads) but few ships carried the system and eventually the ‘Bidder’ was dropped. The supporting sonar sets were Type 170 and 174. The main gun armament, the twin 4in Mark XIX controlled by a CRBF director, was sited aft instead of on the forecastle where it would have obstructed the view from the new low bridge structure and would also been very exposed when the ship was driven into head seas. Also carried was a twin 40mm Bofors Mark V controlled by a ST director. This armament seemed light but it weighed considerably more than the original destroyer fit (179 tons compared to 150 tons). Space was also needed and weight-saving, particularly high up, was clearly important. Some thought was also given to fitting ‘Fancy’, an anti-surface ship HTP torpedo, but this idea died as did the weapon itself.

Assistant Director N G Holt was instrumental in the design, incorporating an aluminium forecastle extended well aft, a very brave decision as it involved manufacturing what was probably the largest aluminium structure afloat. The design of the structure was comparatively straightforward but, because of the low modulus (load/extension) of aluminium, the design was governed by deflection rather than stress. The connection of aluminium to the existing steel structure was a potential problem due to the danger of electrolytic corrosion. The scheme adopted was to weld a steel bar flat to the deck and then bolt or rivet the aluminium to it using insulating material between the two metals. There seem to have been no problems in service.

Rocket, the prototype Type 15 full conversion, in July 1951. Trials with the ex-German destroyer Nonsuch (Z38) suggested that the spray deflector on the side near the bow helped to keep the forecastle dry. A similar deflector was fitted to Rocket, as shown here, but no benefit was found and no other ships were fitted.

(World Ship Society, Abrahams Collection)

A big operations room stood on 1 deck; there was no bridge in the conventional sense as the captain was expected to handle his ship from the operations room – he was given a periscope with which to see out – but the last three ships had a small bridge over the operations room. At the fore end of the superstructure on 1 deck there was a steering position with big windows. Unfortunately, no model tests were carried out to assess the viability of this feature in all weathers, and they turned out to be obscured in any sea. The big openings in the keel for sonar domes were a problem, as structural theory of the day could not cope, but ‘engineering judgement’ produced an effective solution. Fore and aft access under cover proved a major advance in comfort, and hence efficiency, for the crew, who no longer had to cross an open deck in heavy seas and risk a soaking.

Altogether twenty-three Royal Navy destroyers were converted, twelve in Dockyards, the rest in commercial yards. Four Australian and two Canadian destroyers were also converted on similar lines. A conversion took about 2 years and although the initial cost estimate at £600,000 seemed excessive at the time, they were amongst the best anti-submarine ships in the world and most had service lives of 15 to 20 years after conversion.¹²

Teazer, a Type 16 limited conversion, in May 1955. The ship retains one set of torpedo tubes which were pertinent to the ship’s previous role as a destroyer. Note the Squid antisubmarine mortars sited on the deckhouse aft of the torpedo tubes.

(D K Brown collection)

The Aircraft-Direction Frigate (Type 62)

This proposal first emerged in August 1948, the basis being the conversion of an ‘R’ class destroyer. The radar installation initially planned was Type 293Q, two Type 277Q, Type 960 and two Type 262. Armament comprised a twin 4in mounting, a twin 40mm Bofors, and a single Squid. By September 1949 the programme was to start with the conversion of the five surviving ‘M’ class destroyers at a cost of some £386,000 each. The class title at this time was ‘Aircraft Direction Frigate Limited Conversion Fleet’. The allocation of a Type number was a very necessary simplification.

By December 1951 the radar outfit had been modified. It now consisted of Types 293Q, 960, 974, 982 and 983. The prototypes were to be Marne (‘M’ class) and Myngs (‘Z’ class), which were to be followed by the four remaining ^CM’ class and the intermediate destroyers Kempenfelt, Troubridge, Wager, Whelp, Savage and Ursa (substituted for Grenville). The intermediate destroyers, however, could not mount the Types 982 and 983 radar wanted in the revised design so they were eliminated from the Type 62 Programme. The 1954 Radical Review resulted in the deletion of four of the ‘M’ class conversions, leaving just Musketeer in place as a potential prototype. However, Salisbury (Type 61) was expected to be ready by September 1955 so, with no need for Musketeer as a trials ship, it was decided that it was not economic to proceed with her conversion.¹³

The Anti-Submarine Frigate (Type 16)

This class was a simplified conversion of wartime destroyers to anti-submarine convoy escorts. Development evolved in parallel with the Type 15 and initially ten vessels were to receive the limited conversion, the aim being that they should follow the first ten destroyers receiving the full conversion. At one stage eighteen conversions were said to be planned. The Staff Requirement was exactly the same as that expected of the full conversion but inevitably the capability was to be less. The basic destroyer hull outline was retained but there were modifications made to the bridge structure so that AIO compartments, radar offices and a closed navigation bridge could be provided. The fore end of the hull was fitted with additional stiffening so that the ship could be driven into head seas. A twin 4in Mark XIX was originally to be mounted in ‘A’ gun position, but this position was later altered to ‘B’ position, which reduced exposure in heavy seas. A twin 40mm Mark V mounting was also to be carried, but this was replaced by five single 40mm Bofors Mark IX mountings in the final design; on completion most carried one twin Mark V and three single Mark IX 40mm Bofors. The Type 293 target indication radar was installed. The anti-submarine armament consisted of a double Squid capable of firing 20 salvoes, 120 projectiles being carried. It was also planned to mount four anti-submarine torpedo tubes without reloads but these were not installed and four of the 21in torpedo tubes, which the class carried as a destroyer, were retained. A Type 170 attack sonar and a Type 174P medium-range search sonar were fitted.

The prototype conversion was Tenacious and ultimately six further units of the ‘T’ class emergency destroyers received the limited conversion. Also converted were one ‘O’ class and two ‘P’ class destroyers, which made up the full complement of ten conversions originally planned. The ‘O’ and ‘P’ classes had less endurance than their near sisters: 1700 miles as against 3000 miles at 20kts. The cost of a ‘limited’ conversion at £260,000 was considerably less than the £600,000 price of the full conversion. The other advantage was that theoretically a destroyer could be modified in 10 months as against the 18 months budgeted for a full conversion, an important consideration in the early years of the programme. The weak link was a relatively poor anti-submarine armament and once production of the full conversions was coming forward there was no need to convert any further limited versions beyond those planned, for which equipment had been procured.¹⁴

The Anti-Submarine Frigate (Type 12)

Up until the end of 1947 the anti-submarine frigate was still expected to achieve a speed of 25kts with 20,000shp, with endurance of 3000 miles at 15kts. But by early 1948 the Naval Staff Target had changed, with a speed of 27kts and endurance of 4500 miles at 15kts now wanted. The threats to be coped with were now threefold. First, the typical Second World War submarine with an underwater speed of 7kts, the answer to which was the ‘Loch’ class. Second, an enemy equivalent of the Intermediate ‘B’ Type Submarine (Porpoise class) capable of 17–18kts, requiring a 27kt frigate to counter it. Third, there was also the HTP submarine able to achieve 25kts underwater: two boats of this type, Explorer and Excalibur, were being designed for the Royal Navy and the Russians also had access to German HTP technology. A 35kt ship was needed against such submarines. It was to take more than 10 years to overcome a threat with this speed, shipborne helicopters providing the answer. By the end of the year the Board of Admiralty had sanctioned development of the upgraded design to cope with the Intermediate ‘B’ Type threat.¹⁵

Initially work on the design was slowed by a lack of staff, priority being given to designing the conversion of destroyers into anti-submarine frigates. Indeed, at one time there were thoughts of postponing the first-rate design for 5 years in favour of a less-capable version, but this idea was ruled out. By February 1950 the Sketch Design was ready for approval by the Board of Admiralty. The standard displacement had risen to 1840 tons whilst the engines now produced 30,000shp using the new Y100 steam turbines. A compromise had to be made with the endurance. Instead of achieving 4500 miles at 15kts, this could only be achieved at 12kts. Initially the main antisubmarine weapon was to be a double Squid but by the time the design was placed before the Board of Admiralty the double Limbo had been substituted. There were also to be anti-submarine torpedoes, but these had not yet been developed and ultimately they proved a failure. The gun was the twin 4.5in Mark VI as long planned, but provision was made for fitting the new 3in/70 cal. mounting. The initial radar fit was to be Type 277Q for height finding and Type 293Q for target indication. Also fitted in service were Type 262 for close-range anti-aircraft fire control and Type 275 for long-range anti-aircraft fire control. The sonar sets mounted were Types 162, 170 and 174, the latter set being later replaced by Type 177.

Torquay (Type 12 first-rate anti-submarine frigate) in August 1956. Note the small cylindrical funnel which was designed to resist a nuclear blast; this was later replaced with a larger, domed design.

(D K Brown collection)

The funnel was originally designed to resist a nuclear blast but it was later considered ugly and replaced. According to Arthur Honnor RCNC, the hull design was simplified in that the number of longitudinals was reduced when compared with the earlier anti-aircraft and aircraft-direction designs. The hull form developed by N G Holt and R W L Gawn incorporated a high freeboard carried aft, a deep draught and fine lines forward which gave a centre of buoyancy well aft (see photographs of Leander and her model in Chapter 12). To maintain stability as fuel was consumed, water ballast tanks were fitted under the fuel tanks, water being admitted via an elaborate system of pumps as fuel was used up. The utilisation of these features was based on practical experience at sea and an extensive series of tests by Gawn at the Admiralty Experiment Works, Haslar.

The refitted Type 12 Rothesay, seen here modernised to Leander standards. The helicopter deck to operate a Wasp helicopter (which displaced one anti-submarine mortar), a hanger for the helicopter and a Sea Cat short-range missile system in the place of a 40mm Bofors are clearly visible.

(D K Brown collection)

Rothesay in 1960 as originally completed, first of the second group of Type 12 frigates. The main visible difference from the Whitby class was the larger funnel. They were fitted for the Sea Cat short-range missile system, but carried a 40mm Bofors mount in lieu until refitted later in their careers.

(World Ship Society)

An overhead view of Torquay (Type 12 first-rate antisubmarine frigate) in August 1956. Note the fine bow lines. There are chocks amidships for the single AS torpedo tubes that were only fitted in a few of the class.

(D K Brown collection)

A conspicuous feature of the Type 12 frigate, and to some extent of the Types 41 and 61, was the raised fore end. The fine lines forward in the Type 12 hull form could only accommodate the large-diameter gun bay of the twin 4.5in Mark VI gun bay if this installation was placed well aft. This in turn forced the bridge further aft than was usual. The Mark VI turret was both high and heavy and to enable watchkeepers to see over it the mounting was placed as low as possible in the ship, which assisted stability. With the bridge forced into the low-motion zone amidships, watchkeepers were given an easy ride, accounting for some of the reputation of the class as good sea-boats. The Type 41 and 61 classes had fuller lines, but it was still desirable to keep the Mark VI turret low and they were given a similar profile. It was widely believed that this peculiar profile accounted for their good seakeeping qualities and in particular keeping the deck dry. The ideas were translated to the Type 23 frigate in a modified form by D K Brown at the concept design stage, the aim being to maintain the maximum freeboard a little aft of the stem as there is evidence that waves come over the deck in that position. In the Type 12s the raised fore end was a convenient place for the diesel generators, as far as possible from the turbo generators, good practice for damage limitation. Unfortunately, because the diesel exhaust made the paint dirty; they were moved in the Leanders so that they could exhaust up the mast, which Brown considered a retrograde step.

The Type 12s and later twin-screw frigates had twin rudders in the propeller slipstream for improved performance, giving a turning circle of about 3½ times the ship’s length. Also incorporated were slow-running 12ft propellers, which revolved at 220rpm instead of conventional destroyer propellers of 10ft 6in diameter. This feature was eventually to contribute to the quiet speed being virtually doubled.¹⁶

Soon after the Board of Admiralty approved the Sketch Design the class was described as the ‘Type 12 Anti-Submarine Frigate First Rate’. Six frigates were produced to the original design, the Whitby class, and nine slightly modified versions, the Rothesayclass, for the Royal Navy. In addition, two were built for India, which were originally intended for the Royal Navy, three for South Africa and a further four were constructed in Australia. The external differences between the two groups were small, the main gain in the Rothesay class being the ability to fit Sea Cat. The cruising turbines were also eliminated, which reflected the increased use of the ships with the fleet rather than as convoy escorts as originally planned. The Rothesay class were all later rebuilt to Leander standards, but the original six Whitby class were little changed throughout their lives apart from much of the thin hull plating having to be replaced due to corrosion.

The Anti-Submarine Frigate (Second-Rate) (Type 14)

The role of the second-rate frigate during the war years was performed by the ‘Flower’ and ‘Castle’ class corvettes. With new threats appearing it was concluded that a new corvette design was needed. A study made in June 1945 resulted in a vessel displacing about 1000 tons armed with a single 4in gun, one twin 40mm Bofors and four twin 20mm Oerlikons. A twin Squid with 20 salvoes was provided, together with 15 depth charges. Speed was 20kts with the endurance sought being 4000–5000 miles at 15kts. No development seems to have taken place beyond the production of this brief outline and with the cessation of hostilities the idea was dropped.¹⁷

A new intermediate anti-submarine frigate was considered in March 1947 when there seemed to be possibilities that the first-rate vessels would be delayed. There was a resemblance to the vessels built later in that they were steam-driven with a strong anti-submarine armament and light surface weaponry. However, this was an idea which again quickly died. In October 1948 there were ideas that that an anti-submarine frigate could be produced with ‘Hunt’ type machinery, but studies soon showed that this proposition was ineffective and again the idea was dropped.¹⁸ The summer of 1949 saw a need for a second-rate frigate again emerging, this time the aim being to increase numbers without increasing costs. Initial thoughts veered towards a diesel version, but this was ruled out because of cost, with the result that half the installed power of a first-rate frigate became the only option at this time. The ships again concentrated on the anti-submarine role through the double Limbo and anti-submarine torpedoes supported by the best asdic (sonar) sets available at the time. The sonar outfit was the equal of that mounted in the Type 12 class. The anti-aircraft armament was originally to be one twin 40mm Bofors mounting located on the bridge structure, and one single. Tests at the Admiralty Experiment Works, Haslar, however, indicated that such an arrangement was not satisfactory and ultimately three single 40mm Bofors with a simple form of direction were fitted.¹⁹

Type 14 second-rate frigate. Preliminary Sketch Design produced in August 1949. The outline of the final design can be discerned but the funnel is raked and there is a Bofors mounting on the superstructure.

(Drawing by Len Crockford from original in NMM DNC Records)

The Type 14 second-rate anti-submarine frigate Keppel in June 1956. The AS Mark X mortars aft dominate the armament, and despite their reputation for being ‘under-armed’ in terms of weight the weaponry (including the sensors) was heavy for a ship of this size.

(D K Brown collection)

Building times were meant to be a mere 3 months longer than seen in the Second World War when the ‘Flower’ class were in production. The new design was, however, far more complex than the wartime vessels and most of the twelve vessels (the Blackwoodclass) built for the Royal Navy took over 3 years to complete. Structurally the class proved rather frail and they needed considerable strengthening, particularly after fishery protection duties in Icelandic waters. They also had problems at the break of forecastle where there was a two-deck step which caused a major stress concentration. They were also prone to slamming under the flat stern in following seas. The Type 14 had a big single rudder behind its single propeller. The rudder could not be removed on normal dock blocks so the lower part was separate and could be removed before docking. The problem with this attachable piece was that it often fell off at sea and it is believed that it was often not replaced. The ‘Tribal’ class tried to overcome this problem by fitting two large rudders close to each other. It was also hoped that this pair of rudders would channel the propeller slipstream and aid turning at rest. Experiments were run with rudders turning through 45° and with flapped rudders in which the after portion moved through double the angle of the forward section.

The accommodation was also rather sparse and 50 per cent hard-lying money was paid to crews when they were on fishery protection duty. The Ships’ Names Committee originally considered names such as Cromarty Firth and Dornoch Firth for the class following the Second World War tradition, but the idea was quashed within the Admiralty.²⁰ The ships were then named after famous naval officers. The Blackwood class proved to be very competent anti-submarine vessels, a reflection of their focused role.

The Type 11 Frigate

The nature of this design is one of those rather tantalising mysteries which gives rise to speculation. Logically it should have been the first of a line of anti-submarine frigates. Amongst ideas forthcoming, the most quoted version is that it was an anti-submarine version of the Types 41 and 61 with the same engines. However, such a ship would have been too slow for the task, less effective than the new second-rate design then being developed and as costly to produce as the first-rate frigate. It seems unlikely therefore that this arrangement was ever suggested.

Another possibility is that a frigate with ‘Deltic’ diesel engines could have been considered. A memorandum was presented to the Board of Admiralty in October 1950, close to the date when the Type numbers were instigated, which indicated that a ‘compounded’ version of the engine was to be developed. The note made the point that ‘this should give us 6000shp on an engine about the bulk of the First Lord’s desk’. Someone might have thought of using this engine in a frigate which with eight engines would have possessed sufficient power to counter any HTP submarines that the Soviets might possess. The speed of 35kts wanted for this task could have been achieved. However, the engine was destined for motor torpedo boats, and in a de-rated form, in the interest of a longer life, for coastal minesweepers. The new version was probably years away from production.

One final thought is that the first version of the Type 14 Blackwood class, which had some fundamental differences from the production version, may have been given the Type 11 designation. It was after all the submission of this design to the Board of Admiralty which caused the institution of the ‘Type’ numbering scheme which has survived for well over 50 years. No record has, however, been found.

It may well be that a Civil Service ‘quirk’ is the cause of no Type 11 appearing and that for some unexplained reason the number was not used. No evidence has been discovered to substantiate any facts which have appeared in print and no one alive who was close to the design process at the time has any knowledge which could lead to the mystery being solved.

The Third-Rate Frigates (Types 17 and 42)

In June 1950 with the international situation deteriorating it was decided that a truly austere vessel was needed which could be mass-produced. The first- and second-rate frigates, although initially planned for mass production, clearly could not be quickly produced even in wartime. Initial studies produced two diesel-powered options of 950 and 800 tons respectively. The larger ship carried a Limbo anti-submarine mortar and four fixed torpedo tubes. Four ASR 1 diesels gave a speed of 22kts. The second ship was even more austere, with an armament of one Squid and two anti-submarine torpedoes, whilst two ASR 1 diesels gave a top speed of only 19kts. Both carried a twin and single 40mm Bofors mounting.

Within 5 months there were calls for a gun-armed coastal frigate able to operate on the East Coast of the United Kingdom against both aircraft and fast attack craft, the requirement harking back to the days before the war when the ‘Hunt’ class were designed. Both designs were now developed in parallel, but progress was slow and it proved difficult to reconcile the two differing requirements. By late 1951 the machinery to be installed in the anti-submarine version, now designated the Type 17, evolved to a utility steam turbine installation with one shaft and one boiler, with displacement approaching that of the Type 14 frigate. The anti-aircraft version, now designated Type 42, had two shafts and two boilers. The main armament of the Type 42 was initially three 3in/50 cal. supplied by the United States. By January 1952 there were doubts about supplies coming from this source so it was decided to mount three single 4in Mark XXV. This gun was being developed by Vickers as a utility mounting which could be produced by engineering firms with no previous armaments experience.

Type 17 third-rate antisubmarine frigates. These two austere designs were produced in June 1950. They were effectively diesel powered and simplified versions of the Type 14, but with their slow designed speeds their effectiveness would have been questionable.

(Drawings by John Roberts from originals in PRO ADM 1/22001)

There were serious thoughts about building a prototype of each type under the 1954–5 Estimates but by late 1953 it was clear that there was no possibility of ordering the ships before December 1954. The designs were far from being ready, with Staff Requirements being revised yet again in the summer of that year. For example, various options for the Type 42 hull design were still being considered. The Ships’ Names Committee suggested new names in June 1953. For the Type 17 the ‘Firth’ names were revived, whilst it was suggested that the Type 42 be given names of precious stones, Agate, Amber, Jade and Topaz being four of twelve suggested. The Type 17 design reached the stage where it went to the Board of Admiralty but was stopped at that point before formal presentation. By the end of the year the decision had been made to abandon both types and also not to order any more of the second-rate Type 14, which was in production. It was, however, decided to develop new, less-constrained designs which emerged as the Common Hull Frigates (see below).²¹

The Anti-Submarine Frigate (Type 18)

This conversion was originally conceived in the summer of 1950 as a replacement for the Type 16 limited conversion, the origin of the project being the not-infrequently expressed dissatisfaction of the Naval Staff with the Type 16’s anticipated operational performance. The DNC was also not impressed with the limited conversions; he considered it wrong to waste valuable destroyer hulls and machinery on equipment which was inadequate to cope with modern submarines. By early 1951 it was suggested that this new class should replace both the limited and the full Type 15 conversions. The key improvement over the Type 16 was the mounting of the double Limbo anti-submarine mortar supported by a Type 170 sonar. The improved Type 177 sonar was to be fitted at a later date. The ship would also have a better anti-aircraft performance with the 4in twin mounting being controlled by the Close Range Blind Fire (CRBFD) system instead of the Simple Tachymetric Director (STD). This armament achieved virtually the same effectiveness as the full conversion, the only loss being the Type 277Q height finding radar and four anti-submarine torpedoes. The cost of the conversion was reduced from £600,000 to £400,000; in addition there was a saving of 3 months in conversion time – all useful gains.

In April 1951 the destroyer Noble was initially planned for the prototype conversion and it was expected that the remaining four ‘N’ class destroyers would follow. By July 1953 the programme had expanded, with Troubridge and Savage and four ‘Z’ class destroyers earmarked for conversion, with the remaining four ‘Z’ class also to be considered. None of these plans were to progress, for concern was expressed about the multiplicity of frigate types being built and converted and the Radical Review seems to have finally brought about this project’s demise.²²

The Common Hull Frigate

Following the demise of the Type 17 and the Type 42 frigates, the search for a cheap frigate to be built in numbers continued with a larger ship which could be completed with either anti-submarine or anti-aircraft armament, as with the wartime ‘Loch’ and ‘Bay’ classes. It was again intended to build a prototype of each variant, sort out any problems and prepare drawings for mass production should it be needed. The anti-aircraft version carried two twin 4in Mark XIX mountings, one twin 40mm Bofors and one Squid. The anti-submarine version had one Limbo and two twin 40mm.

The design, which was worked out in some detail, was loosely based on the Black Swan and looked attractive. However, it was becoming increasingly clear that the weapons and sensors were nearly obsolete and capability against both aircraft and submarines was limited. The final blow came with the explosion of the first hydrogen bomb, making mass production in war unlikely. The cancellation was followed by an interesting period looking for frigate designs which could be built in numbers and yet have a worthwhile capability.²³

The ‘Tribal’ Class Frigate (Type 81)

With the demise of the Common Hull Frigate the next idea to emerge was a ship with the capability of a second-rate frigate in all three main aspects – anti-aircraft, antisubmarine and aircraft-direction tasks. They were also expected to be valuable for Cold War ‘police’ duties. Since a frigate was defined as a single-role ship, this multi-role design was referred to as a sloop.²⁴ Initial studies carried two twin 4in Mark XIX mountings, one twin 40mm, a Limbo and anti-submarine torpedo tubes. For aircraft direction a US-supplied SPS 6C radar was to be fitted. The main gun armament was, however, wanted mainly for shore bombardment so the twin 4in were replaced by two single 4.5in Mark V. The radar was replaced by a British Type 965. Tartar anti-aircraft missiles and twin 3in/70 cal. were also considered.

Type 81 Sloop. This study from mid-1955 shows the ship as then perceived. She mounts two twin 4in Mark XIX, a Mark X antisubmarine weapon and there is no provision for a helicopter. Note the austere funnel design, as wanted by the DNC, Sir Victor Shepheard. The design changed soon after he retired.

(Drawing by John Roberts from original in PRO ADM 167/139)

Despite its old-fashioned appearance, the ‘Tribal’ class frigate had many technical innovations.²⁵ Foremost in these was the machinery fit – single-shaft steam turbine with gas turbine boost. The size of the steam plant was set by the requirement for astern power, which gave a rather bigger forward power than was needed. With surplus power the required top speed was easily achieved and it was decided to optimise the hull form for high-speed cruising at about 18kts. The maximum speed was 24kts when the ship was in deep condition and out of dock for 6 months. The form was a ‘low prismatic’ with buoyancy concentrated amidships and very fine ends, then believed (mistakenly) to improve seakeeping. The form selected was the cruiser Neptune, Design ‘Y’ (1945), itself based on the First World War light battlecruiser Glorious.

The hull structure used a novel approach by the American, Schade, in which for the first time the buckling strength of complete stiffened panels of plating could be considered.²⁶ The design philosophy was that it was inevitable cracks would start in a complex structure built under shipyard conditions but that careful design would ensure such cracks did not spread.²⁷ The original design had an aluminium superstructure. One study had all aluminium above 2 deck, which was finally dropped following gun-blast problems on the Type 15s.

To avoid vibration problems the mast had to have a natural vibration frequency clear of propeller blade rate and this posed a difficult problem in those pre-computer days.²⁸ This led to a very wide base to the mast – with one leg passing through the wardroom table in the initial designs. Because of the asymmetric machinery the layout was heavily constrained and it took a redesign of the whole forward half to separate mast and table. The upper deck was dominated by the firing trajectory of the anti-submarine mortar which stood on 2 deck in a well and this pushed the bridge forward. Although the overall motions of the ‘Tribal’ class were not different from those of the Leander, the forward position of the bridge gave much greater motions at the compass platform.

The ‘Tribals’ were the first class designed for bunk sleeping and to be fully air-conditioned. The cost was much greater than that of the successor design, the Leander class, even though they were quite simple ships. Only seven were built, a number dictated by the production of machinery where intricate licensing (and by implication contract) arrangements were involved. With considerable design effort having been put into the class the Controller also considered it uneconomic to stop at just four ships.²⁹ They were, however, a valuable addition to the fleet, since they provided experience in the operation of gas turbines in warships before the ‘County’ class destroyers and their successors came into service. They were regarded as successful and most had service lives of 20 years in the Royal Navy.

Model of an earlier stage of the ‘Tribal’ class Type 81 general purpose frigate. Note that there was then no provision for use of a helicopter, and twin 40mm Bofors mountings were fitted abreast the mast.

(D K Brown collection)

Ashanti, the prototype Type 81 general purpose frigate. The landing deck for the Wasp helicopter looks very constricted.

(D K Brown collection)

Euryalus (Type 12 general purpose frigate) in August 1969, showing the appearance of the early Leander class ships as completed. Later ships carried a Sea Cat missile launcher instead of the two single Bofors on the hangar roof. Note the well in the stern for the Type 199 Variable Depth Sonar.

(D K Brown collection)

The Leander Class Frigate (Improved Type 12)

This design was initiated in 1959 and was a development of the successful Type 12, which had then been in service for 3 years. The armament changes involved two Sea Cat launchers instead of the Bofors anti-aircraft armament, anti-submarine torpedoes reduced from the twelve sanctioned in 1950 to just four (which never seem to have been fitted), and one Limbo anti-submarine mortar instead of two. The most effective gain was the ability to operate a P.531 Wasp helicopter which could carry Mark 43 or 44 anti-submarine torpedoes. A Cast 1 variable depth sonar was specified (Type 199) and the newly available Type 965 air-warning radar, as fitted in the new ‘County’ class destroyers, was carried. The machinery arrangements were based on the installation fitted in the Type 12 but the cruising turbines were dispensed with, as seen in the Rothesay class. The ships were now regarded as fleet escorts rather than convoy escorts, the higher cruising speed required being beyond the range of the cruising turbines. The ships were now used as the outer screen of a fleet which had the aircraft carrier at its core and an inner screen of guided missile destroyers. The endurance was 4500 miles at 12kts in deep condition 6 months out of dock in temperate waters. Fuel stowage was increased to 450 tons, achieved by abolishing separate ballast tanks, the ballast being carried in the fuel tanks. This, however, opened up the possibility of pollution when ballast was ejected from the fuel tanks. Habitability was also improved, with air conditioning installed in the accommodation spaces whilst the bridge and operations room arrangements were improved. Diesel generators were moved from the eyes of the ship to a position where the exhaust was emitted through the foremast, but nevertheless the distinctive raised forecastle was retained. With the advent of this design it was decided not to build any more units of the ‘Tribal’ class. Another decision taken was to complete three of the Type 12 frigates already on order to the new design. The cost of these ships increased from £4.1 million to £4.2 million, the new ships being expected to cost £4.25 million.³⁰

A total of twenty-six Leanders entered service with the Royal Navy between 1963 and 1973. They were not built to a uniform design, the first sixteen ships having a 41ft beam, increasing to 43ft in the last ten. There were also differences in the machinery with Y100 being fitted to the first ten units, the next six ships having an improved version designated Y136, and the last ten the Y160 system, which incorporated further benefits gained from operational experience. All had a 440-volt AC electrical supply producing 1900 kW in early ships, which was increased to 2500 kW in later vessels. They were intended to serve three commissions with two short refits and then after 10 years have a major refit.³¹

Leander in 1973. The ship has now been rearmed with the Ikara anti-submarine system, shown being fired from its forward ‘zareba’.

(D K Brown collection)

Galatea, as an Ikara Leander, entering the frigate refit complex at Devonport. These huge covered berths were intended to facilitate the major reconstructions of frigates like those applied to the Leander class.

(D K Brown collection)

The Ikara Leander (Batch 1)

The Australian designed Ikara anti-submarine missile was originally to be installed in the Type 82 destroyers. The 1966 Defence Review, however, reduced the Type 82 class to just one ship, which meant that another ship had to be found if the capability of this weapon was to be retained. The initial plan was to fit the weapon in an ‘Ikara Destroyer’ but with priority given to the ‘Sea Dart Destroyer’ (Type 42) other vessels had to be found in order to expedite matters. Five ships were initially wanted and in 1967 a debate ensued over whether the last five Leanders then planned (FSA 41–45) or the first five ships due for a long refit should be so fitted. The cost of fitting the weapon in new ships was estimated to be £700,000. The additional cost of fitting the system in existing ships was initially estimated to be £1.5 million per ship, a figure reassessed in February 1968 at £1.05 million. It was decided that in spite of the additional cost it was better to install the system in the refitting ships on the grounds that Ikara could be deployed earlier and the number of ships with the system could be varied. There was, however, a price to pay, for the final new construction order for Leander class frigates was reduced from three ships to two.³²

The conversion involved the removal of the twin 4.5in Mark VI mounting and the associated MRS3 director. The Type 965 radar was also landed. In place of the gun a zareba and handling room were built forward of the bridge structure whilst the missiles with torpedoes fitted were stored in the magazine. They had an automated ‘Action Information Organisation’ (AIO), and new sonar and communications. The gun armament now comprised two single 40mm Bofors, whilst the anti-aircraft missile armament now comprised two quadruple Sea Cat launchers. Also included in the reconstruction were enhanced air conditioning, updated machinery converted to burn dieso in the boiler furnaces, all cables replaced, and accommodation brought up to the latest standards. Electrical power was enhanced with two 300 kW diesel generators replaced by two 500 kW units. A water-displaced fuel system was fitted to improve stability, a necessary feature as the stability of the class was always considered marginal and they never satisfied the new Royal Navy criteria in full. The Wasp helicopter was retained. Eight ships (Leander, Ajax, Galatea, Naiad, Euryalus, Aurora, Arethusa and Dido), were ultimately converted at Royal Dockyards between 1970 and 1978, the cost ranging between £7.6 million and £23 million, with the average time taken being about 3 years.

The Exocet Leander (Batch 2)

The next group of ships were fitted with the Exocet antiship missile instead of Ikara. A new anti-submarine torpedo was also fitted, together with a new ‘Computer Aided Action Information System’ (CAAIS). The anti-submarine mortar was removed, the well being plated over to give a larger flight deck and hangar to accommodate the Lynx anti-submarine helicopter. The Sea Cat armament was enhanced, with two quadruple launchers mounted on the hangar roof, and an additional one fitted forward of the Exocet on the forecastle. The pairs of Exocet launchers were angled outboard to port and starboard to prevent any conflict with this Sea Cat. The modernisation included improvements to air-conditioning, accommodation and the replacement of all cables and was very much in line with the improvements worked into the Ikara Leanders. It was originally intended that eight ships would be converted to this standard but the programme was cut back to seven (Cleopatra, Phoebe, Sirius, Minerva, Argonaut, Danae and Penelope), with the eighth ship Juno being converted to a navigation training ship at Rosyth Dockyard. The seven frigates remaining in the programme were in hand at Devonport Dockyard between 1973 and 1982 the cost ranging from £13.8 million to £47.7 million, the average time taken being 2½ years.

The Sea Wolf Leander (Batch 3)

The last ten ships had a wider beam and thus improved stability which enabled the Sea Wolf point defence antiaircraft missile and Type 2016 sonar to be installed in addition to Exocet. There were still weight constraints and the funnel caps on this group had to be removed to improve margins. It was also estimated that 45 tons of paint (up to 80 coats) was removed, further increasing the stability margin. All ten of the group were originally to be rebuilt but costs escalated still further, now coming out at between £60 and £79.7 million. The programme started in March 1978 and was finally completed in December 1984, the time spent on each ship varying between 3 and 4 years. The result was that only the first five were converted, the remainder of the programme being cancelled under the terms of the 1981 Defence Review.³³ The five ships converted were Andromeda, Charybdis, Jupiter, Hermione and Scylla. Their unconverted sister ships Bacchante, Achilles, Diomede, Apollo and Ariadne were all sold for further service with the navies of Chile, Pakistan and New Zealand between 1982 and 1992.

The class proved to be one of the most successful designs produced for the Royal Navy. The production run was longer than desirable as it proved difficult for the Naval Staff to agree on a successor as the Type 22 fit required a much bigger and costlier ship. Additional ships were built for Australia (2), Chile (2), Holland (6), India (6) and New Zealand (2).

Whether the conversions, where costs escalated far in excess of inflation as the programmes progressed, were worthwhile is open to debate. The major gain was that by using existing ships it was possible to get new weapons to sea far more rapidly than would have been the case had new construction been relied upon, and several played an important part in the Falklands War. They were undoubtedly expensive, approaching the cost of a new ship with similar capability. The work was also difficult, because the class had been built before modern corrosion protection was developed and a great deal of structural renewal was needed before work could begin. Cleopatra, for example, needed 85 per cent of her keel replacing. Painting was also a particular problem: the shallow fuel tanks had to be grit blasted before high-duty epoxy paint was applied. It was a difficult and unpleasant task, as D K Brown discovered by venturing inside one tank while the work was going on. He was, however, pleasantly surprised by the standard of workmanship attained. The paint had to be used within 8 hours of mixing and its fumes were toxic and flammable so that work in adjoining areas had to be interrupted. Renewing the chlorinated rubber paint in the machinery spaces was nearly as difficult. All these complications contributed to the decision to curtail the major conversion and reconstruction programmes.

Minerva, a Leander class Type 12 Frigate in April 1979 rearmed with Exocet missiles in place of the twin 4.5in Mark VI mounting.

(Mike Lennon)

Andromeda in April 1981, rearmed with Sea Wolf and Exocet guided missiles.

(Mike Lennon)

¹ The design history of the German U-boats is admirably told in Eberhard Rossler, The U-Boat (London 1981). A prototype ‘Walter’ U-boat (Type XVIIB), U1407, was commissioned for trials by the Royal Navy and named Meteorite.

² ADM 1/13479: Standardisation of Escort Vessels (PRO).

³ ADM 138/830: Destroyers and Frigates General Cover (NMM). The Draft 1945 New Construction Programme included four vessels. By the end of June the Programme had been printed for presentation to the War Cabinet. Approval was sought to proceed with the design of four escort vessels of a new type, each of about 1400 tons with a speed of about 25kts. They were described as largely for experimental purposes, with two to be finished as AA ships and two as AS vessels. (CAB 66/67, PRO).

⁴ ADM 138/830 (NMM). Details of the 1945 Programme are set out in CAB 129/4 (PRO). The two escorts sanctioned ultimately appeared as the AA frigate Leopard and the AD frigate Salisbury.

⁵ ADM 138/830 (NMM); and Director of Naval Construction Correspondence Files – memo by Engineer-in-Chief, 21 July 1949 (NMM).

⁶ ADM 167/135: 1950 Admiralty Board Minutes and Memoranda (PRO).

⁷ ADM 138/795: 1945 Frigates AA and AD Types (NMM). The Legends are recorded in Naval Construction Department Records (NCD 24, NMM). Machinery for one AA and one AD frigate was ordered from Vickers Armstrongs (Barrow). One set was subcontracted to Peter Brotherhood, Peterborough. (ADM 138/795, NMM).

⁸ ADM 138/795 (NMM); and ADM 167/131: 1948 Admiralty Board Memoranda (PRO). A memorandum concerning prefabrication of frigates and the elaborate electrical equipment was written by a Deputy Director of Naval Construction in 1951. Arthur Honnor RCNC commented on the difficulties experienced by the shipbuilders in a note to this author. He also commented on the relative unreliability of the diesel installations in service, perhaps countered by the gain in endurance, which gave a considerable advantage over steam turbine machinery. The ASR 1 teething troubles were overcome and the type proved very valuable until later commercial diesels became available. They are now well liked by the Bangladesh Navy. The early history of the ‘Muscovin’ V16 is recorded in ADM 265/1: Engineer in Chief – Miscellaneous correspondence 1938–1940 (PRO), and J.K.H Freeman, To Invent or Assess (1982), a history of A E L. The profile with maximum freeboard carried aft was thought to keep the ship dry. Opinions still differ on effectiveness, but D K Brown used the approach on the Type 23, although mainly for aesthetic reasons.

⁹ The difficulty surrounding the supply of engines is recorded in DNC Correspondence Volume 74 (NMM). The best source for the history of the warship building programmes in the post-war era is Eric Grove Vanguard to Trident (London 1987). Type 41 class AA frigates built for the Royal Navy were Leopard, Lynx, Jaguar and Puma. Type 61 class AD frigates were Salisbury, Chichester, Lincoln and Llandaff. The Type 41 frigate Panther was sold to India before completion. Two further vessels of this class were built for India. Further names suggested by The Ships’ Names Committee were Cougar and Cheetah. Three Type 61 class frigates planned were named Coventry, Exeter and Gloucester. Other names suggested by the Ships’ Names Committee were Truro, Winchester, Durham, Ely, Lichfield, Armagh and Canterbury (Minutes are held in the Naval Library, Whitehall).

¹⁰ Conway’s All the Worlds Fighting Ships 1947–1995, pp516–17.

¹¹ DNC Correspondence Volume 72 and Volume 76 (1) (NMM); and ADM 167/133: 1949 Board of Admiralty Memoranda (PRO).

¹² ADM 167/133: 1949 Admiralty Board Minutes and Memoranda (PRO). The design of the structure was by Norman E Gundry, then Assistant Constructor, whose assistance in the preparation of this section is gratefully acknowledged.

¹³ ADM 138/798: Aircraft Direction Frigate Conversions (NMM).

¹⁴ ADM 167/133 and/135: 1949 and 1951 Admiralty Board Minutes and Memoranda (PRO).

¹⁵ ADM 116/5632: Ship Design Policy Committee (PRO). Asdics at the end of the Second World War were inefficient above 18kts.

¹⁶ ADM 167/135: 1950 Board of Admiralty Memoranda, ADM 281/149: 1950 Director of Naval Construction – Progress Report (PRO); and A Century of Naval Construction by D K Brown. The ‘Tribal’ class had to have the bridge placed further forward, which resulted in these ships giving a rough ride. The first production propeller designed by Honnor was known as C256, Brown was the trials officer. Quiet propellers were previously effective at 6 to 8kts.

¹⁷ D K Brown, ‘The 1945 Sloops – Designer’s View’, Warship World Vol 3, No. 3.

¹⁸ ADM 138/830: Destroyers and Frigates General Cover (NMM); G L Moore, ‘The Blackwood class Type 14’, Warship 2001–2002

¹⁹ ADM 167/135: 1950 Board of Admiralty Memoranda (PRO).

²⁰ Ships’ Names Committee Minutes (Naval Library, Whitehall). Other names suggested were Beauly Firth, Moray Firth, Pentland Firth, Solway Firth, and Westray Firth.

²¹ This account is based on G L Moore, ‘The 1950s Coastal Frigate Designs for the Royal Navy’, Warship 1995. Other names suggested were Cairngorm, Coral, Cornelian, Crystal, Jacynth, Opal, Sardonyx and Turquoise.

²² ADM 167/137: 1951 Board of Admiralty Memoranda (PRO); and ADM 138/810: Type 18 Frigate (NMM).

²³ This account has been provided by D K Brown, who worked on the project.

²⁴ Someone discovered that the Royal Navy had committed 70 frigates to NATO and to reach that number, the ‘Tribals’ had to be classified as ‘General Purpose Frigates, Type 81’, a contradiction in terms.

²⁵ There were a number of possible profiles pinned up in the design room and visitors were asked to vote on them. The Director of Naval Construction, Sir Victor Shepheard, reminded us that the team was not a democracy and duly told us his choice (D K Brown).

²⁶ This method was proposed by Ken Rawson, just back from an appointment with NCRE and writing a new structures course for the RN College. He used Schade’s graphs to re-examine the structure of wartime destroyers and showed the new method predicted problem areas better than the traditional approach (D K Brown).

²⁷ Examination of one ship towards the end of its life, after an exceptional wave impact, showed he got this right (D K Brown).

²⁸ It took D K Brown 3 months of difficult and tedious calculation and re-calculating existing masts to prove the method.

²⁹ ADM 167/146: 1956 Board of Admiralty Memoranda (PRO).

³⁰ ADM 167/157: 1960 Board of Admiralty Memoranda (PRO). Fowey, Hastings and Weymouth originally ordered as Rothesay class were built as Ajax, Dido and Leander.

³¹ D F Whittam RCNC and A J Watty RCNC, ‘Modernising the Leander class Frigates’, Trans RINA (1979).

³² DEFE 24/239: Ikara/Leander (PRO).

³³ Whittam and Whatty, ‘Modernising the Leander class Frigates’, Trans RINA (1979). The cost of the conversions is quoted in Richard Osborne and David Sowden, Leander Class Frigates (World Ship Society 1990).