J Class Destroyers

Feature Article
Written by
James Davies

Key Information

Introduction

Destroyers are small warships (defined in the London Treaty of 1930 as being no more than 1,850 tons), and armed with light weapons (guns of calibre no more than 5.1 inches (130 mm)). In the British Royal Navy during the second world war a ship must also be fitted with torpedo tubes to be classed as a destroyer. They are usually equipped for anti-submarine work, although some may alternatively be equipped for minelaying operations.

Before the second world war new British destroyers were generally designated as fleet destroyers, for work in support of the main fleet, which includes cruisers and capital ships. Experience during the war lead to older destroyers often being refitted and re-designated as escort destroyers (principally because older destroyers lacked the speed of modern warships) and used for less glamorous tasks such as convoy escort. The need for new specialist escort destroyers was recognised, however, and these were also built during the war. The J class ships are fleet destroyers, equipped for anti-submarine work.

Eight ships formed the J class (HMS Jervis as the flotilla leader, with the others being HMS Jersey, HMS Jaguar, HMS Juno, HMS Jupiter, HMS Janus, HMS Jackal and HMS Javelin). They mainly served in the Mediterranean, and were fitted with improved anti-aircraft armament compared to all previous British destroyers. Nevertheless, (as with all small ships) they were extremely vulnerable to air attack and later fleet destroyers tended to have anti-aircraft armament that was better still. Only two ships survived the war, with five being sunk before the end of 1942.

Despite the heavy losses of J class it was generally accepted that the design was sound, and formed the basis for the ‘emergency’ designs that followed. A total of 124 ships entered service as variations on the J class design, although 28 of these were completed after the end of hostilities.
 

Development

The naval treaties between the wars had a significant effect on the design of all warships. Weight limitations forced all naval powers to focus on weight saving designs, bringing significant advances in several areas, such as advanced propulsion systems and dual purpose weaponry (to be used in both surface and air actions). The previous destroyer class - the Tribal class - were very much larger than all other existing British destroyers, with a correspondingly greater cost to build. The J class was intended to be a compromise, smaller and cheaper than the Tribal class and yet with comparable speed and armament.

The J class were fitted with a total of six main guns and 10 torpedo tubes, compared to the Tribal class with eight main guns and four torpedo tubes. This increase in torpedo tubes represented a significant improvement in the capabilities of the ship over the Tribal class, giving them a bigger punch against capital ships. The reduction in main guns from eight to six was in practice not significant, and as most British destroyers were only armed with four guns the J class were considered to be heavily armed.

There had long been a desire to produce dual purpose guns for destroyers which could be used both against aircraft and against surface targets. The Admiralty was having considerable trouble developing a high-angle gun mounting, and eventually it was decided to retain the low angle mount, which was limited to a maximum of 40 degrees elevation. As with the Tribal class, each mount was fitted with twin 4.7 inch (119 mm) guns. After considerable debate within the Admiralty the aft gun was designed to train in a forward position, which resulted in a blind spot over the stern of about 20 degrees whilst providing for easier engagement of targets ahead. This decision reflected the traditional favour of offensive action over defensive measures. These guns were capable of firing 10 rounds per minute each, with the rounds weighing 50 pounds (22.8 kg).

For air defence a four barrelled pom-pom was fitted. This at last gave British destroyers some defence against dive-bombers, as they fired 115 rounds per minute per barrel, and were effective out to 1100 metres (1203 yards). Finally, eight 0.5 inch (13 mm) machineguns were installed in two mounts of four guns each, although these were found to be prone to jamming.

For the anti-submarine role the ships were fitted with asdic and depth charges. Asdic was a standard feature of British destroyers at this time. It was effective out to about 2500 yards (2286 metres), although high speed and bad weather both adversely affected its operation. Generally asdic was ineffective if the ship was travelling above about 18 knots, and was unable to detect anything within about 200 yards (183 metres) of the ship. Two racks of depth charges were provided at the stern of the ships, as well as two depth charge throwers on either side. Depth charges had to explode within about 20 feet (6.1 metres) of a submarine to breach its hull, and in the initial stages of the war the British depth charges' maximum setting was over 100 feet (30 metres) shallower than the maximum depth that a U-boat could dive to.

To protect the fleet from mines provision for a two speed destroyer sweep (TSDS) was fitted to all but HMS Jervis, who as the flotilla leader had increased accommodation for staff which reduced the space available at the stern of the vessel.

The J class was the first to have only a single funnel, with improvements in boiler design allowing the ships to be fitted with two more powerful boilers rather than the three fitted to the previous Tribal class destroyers, with the net power output being similar.

Longitudinal framing was chosen for the J class which, when combined with electric arc welding, allowed the ship to be built more easily. Transverse frames were still required around the machinery spaces however, to provide the required structural support.

The profile of a J-Class destroyer is shown in below. The framing detail is an indication only, and is not meant to represent actual framing.

A destroyer's primary assets were speed and manoeuvrability. As with most destroyers, no attempt was made to provide armour. This was because the amount required to protect the ship from enemy weapons causes a significant increase in ship size, power requirements and cost.

There was some discontent when it was found that the J class were only slightly smaller than the Tribal class (356.5 feet compared to 377 feet for the Tribals), had fewer main guns (six compared to eight), and yet cost more to build (£390,000 each compared to £340,000). Their performance silenced the critics, and the basic hull form was used in many future variants.

The Royal Navy originally intended for destroyers to operate in groups of nine, with eight ships under the control of one Captain (Destroyers), normally known as Captain (D), in a ninth (larger) vessel. This arrangement was found to be difficult to control in exercises just before the war, and tactical units of four destroyers were seen to be more flexible. It was thus decided to build eight J class ships, with the ninth (HMS Jubilant) being cancelled before building began. This also reduced the cost and simplified the creation of destroyer fleets as considerable effort was needed to create the single special larger vessel for Captain (D) and his staff.

Modifications to the ships were made during the war, following the general trend of improving anti aircraft armament and providing radar capability. These are listed in the 'Major Modifications' chapter.
 

J-Class Fleet Destroyer Profile

Variants

There is a tradition in shipbuilding of finding a design that works, then modifying it for other newer ships so that the best of the old can be combined with new knowledge. Evolution rather than revolution is the watchword. The reasons for this are complex, but given the unpredictable nature of the sea, the time and cost of construction, the difficulty of predicting performance for a new design (still a problem today), the need for more destroyers quickly, the inability to build a prototype for testing, the difficulty of future modifications and the potential consequences of failure it can perhaps be understood why many subsequent fleet destroyers adopted a slightly simplified version of the J class hull form.

Although the variants listed below were all different in detail from the J class, with later models incorporating hard-won war experience, they were essentially J class ships. They all had the same power plant and basic hull form, the same speed and similar main weapons (generally with slightly reduced guns to speed construction and reduce cost). Often anti-submarine capability was increased, along with anti-aircraft armament, and the greater weight made them sit lower in the water (with increased displacement and reduced freeboard).
 

K Class

The next class to be built after the J class, the K class, were repeats of the J class, except that TSDS was not fitted. There were eight vessels (HMS Kelly as the flotilla leader, with HMS Kandahar, HMS Kashmir, HMS Kelvin, HMS Khartoum, HMS Kimberly, HMS Kingston and HMS Kipling).
 

N Class

After experimenting with larger destroyers it was decided to revert to the basic J class design. The resulting N class incorporated the modifications already in the J class ships, with a four inch anti aircraft gun replacing the aft torpedo tubes, two additional 20 mm anti aircraft guns and two twin 0.5 inch machineguns. In all apart from HMAS Norman 20 mm guns were fitted in place of the quadruple 0.5 inch machineguns (HMAS Norman was modified later). They were all built with both air warning and air ranging radar. Eight ships were built, with the Royal Australian Navy receiving HMAS Napier, HMAS Nestor, HMAS Nizam and HMAS Norman, the Royal Netherlands Navy receiving the Noble and the Nonpareil (renamed the Van Galen and the Tjerk Hiddes), the Polish navy receiving the Nerissa (renamed as Piorun) and only HMS Nepal was retained by the Royal Navy.
 

Q Class

The Q class combined the armament of the O class with the hull of the J class. They had four 4.7 inch guns, two depth charge mortars, three depth charge racks, one four barrelled pom-pom, six single barrelled 20 mm anti aircraft guns, two 0.303 inch machine guns, and two banks of four 21 inch torpedo tubes. Both air ranging and air warning radar was fitted as standard, as well as asdic. As fewer guns than the standard J class were mounted these ships had increased bunkers at the expense of main gun ammunition, considerably improving endurance. There were eight Q class ships, all of which were manned by the Royal Australian Navy (HMAS Quilliam as flotilla leader, with HMAS Queenborough, HMAS Quadrant, HMAS Quail, HMAS Quality, HMAS Quentin, HMAS Quiberon and HMAS Quickmatch).
 

New R Class

Even though an old R class destroyer of world war one vintage was still sailing (HMS Skate, completed in 1917), the next class were also called the R class. These were essentially repeats of the Q class, although they were fitted with an extra two depth charge mortars (making four in total) and one less depth charge rack (two in total). There were eight vessels in the new R class (HMS Rotherham as flotilla leader, with HMS Racehorse, HMS Raider, HMS Rapid, HMS Redoubt, HMS Relentless, HMS Rocket and HMS Roebuck) all serving with the Royal Navy.
 

New S Class

Again, although old S class ships were still in service with the Royal Navy (a total of 11 vessels, some having seen service in World War One) a flotilla of eight new S class vessels was ordered. These ships were able to incorporate war experience in to their design from the start, and had much improved air defence capabilities. Their four 4.7 inch (four 4.5 inch guns in HMS Savage, fitted to allow sea trials of the new weapon) main guns were dual purpose high and low angle guns, and they also carried a twin 40 mm anti aircraft gun fitted with its own air ranging radar and four twin 20 mm anti aircraft guns. In addition they had two banks of four torpedo tubes, four depth charge mortars and two depth charge racks. Electronic sensors were provided, with asdic, HF/DF, surface warning, air warning and air ranging radar. Two of the ships served with the Royal Norwegian Navy (the Shark and Success being renamed the Svenner and Stord), with the others (HMS Saumarez as flotilla leader, with HMS Savage, HMS Scourge, HMS Scorpion, HMS Serapis and HMS Swift) serving with the Royal Navy.
 

T Class

The T class were repeats of the S class, with minor modifications. One ship (HMS Terpsichore) fitted two additional twin 20 mm anti aircraft guns instead of the twin 40 mm anti aircraft gun. There were eight T class ships (HMS Troubridge as flotilla leader, with HMS Teazer, HMS Tenacious, HMS Termagent, HMS Terpsichore, HMS Tumult, HMS Tuscan and HMS Tyrian), and all served with the Royal Navy.
 

U Class

Again, the U class was a repeat of the S class with a few exceptions. Due to shortages, HMS Ulysses was fitted with a four barrelled pom-pom and HMS Urchin had two additional twin 20 mm anti aircraft guns, both fitted in place of the twin 40 mm anti aircraft gun. The eight U class ships all served with the Royal Navy (HMS Grenville as flotilla leader, with HMS Ulster, HMS Ulysses, HMS Undaunted, HMS Undine, HMS Urania, HMS Urchin and HMS Ursa).
 

New V Class

The V class was another S class repeat, although 23 V class ships from the First World War were still in service at the start of the Second World War (only 17 remained afloat when the new V class were completed). As with the U class, shortages of the twin 40 mm anti aircraft gun meant that HMS Volage had a four barrelled pom-pom in its place. Two of the eight V class ships served with the Royal Canadian Navy (Valentine and Vixen being renamed HMCS Algonquin and HMCS Sioux), and the rest (HMS Hardy and HMS Venus as flotilla leaders, with HMS Verulam, HMS Vigilant, HMS Virago and HMS Volage) served with the Royal Navy.
 

New W Class

Significant numbers of old W class destroyers from world war one were still in service (35 started the Second World War). The new W class were repeats of the S class. The twin 40 mm anti aircraft guns were still in short supply, resulting in HMS Wessex and HMS Whelp having the older pom-pom in its place. All the eight ships served with the Royal Navy (HMS Kempenfelt and HMS Wakeful as flotilla leaders, with HMS Wager, HMS Wessex, HMS Whelp, HMS Whirlwind, HMS Wizard and HMS Wrangler).
 

Z Class

The Z class were modified S class. They had 4.5 inch guns in place of the 4.7 inch guns in the S class, with the guns automatically slaved to the director control tower. To offset the weight of this they mounted slightly reduced anti aircraft armament, with two of the twin 20 mm guns replaced with single 20 mm guns (except in HMS Zambesi, which retained the twin guns). There were eight ships in the class (HMS Myngs and HMS Zephyr being flotilla leaders, with HMS Zealous, HMS Zebra, HMS Zenith, HMS Zephyr, HMS Zest and HMS Zodiac), all of which served with the Royal Navy.
 

CA Class

The CA class were intended as repeats of the Z class. Shortages forced changes in the ships, with HMS Caprice being fitted with a pom-pom in place of the twin 40 mm anti aircraft gun, HMS Caesar having single two pound anti aircraft guns in place of two of the twin 20 mm anti aircraft guns and a single 40 mm gun in place of the twin mount, and HMS Cassandra had single 20 mm guns in place of the twin guns. The eight ships in this flotilla all served with the Royal Navy (HMS Caesar and HMS Cavendish as flotilla leaders, with HMS Caprice, HMS Cassandra, HMS Cambrian, HMS Carron, HMS Carysfort and HMS Cavalier).
 

CH, CO and CR Classes

Three additional classes - CH, CO and CR classes - were similar to the CA class, although improved equipment meant that they had even more severe topweight problems. All had one bank of four torpedo tubes removed, and could carry less depth charges. The delay in supplying the advanced fire control system for these ships meant that none of the 24 ordered were completed before the end of the Second World War.
 

Weapon Class

The final J class variant, the Weapon class, reverted to a modified S class design, although of the 19 ordered in 1943 only four were actually completed as the end of the war came first. These ships were superior to the CH, CO and CR classes, however given the less advanced state of the Weapon class ships it was much more cost-effective to cancel them in preference for the previous variants. Six were cancelled before being laid down, six were laid down but never launched and three were launched but never completed.
 

Operational Use

Fleet destroyers are designed to act in support of a fleet, providing a screen around high value ships. Prior to the outbreak of the war the Admiralty had emphasised the role of the destroyer in the fleet action. British warships thus spent the pre-war years preparing for 'the next Jutland', although this time the enemy was seen to be the Japanese rather than the Germans.

Whilst the fleet was at sea destroyers were expected to prevent submarines getting in range to attack cruisers, capital ships or aircraft carriers. Once battle was joined they were expected to prevent enemy destroyers closing to engage the larger ships with torpedoes, and (if ordered) to themselves close with larger enemy ships and attack them with their torpedoes. The torpedo tubes carried by destroyers made them a considerable threat to capital ships, and their high speed and manoeuvrability made them difficult to hit with the slow-training main guns of capital ships. However, a single hit from a capital ship was liable to put a destroyer out of action.

Destroyers were also used when larger ships could not be risked, and were described by one British Admiral as being 'expendable'. They were often used for scouting waters which were feared to contain mines, submarines or other hazards, or for work very close to shore (which might expose the ships to increased chance of bombardment or air attack).

The J and K classes were heavily involved in action in the Mediterranean (where most of the losses occurred), although they also served against the Japanese later in the war. Only two of the J class survived the war, with much of the losses occurring before the end of 1942. The K class fared little better than the J class, and again only two survived the war. All the K class losses occurred before the end of 1942.

The Mediterranean represented a particularly difficult challenge as an understanding between Britain and France had allocated the Mediterranean to the French. It was expected that France would neutralise any threat there with their fleet (which was equal to the Italian fleet), supported from bases on the south coast of France. With the French capitulation Britain was forced in to allocating scarce resources to respond to the additional threat, leaving the Royal Navy very stretched across the globe. To make matters worse, the situation in North Africa, the loss of Crete and the basing of German aircraft in Sicily deprived British shipping of air cover whilst exposing them to the attention of the Luftwaffe.

In this environment shipping losses were heavy, and destroyers were especially vulnerable with their lack of armour and light air defence. To meet this threat the air defence capability of all ships was improved rapidly and radar was provided as soon as it became available.

The other variants of the J class had a much easier time as by the time they entered service the balance of power had shifted firmly in the direction of the Allies. With the ‘emergency’ shipbuilding programme The British fleet had been considerably expanded, reducing the load on individual vessels and allowing more force to be brought to bear at any one time. Technological improvements (most notably HF/DF and radar) had been fitted as standard, thus removing some of the hazardous scouting work from the destroyer fleet and allowing information to be gathered in a much safer manner. Anti aircraft armament had been upgraded and the Axis no longer had air superiority. Only five of the other variants were lost before the end of the war.

The ships served all over the world, more often in fleet work than in a convoy escort role. Elements served in the Pacific, Atlantic, North Sea, Mediterranean, South China Sea and Indian Ocean.
 

Specifications (As Built)

Note 2: Modifications were made during the war, with the addition of radar and increased anti-aircraft armament in 1940 / 41. Changes were also made after this, generally improving air defence capability and providing better radar.

Note 3: The CH class, CO class, CR class and the Weapon class data are not included as the units were commissioned after the end of hostilities.
 

Major Modifications

Surviving Examples

The Only two J class destroyers survived the war, and no J class destroyers exist today. The last one was scrapped in November 1949. One of the CA class (HMS Cavalier) became a museum ship in 1977.  Many of the variants were sold to other countries (Australia, Canada, Egypt, India, Indonesia, Israel, Netherlands, Norway, Pakistan, Poland, South Africa and Yugoslavia), and the ultimate fate of 11 of the ships is unknown so it is possible that one or more of these has survived.

The one known surviving variant, HMS Cavalier, was significantly modified during her service post-war, including the replacement of one gun with the Seacat missile system, although she is still very similar to the vessel that was built during the second world war. The future of the ship was in doubt for some time as there has been trouble finding sufficient funds to keep the ship, and she was in some danger of being sold. A society has been formed for her preservation and they have managed to secure her survival for the foreseeable future. The society arranged for her to be moved from Tyneside (where she was not open to the public and in a very poor state of repair) to the Chatham Historic Dockyard in Kent, UK. At the time of writing the upper deck only is open to the public, with much work still to do before the internal compartments can be shown.

During a visit in May 2000 there was evidence of much work underway to restore her. Some of the internal spaces could be seen through port holes, and some spaces looked to be nearing full restoration (but not yet open to the public). The deck still retains many of the fittings, such as eyes and ladders, making passage over the deck potentially difficult for elderly or physically handicapped people, although it allows visitors to get a good impression of the difficulties that must have faced the seamen during heavy weather. Of particular interest is the ship's bridge. As with all British destroyers of the time this is open to the elements. Since then much work has been completed, and I understand that many internal spaces are now open to walk through.

HMS Cavalier is the only world war two vintage destroyer in the UK, and can be found at the Chatham historic dockyard. http://www.chdt.org.uk/ (link checked January 2005).
 

Units

British Ships French Ships German Ships Italian Ships Japanese Ships USA Ships Other Ships Documents
Site Map Privacy Policy About The Site News Archive Subscribe To Newsletter