Steel Sloops in the RN

Like the larger Frigate the Sloop did not initially survive the transition to steel and steam. At the turn of the 19th century the RN had a few sail and screw powered sloops such as the Condor Class, armed with 4 x 4" guns and the Cadmus with 6 x 4" guns. The last were built in 1901, most survived until WW1 where they were pressed into the roles of minesweepers and coastal escorts.

In 1915 a new building program began of armed Minesweepers which would operate in defence of the Main Fleet. Classed as Sloops and designated the Flower Class these remained in construction throughout WW1, though by 1917 their primary role had changed from Minesweeper to Convoy Escort as the war at sea switched from a Fleet confrontation to Merchant Blockade in the Atlantic and North Sea.

Acacia Class

The WW1 Flower Class were split into a number of Sub-Classes, the first was the Acacia Class.

Purpose built as Minesweepers 24 were built, they had reinforced bows to improve survivability if struck by a mine. They were armed with 2 x 12 Pdr and 2 x 3 Pdr guns to defend against Destroyer attacks and displaced 1200 tons, could do 16 Knots and had a crew of 90. Length overall 262 ft, Draught 12 ft, beam 33 ft. They had a range of about 2,000 miles. Coal powered carrying up to 250 tons they were powered by a 4 cyl reciprocating engine with triple expansion and 2 cylindrical boilers driving a single screw.

In 1917 they were re-fitted to carry depth charges and re-deployed as Convoy Escorts.

The Acacia were built as a kind of "Economic Destroyers", fitted with conventional steam engines instead of turbines they were greatly restricted in speed but were not meant to maintain Fleet speeds, rather to clear a path ahead of an intended course.

Although they were to become the premier Escort Ship of the WW1 and went on to become the template for future Escorts they were never designed for the role, they just happened to be available.

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HMS Primrose, a Flower (Acacia) Class Fleet Minesweeper

HMS Jonquil, the two funnels show the double boiler arrangement, but the ship had only a single screw. Reciprocating rather than turbine engines meant they had half the speed of a contamporary Destroyer of the day. This photo was taken in 1951 and shows Jonquil as Carvalho Araujo in the Portugese Navy, fitted out as a Survey Vessel. The WW1 Flowers had a reputation for good sea keeping which was not passed on to their WWII namesakes.

HMS Bluebell, seen on the right. Good sea keeping and long range proved to be better features for a Convoy Escort than high speed and heavy armament. After the Battle of Jutland it became apparent there was unlikely to be another major Fleet action and the Minesweepers were reluctantly released for Convoy Escort duties.

HMS Laburnum, survived WW1 only to be sunk (or perhaps scuttled by crew) by the Japanese at Singapore in 1942 where she was serving as a Headquarters and Drill Ship.

Azalea Class

The Azalea Class were almost identical to the Acacia, displacing a slightly greater 1250 tons with 267 ft overall, beam of 33. ft. But they carried the heavier 4.7" guns, two single mounts, as well as the pair of 3 Pdr guns. 12 were built.

Begonia was converted to a Q Ship and sailed as Dolcis and Jessop as Q10, she was sunk in action with U151, rammed or collided. Mrytle was lost in operations against the Bolsheviks post WW1.

Peony was converted to a Seaplane tender in 1917 and sold between the wars to Greece where she was captured by the Germans and fell victim to a mine and sank September 1943.

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HMS Azalea in Malta after hitting a mine. The bows of the Flower Class Sloop were triple skinned to improve the chances of surviving such a hit, as Azalea did here.
HMS Peony, pictured here post war as the ferry Ardena. Many Flowers went on to Merchant life, testimony to their robust design and good sea keeping qualities.

Azalea

Sep 1915 - Feb 1923

Arabis Class

The Arabis sub class represented the largest building program of Sloops, 36 were built. The specifications are the same as for the Azalea Class at 1250 tons, 267 ft overall, beam of 33.5 ft. Main weapons were supposed to be 4.7" but some were fitted with 4".

Aubretia Class

Q Ships were warships designed as merchantmen, their tactic was to lure a U-Boat to the surface and then engage with guns. It is not clear if all the Class were actually employed as Q ships, where I have established that they were I have given their Q Numbers.

The Aubretia and the following Anchusa Class were extraordinary ships. Using the Flower hull and machinery commercial ship yards were given orders to construct ships along their own standard patterns upon the hull. Hence there is no standard to the designs, weapons were hidden in a variety of ways including mounting on reversing hatches, screened by drop shields and false deck houses.

Secrecy about the ships was very tight and there is little information to be had even to this day. They were however the first ships to be purpose built as Convoy Escorts and were classed as Convoy Sloops.

Displacement 1250 tons, 267 ft overall, 33.5 ft beam, 11-12 ft draught.

Armament varied but nominally 3 x 12 Pdr, 2 x 3 Pdr, in service generally 2 x 4" guns, a 3 Pdr and Depth Charge throwers.

Q-Ships were a violation of International Law but were considered justified due to U-Boat operating out of the law also. The tactic was an old one often used by the RN to lure enemy ships close to an armed merchantman, it was a matter of pride and old law that a ship showed it's real flag before opening fire. The phrase has passed into general use: Showing your true Colours.

In 1915 the Baralong incident laid Britain open to war crime charges when the HMS Baralong shot U-Boat survivors in the water, the Captain claimed he believed they were attempting to swim to another merchantman with the intent of capturing it! Six U-Boat survivors who made it to the Nicosian were killed by a boarding party from the Baralong.

Anchusa Class

Like the Aubretia Class the Anchusa were purpose built Escort Sloops, deliberately designed to resemble merchantmen, and many with hidden weapons. Unlike the original Flowers they were never equipped with mine sweeping gear but were designed to carry depth charges including four throwers. Other than that they varied little from the original design, the ship's had already proved they were up to the task.

The large building program of 28 ships was in response to the resumption of unrestricted submarine warfare and the final recognition of the need for convoys and suitable escorts.

They were slightly larger at 1290 tons, length 262 ft overall, 35 ft beam with up to 13.5 ft draught. Armament varied, they were designed for 2 x 12 Pdr, 1 x 7.5" Howitzer and 4 throwers, but usually only carried 2 x 4" and various lighter weapons.

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HMS Harebell, due to their secret methods of operation there is little recorded about these ships. Harebell shows only a single funnel, multiple funnels were usualy a good indication of a warship, except liners. Oddly though Harebell's weapons are not hidden at all here.

HMS Saxifrage, still survives as the former HMS President, now a conference centre moored on the banks of the Thames.

HMS Gilia, taken just after the war she is openly showing the White Ensign, but this shot shows how well the weapons were hidden.

24 Class

The so called "24" Class were the last Sloops to be built in WW1, a total of 22 were completed, but only 10 before the end of the war. All were named after famous Racehorses and are sometimes referred to as the Racehorse Class, although Jane’s of 1919 is clear they are known as the Type 24, Jane’s also notes they were never intended as Q Ships & that they were poor sea keepers, most were sold or scrapped in 1920.

They are something of an oddity as they regressed back to Fleet Minesweepers, they have the appearance of a merchantman and are also oddly symmetric with a single mast and an aft deckhouse to match the Bridge, this together with dazzle paint was reckoned to confuse a U-Boat attempting to get a torpedo firing solution. Personally I think they were intended to be Escorts but with the end of the war nigh the powers were keen to return to old standards and re-classified them as Fleet Minesweepers.

1320 tons, 267 ft length overall, beam 34'10" and 12 ft Draught, weapons were 2 x 4" and wartime versions one or more 3 Pdr. The overall similarity to the Flower is lost when the hull design is compared, it appears that sea keeping was lost in favour of an attempt to fool torpedo aiming.

The re-classification to Minesweeper is a rather sad indication of thinking at the end of WW1, the strange belief that the U-Boat genie could somehow be returned to the bottle and things would go back to the way they were. This astonishing attitude would prevail until even the blindest had to see the Nazi U-Boats rolling off the slipways.

Bridgewater Class

The Bridgewater owed a lot to the Flower Class Sloop, of similar size, design and armament, but upgraded to turbine power with twin screws, though oddly with no speed advantage. They were, against all logic, also back to being Fleet Minesweepers which could also act as gunboats on foreign stations, the U-Boat bogeyman was no longer a problem it seems.

Displacement 1045 tons, beam 34 ft, Length 264 ft and draught 11.5 ft they were almost identical to the Flower and had the only marginally better speed of 17 knots. Armed with two 4" guns, one high angle. The only nod to sanity was they were fitted for depth charges, but not with. Complement was 100 in peace time.

Originally it had been intended to fit one of the two ships with turbine and the other with diesels to conduct comparison trials, but in the event no suitable diesels were available. Main design changes to the Flower is the foremast moved behind the Bridge, the raised forecastle extended two thirds of the hull from the bow, a heavy weather advantage that would have to be re-learned the hard way in other classes. Although of no speed advantage the twin screws provide hugely better manoeuvrability, crucially in tight turns which was the key to defeating a U-Boat which themselves relied on manoeuvrability to avoid destruction on the surface.

Hastings Class

A number of classes followed the basic design of the Bridgewater, the first was the Hastings Class.

A fifth Hastings Class, the Hindustan was built for the Royal Indian Navy and the flash point for the Indian Mutiny of Feb 1946.

266 ft overall, Beam 34 ft 1", 17 Knots, draught 12 ft 6 in, armament accounts vary but was probably a standard 4" and a high angle 4" like the Bridgewater. Scarborough was disarmed prior to the war and later rearmed with a 4" high angle, a 12 Pdr and 15 depth charges, later increased to 80.

Shoreham Class

8 ships were built between 1930 to 1932. Many accounts state the Shoreham and the Hastings also carried a 4.5" gun, but this is not bourne out in accounts and photographs and is more likely a confusion from 4 x 0.5" machine guns.

Armament was increased during the war, Shoreham for instance received a two quad 0.5" machine guns, three 20 mm and a 2 Pdr pom-pom. Built as Minesweepers with an auxiliary role as Anti-Submarine.

Length 250 ft at the waterline, probably 267 ft overall, identical to the previous classes, speed of 17 knots.

Displacement 1105 tons, armament 2 x 4" guns, quad .5" machine guns.

Grimsby Class

Accounts vary on the Classification of these interwar Sloops, in truth there is so little difference between them that the only distinction between classes is probably the Batch in which they were ordered.

The Grimsby though were broader in the beam and more heavily armed. 8 were built for the RN, 1 for the RIN and 4 for the RAN. The RAN ships were actually built on the previous hull with the narrower beam and the Indian ship was 30 ft longer and with a intermediate beam of 35 ft 6" making them rather doubtful inclusions in this class.

The RAN ships were equipped as Escort Destroyers with 3 x 4", 4 x 3 Pdr, machine guns, depth charges and 2 twin 21" torpedo tubes.

The RN ships however were still completed as Minesweepers, but range had been increased to an impressive 5,700 NM. Length 250 ft waterline, 266 ft overall, beam 36 ft, displacement 1,300 tons. Armament 2 x 4.7" guns with a 3" superimposed on the forward gun and a quad 0.5" machine gun.

Bittern Class

The Bittern Class are proof positive that sanity was not to be had between the wars when it came to escort ships. HMS Bittern was to be a true escort vessel, gone was the mine sweeping gear, she was dedicated with depth charges and 3 x 4.7" guns, 4 x 3 Pdr and a quad 0.5" machine gun. The hull remained the same at 266 ft overall and with the broad beam of the Grimsby at 36 ft, displacement was 1650 tons and improved engines gave a higher speed of 18-19 knots. She was a well armed ship, though lacking in light AA as were all ships pre-war.

But Bittern was completed as Enchantress, an Admiral's yacht, the aft turret was replaced with a deckhouse accommodation and even after war was declared the turret was not replaced (probably because the complex turret mount and shaft had never been fitted).

HMS Stork fared even worse, she was completed as a Survey Ship with no weapons at all, just the ticket on the eve of war. After the outbreak of was she was refitted with high angle 4" guns in three twin mounts, losing valuable months of Operational life.

The third ship was named HMS Bittern (presumably the Admiral did not like the name for his own ship) and completed as designed with 3 x 4.7" guns, but she was lost to air attacks off Norway, highlighting along with many other disasters the chronic need for better AA fit.

HMS Bittern, stricken by dive bomber attacks off Norway. Lack of adequate AA weaponry would cost the RN dearly in the early months of the Second World War.

Egret Class

In the Egret Class the well proved hull of the Seaside Town Sloops was used as a basis, but extended to 292.5 ft and widened again to 37.5 ft. Displacement was 1250 tons, 1640 fully loaded. Speed was 19 knots and peacetime compliment was 188, war time is not known but records show that 194 crew were killed on Egret when she was sunk by a Glider Bomb.

Recognition of the air threat was clear, she was armed with 8 x 4" High Angle guns in 4 turrets, but again there was a failure to provide close in weapons, a single quad 0.5" machine gun was mounted. Two of the Class would be lost to air attacks.

Auckland was laid down as Heron, but then changed to Auckland and was to have been completed as an unarmed Survey Vessel for the New Zealand Station. But with the worsening political situation she was armed as originally designed. Accounts note that her forward guns continued firing even after she was sinking astern. Survivors abandoned ship just before she blew up and were machine gunned in the water by German aircraft.

Not surprisingly ships of this type are often referred to as Destroyers, apart from a lower speed and the lack of torpedoes there is little to distinguish them. Other Navies adopted the Class DE or Destroyer Escort, but the RN only flirted with the idea in the Hunt Class. No other country had to defend such extended lines of maritime communications and the principle of the destroyer was always speed and more speed, a long range convoy escort needed endurance in heavy weather and range, which suited a broader beamed ship than a destroyer.

Black Swan Class

Also known as the Modified Egret Class, this is the best known of the larger escorts, they were constructed throughout the war and were premier hunter killers, ironically considered too good to tie down to a convoy they were often employed in Support Groups which would go to the aid of an attacked convoy, or track submarines as they deployed or returned to base.

Their impressive armament also meant they were sometimes used for other duties such as shore bombardment.

The hull was again the same tried and trusted design, but increased again to a length of 283 ft and a beam of 38 ft. With a speed of 19 knots hey were capable of catching any of the conventional U-Boats and had the endurance for long range convoy work giving 7,500 NM at 12 knots cruising.

Armed with 6 x 4" guns as opposed to 8 on the Egret this gave the Class a much greater Depth Charge capacity and improved sea keeping and allowed for additional equipment to be fitted later in the war. Displacement was 1600 and 1250 unladen. Apart from the 4" guns they carried 4 x 2 Pdr pom-pom and a quad 0.5" machine gun. Later the AA fit was changed to 12 x 20mm Oerlikons in 6 twin mounts.

It is often quoted that the Black Swan Class could not be adapted to forward firing ASW systems such as the Squid, but this is nonsense, the Black Swans could have done so, but only at the expense of one of the forward turrets, given the heavy losses to aircraft the Black Swans retained their guns, particularly as one of their main areas of operation was the Bay of Biscay, hunting U-Boats heading too and returning from patrol.

Modified Black Swan Class

Displacement increased throughout the class construction up to 1950 tons full load, the modifications mainly concerned the increase in AA weapons, but as ships were retro-fitted there was little to distinguish them apart. The Hunter Killer Groups, or Support Groups, often operated within range of German Aircraft and surface units making the unusually heavy gun armament for an Escort Ship invaluable. Early losses during the war showed the need for increased short range AA but it was not until the Korean War that the Class received the 40mm weapons that proved most effective.

Post war the Sloops were employed back in their pre-war role as gunboats of the Empire, such as what remained. In 1947 they were re-classified as Frigates, though this role did not really fit them as the Admiralty were unwilling to allow them to be modified to carry greater anti submarine weapons at the expense of their gun armament. They operated in the troubled Chinese theatre, notably the infamous Yangtze Incident, and in the Korean War, but not as Escort Vessels.

By the war's end their limited speed meant they were already being outclassed by the later model U-Boats and they were too slow to operate as Fleet Escorts as they could not keep up with the Carriers. They declined as the Empire did as foreign stations where they were much needed and appreciated slowly fell away.

It says much for the class that construction continued on some of the ships even after the end of the war when most ships were being cancelled even before the war's end.

Tribal Class Sloop

By the mid 50's the WWII Bird Sloops were at the end of their life, hard service in two wars meant they were suffering increasing breakdowns, and their speed even as Patrol Boats was becoming too slow as smugglers and insurgents used high speed boats to evade them. There was a need for a replacement that could cruise long distance at low speed, but sprint at need, and which could mount the latest in weapon and sensor systems. The increasing use of aircraft by hostile groups also required the ability to track air traffic and direct interceptors at need.

The result was one of the most extraordinary and innovative ship designs ever, a true maid of all work, the Type 81 Tribal Class Sloop. Intended from design as a colonial patrol boat she could attack submarines, shore targets, small vessels and give a good account of herself in air defence. She carried long range air radar, and even deployed a lightweight helicopter which could itself deliver anti surface or anti submarine weapons, and extend the patrolling ability of the ship.

Yet it was a design of incongruities, she carried a revolutionary guided missile anti aircraft system, but mounted open turret early WWII guns salvaged from scrapped destroyers. She had a state of the art gas turbine for high speed, but still used steam for low speed where diesels were far superior..

Displacing 2700 tons overall (2300 tons unladen) the Tribals were 360ft long and 42 ft 4" in the beam, considerably larger than the Black Swans, they also carried a disproportionaly higher crew complement of 253 in peacetime. Draught was 13 ft 3". Max steam speed was 20 knots and combined Steam and Gas (COSAG) was 28 knots, range 5,300 miles at 12 knots. A significant improvement over other ships was that steam ships took four hours to get to sea from cold, using her Gas turbine a Type 81 could be at sea in minutes.

Original weapon fit was 2 x 4.5" guns in single mounts (removed from C Class Destroyers), 2 x 40mm Bofors and the Limbo ASW Mortar. The Bofors were an interim measure while the Seacat AA missile was being developed. She was equipped with the Wasp light helicopter armed with depth charges, Mk 44 homing ASW torpedoes and AS11 air to surface missiles. Later modifications included retro fitting two 20mm Oerlikons to deal with small coastal craft, these were referred to as "Junk Bashers."

There were problems with the design, the twin funnels restricted upper deck space, the use of the hanger roof as a flight deck meant that in any kind of sea the motion of the ship was exaggerated making flying operations difficult. But many of the features of the ship were to be adopted into the Type 12M, the Leander, in particular the helicopter, long range air warning radar, single Limbo, and less obviously: bunk accomodation and centralised messing.

In common with other small ship designs of the time the ships were designed to be constructed in pre-fabricated sections and could be assembled in un-speciallised yards. The ships remained pretty much as built with the exception of the retro-fitting of Seacat, and two ships received 199VDS sonars, Corvus 3" rocket decoy launchers were also fitted, replacing launcher cradles on the forward gun.

Radar: 965 long range air warning, 978 Navigation, 262 Seacat Blind Fire Director, 903 Gun Director, 292 medium range (upgraded to 993 later)

Sonar: 162 bottom search, 170 Limbo mortar attack, 177 Search, 199 VDS on Ashanti and Gurkha

The ships went into the reserve fleet in 1980, scheduled for disposal, but with losses in the Falklands Tartar, Ghurka and Zulu were recommisioned using parts robbed from the remaining ships. All three were later bought by Indonesia. Plans to upgrade the class to a single funnel, an automatic gun and Lynx helicopter were proposed by Vosper Thornycroft but rejected.

Although designed and built as Sloops and initially at least used in traditional peacetime Sloop roles of peacekeeping the class were designated Frigates on commission for political reasons, the UK had agreed to provide a minimum Frigate force to NATO and were in danger of falling below that commitment.

For me the the criteria is simple: the Type 81 Tribal was laid down as a Sloop, the Type 21 was always intended to be Frigate, even if only for political reasons, a stopgap while the Type 22 was quarelled over and generally messed up in the design and procurement stage. The Type 81 was the last steel Sloop.