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Ton Class Hunter

The ships of the Ton class of minesweepers have names were all chosen from villages ending in -ton. The Ton class were coastal minesweepers built in the 1950s for the Royal Navy, but also used by other navies such as the South African Navy and the Royal Australian Navy. They were intended to meet the threat of seabed mines laid in shallow coastal waters, rivers, ports and harbours.

At the end of the Second World War it was generally accepted that the emphasis on explosive antiship mines had shifted from deeply laid moored mines to ground mines laid in the shallow approaches to ports and harbours. The large steel built ocean minesweepers were, therefore, mostly unsuitable for sweeping sophisticated modern mines laid in coastal and inshore waters. As a result, a team was formed at Bath in the UK in 1947 to design a new generation of minesweepers.

This team produced sets of hull drawings in 1949 for the construction of future coastal mine countermeasure vessels, each hull design being further subcategorized into two variants, namely a minesweeper and a minehunter. Although no orders were initially placed, mainly owing to a lack of funding, the impending offensive in Korean waters and the cold war with all communist countries, Russia in particular, led to the acquisition programme being brought forward to September 1950. The coastal minehunter variant was, however, suspended in June 1952 and cancelled altogether in March 1953, because no suitable minehunting sonar had been developed.

The Ton class were coastal minesweepers built in the 1950s for the Royal Navy, but also used by other navies such as the South African Navy and the Royal Australian Navy. It was originally planned to name the ships after insects, with names like Red Ant, Green Cockchafer and so on, but this plan was abandoned and the Royal Navy ships of the class were given names of British towns and villages ending in "-ton", hence the name of the class.

The Ton Class proved to be a very successful design with 119 units built in British yards between 1951 and 1960. Over thirty units were subsequently transferred to Commonwealth and foreign navies during the ensuing years, and the same basic design was also adopted by many Western navies for their own local construction programmes.

John I. Thornycroft & Co Ltd, of Southampton, acted as parent firm to the group of fifteen smaller shipbuilders responsible for constructing these vessels, which were designed to sweep both moored and ground mines. With the exception of the double mahogany hull planking, almost the entire vessel was constructed from light aluminium alloy and phosphor bronze with the lowest possible magnetic field to achieve optimum safety when sweeping for magnetic mines. An eddy current compensator and internal degaussing coils adjusted the magnetic signature of the ship to zero when it rolled at sea. They were protected from pressure mines by their low displacement, and the threat of moored mines was greatly reduced by their shallow draught. To prevent potential damage caused by marine parasites, they were also fitted with a protective Cascover nylon sheathing on the outer shell below the waterline.

They were intended to meet the threat of seabed mines laid in shallow coastal waters, rivers, ports and harbours, a task for which the existing ocean-going minesweepers of the Algerine class were not suited. The design of the class was led by the shipyard John I. Thornycroft & Company, and drew on lessons learnt in the Korean War, and numbered 119 vessels. They were diesel powered vessels of 440 tons displacement fully laden, constructed of wood and other non-ferromagnetic materials. Their small displacement and shallow draft gave them some protection against pressure and contact mines, and allowed them to navigate in shallow inshore waters. Primary armament was one Bofors 40 mm gun, although the South African variants also had an Oerlikon 20 mm cannon behind the funnel and a M2 Browning machine gun mounted midships. Sweeping equipment was provided for moored mines and magnetic mines. Thornycroft & Co of Southampton was the lead shipyard for the class.

Early vessels had Merlees diesels, then the more powerful Napier Deltic (photo) was fitted and eventually the original Tons were re-engined with Napier Deltics, an engine with wide spread usage including railway locomotives. Early members of the class had an open bridge and the lead-ship, Coniston had no top to her funnel and a short lattice mast. Subsequent vessels had a double-finned funnel top and covered bridges were progressively introduced. The last major external change was to revert to a tripod mast to carry new radar.

In 1964 Kirkliston was converted to a minehunter, with LL sweep gear removed and minehunting Type 193 sonar installed, with the top of the dome in the aft seamans mess and the console in the ops room aft of the wheelhouse. Active rudders were fitted to allow her to position herself precisely, and four divers and two inflatable boats were carried to permit detected mines to be blown up by explosive charges placed by the divers.

Six Tons (4 minesweepers and 2 non converted minehunters) were transferred to the Royal Australian Navy in 1961 with another four to the Indian Navy, one to Ghana, eight to South Africa, six to Argentina in 1968 and three to the Republic of Ireland in 1971.

With the rundown of the Royal Navy fleet in the 1960s, many were sent to become base ships for the Royal Naval Reserve allowing reserve crews to get to sea for short periods without a lot of effort to organise a crew of significant size. Some of these had their names changed to reflect the RNR Division they were attached to. The RNR vessels lasted until the introduction of the River class minesweepers in 1984. The remainder of the RN ships paid off in the 1990s.

By 1984 the 'Tons' were the oldest operational warships in the Royal Navy: at least two had passed their 30th birthday. They have been refitted, rebuilt, modernised and modified to take each new item of equipment as it became available - at a price. There were those who believed that the Royal Navy has sacrificed its ships on the altar of habitability. The 'Ton' Class Minehunter (MHC) provided an object lesson in what sailors will accept when they believe in their equipment. One only had to look at a lower messdeck, occupied largely by sonar operators, who suffered many sleepless nights while the maintainers wrestle with the eccentricities of a leaking sonar directing gear which now takes up all of the space which was once provided for recreation.

Length 152ft.
Beam 28ft.
Draught 8ft.
Range 2300nm. @ 13 knots
Engines 2 x Napier Deltic 'Y' diesel engines @ 3000hp. Generator Foden powered by 1 x Napier Deltic.
Speed cruise @ 13 knots on one engine. maximum 16 knots on both.
Rudders Normal variable until 1968 then active. Ships company 5 + 28
Armament 2 x 40/70 bofors until 1968 then 1 x 40/70.
Boats 16ft. slow motorboat until 1968. Assault boat in Malaysia. After 1968 2 x inflatables.
Radar 975 (still working in 2005).
Sonar after 1968 A/S 193

Page last modified: 18-08-2016 15:46:47 Zulu