The Ham class was a class

Ship class

A ship class is a group of ships of a similar design. This is distinct from a ship-type, which might reflect a similarity of tonnage or intended use. For example, the is a nuclear aircraft carrier of the Nimitz class....

 of inshore minesweeper

Minesweeper (ship)

A minesweeper is a small naval warship designed to counter the threat posed by naval mines. Minesweepers generally detect then neutralize mines in advance of other naval operations.-History:...

s (IMS), known as the Type 1, of the British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

. The class was designed to operate in the shallow water of river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

s and estuaries

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

. It took its name from the fact that all the ship names were British place names ending in -"ham". The parent firm who were responsible for supervising construction was Samuel White

J. Samuel White

J. Samuel White was a British shipbuilding firm based in Cowes, taking its name from John Samuel White . It came to prominence during the Victorian era...

 of Cowes

Cowes

Cowes is an English seaport town and civil parish on the Isle of Wight. Cowes is located on the west bank of the estuary of the River Medina facing the smaller town of East Cowes on the east Bank...

, Isle of Wight.

The class consisted of 93 ships, launched between 1954 and 1959. (M2601) was the first. They were built in three slightly different sub-groups, the first sub-group being distinguished by pennant number

Pennant number

In the modern Royal Navy, and other navies of Europe and the Commonwealth, ships are identified by pennant numbers...

s beginning with 26- and the second and third sub-groups being distinguished by pennant number

Pennant number

In the modern Royal Navy, and other navies of Europe and the Commonwealth, ships are identified by pennant numbers...

s beginning with 27-. The 26- group were of composite construction (wood and non-ferrous metal

Non-ferrous metal

In metallurgy, a non-ferrous metal is a metal that is not ferrous, that is, any metal, including alloys, that does not contain iron in appreciable amounts...

s and the 27- group were all-wooden, of which the third sub-group differed by having a prominent rubbing strake around the hull and slightly enlarged dimensions.

The vessels displaced 164 tons

Long ton

Long ton is the name for the unit called the "ton" in the avoirdupois or Imperial system of measurements, as used in the United Kingdom and several other Commonwealth countries. It has been mostly replaced by the tonne, and in the United States by the short ton...

 fully laden and were armed with one 40 mm Bofors

Bofors 40 mm gun

The Bofors 40 mm gun is an anti-aircraft autocannon designed by the Swedish defence firm of Bofors Defence...

 or 20 mm Oerlikon

Oerlikon 20 mm cannon

The Oerlikon 20 mm cannon is a series of autocannons, based on an original design by Reinhold Becker of Germany, very early in World War I, and widely produced by Oerlikon Contraves and others...

 gun. They were 32.5 metres long overall by 6.4 metres beam. The construction was of wood to minimise magnetic signature. The crew complement was 15, rising to 22 in wartime.

The engines of this class were Paxman

Paxman (engines)

Paxman is a major British brand of diesel engines. Ownership has changed on a number of occasions since the company's formation in 1865, and now the brand is owned by MAN SE, as part of MAN Diesel & Turbo. At its peak, the Paxman works covered 23 acres and employed over 2,000 people. Engine...

 diesels

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

, some of which were built under licence by Ruston and Hornsby

Ruston (engine builder)

Ruston & Hornsby, later known as Ruston, was an industrial equipment manufacturer in Lincoln, England, the company's history going back to 1840. The company is best known as a manufacturer of narrow and standard gauge diesel locomotives and also of steam shovels. Other products included cars, steam...

 of Lincoln

Lincoln, Lincolnshire

Lincoln is a cathedral city and county town of Lincolnshire, England.The non-metropolitan district of Lincoln has a population of 85,595; the 2001 census gave the entire area of Lincoln a population of 120,779....

. Each vessel had: two 12YHAXM (intercooled) for main propulsion, rated 550 bhp at 1,000 rpm, plus one 12YHAZ for pulse generation. Maximum speed was 14 knots (27.4 km/h) dropping to 9 knots (17.6 km/h) when mine sweeping.

The class shared the same basic hull as their minehunting

Minehunter

Minehunters are mine countermeasure vessels that actively detect and destroy individual naval mines. Minesweepers, on the other hand, clear mined areas as a whole, without prior detection of mines...

 counterpart, the Ley-class

Ley class minehunter

The Ley class was a class of inshore minehunter built for the Royal Navy in the mid-1950s. They had pennant numbers in the series M2001. Eleven ships were built in the early 1950s, most of which were subsequently disarmed and used as training vessels, RNXS tenders, URNU vessels etc.Unlike...

 and the Echo-class

Echo class survey ship (1957)

The Echo class was a class of inshore survey vessel built for the British Royal Navy in 1958–1959. The class was designed to operate in close waters such as harbour approaches, shipping lanes, rivers and estuaries...

inshore survey craft.

Ships

(IMS87) (IMS02) (IMS03) (IMS04) (IMS05) (IMS06) (IMS85) (IMS07) (IMS08) (IMS09) (IMS10) (IMS11) (IMS12) (IMS13) (IMS14) (IMS15) (IMS16) (IMS17) (IMS18) (IMS19) (IMS31) (IMS21) (IMS22) (IMS23) (IMS24) (IMS25) (IMS26) (IMS27) (IMS28) (IMS29) (IMS30)
(IMS54) (IMS20) (IMS32) (IMS88) (IMS33) (IMS34) (IMS35) (IMS36) (IMS37) (IMS42) (IMS39) (IMS01) (IMS40) (IMS41) (IMS38) (IMS43) (IMS44) (IMS45) (IMS89) (IMS46) (IMS47) (IMS48) (IMS49) (IMS50) (IMS51) (IMS83) (IMS52) (IMS53) (IMS55) (IMS56) (IMS92)
(IMS82) (IMS81) (IMS57) (later HMS Waterwitch) (IMS58) (IMS84) (IMS59) (IMS86) (IMS60) (IMS61) (IMS62) (IMS91) (IMS64) (IMS63) (IMS65) (IMS66) (IMS68) (IMS67) (IMS69) (IMS70) (IMS90) (IMS71) (IMS72) (IMS73) (IMS74) (IMS75) (IMS76) (IMS77) (IMS78) (IMS79) (IMS80) (later HMS Woodlark)