History of Active Mine Countermeasures

Minesweeping is a form of defensive active MCM and can involve mechanical sweeping (towing wires and cutters to sever moored mines from their sinkers or chain sweeps dragged across the seabed) or influence sweeping (using magnetic, acoustic and pressure sources to actuate or jam mine sensors). The following paragraphs relate the history of these two forms of mine countermeasures.

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Minesweeping

In essence, a minesweeper deploys from the stern, cables that cut the anchor cable of the mine bringing it to the surface where it can be detonated by gunfire. Read about minesweeping in New Zealand during World War One and Two.

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Mines Washed Ashore in NZ

Read about mines washed ashore in New Zealand from 1918 to 2008 – where a badly rusted mine was found at Karamea on the West Coast of the South Island.

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Degaussing Ships

Degaussing is a process in which systems of electrical cables are installed around the circumference of ship’s hull, running from bow to stern on both sides. A measured electrical current is passed through these cables to cancel out the ship’s magnetic field. It could be said that degaussing, correctly done, makes a ship “invisible” to the sensors of magnetic mines, but the ship remains visible to the human eye, radar, and underwater listening devices.Read More

Degaussing

The degaussing system is installed aboard a ship to reduce the ship’s effect on the Earth’s magnetic field. In order to accomplish this, the change in the Earth’s field about the ship’s hull is “cancelled” by controlling the electric current flowing through degaussing coils wound in specific locations within the hull. This, in turn, reduces the possibility of detection by these magnetic sensitive ordnance or devices.

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The RNZN Gunnery Branch

Why the Western navies dominated in the 19th century was their pursuit of better gunnery and better guns. Read about the origins of naval gunnery, its development after 1941, and the gunnery branch in the RNZN.

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Firearms in the RNZN

Read about the range of Firearms used in the Navy including the Webley Mk VI revolver and the Lanchester sub machine gun.

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HMNZS Tutira 4-inch gun

The 4-inch gun mounted that was later located near the main gate to HMNZS Philomel on Queens Parade Devonport was originally fitted as the main armament to the Loch-class frigate HMNZS Tutira that served with the RNZN from 1949 to 1961. It was used primarily for surface engagement shore bombardment.

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HMNZS Kaniere Gun

In August 2008 an approach was made to the Museum by the staff of MOTAT in Auckland inquiring if we wished to take back the 4-inch gun mount that was at present at the main entrance to MOTAT.

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HMNZS Achilles Twin 6-inch Turret

This twin Mk. 21 6-inch turret is the ‘Y’ turret from HMS/HMNZS Achilles and was the aft turret when she went into action at the Battle of the River Plate on 13 December 1939.

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Torpedo Bay’s Test Room and Firing of the Mines

Read about the construction of a Test Room in association with the mine station at the Torpedo Bay Yard (the current Navy Museum). Due to the nature of the work required for safety’s sake, the Test Room was casemated into the cliff excavated for the purpose.

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New Zealand Naval Radar in WWII

Read about the introduction of Radar into the New Zealand Division of the Royal Navy, Development of the Training Programme, staff training and Technical and Military Imperatives.

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HMNZS Irirangi – Radio Base

In the heart of the North Island HMNZS Irirangi, the Naval Radio Station was positioned strategically to communicate vital information to Admiralty and the New Zealand fleet. A combined services’ operation, the radio station also drew on the expertise of civilians.

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Cape Brett Lighthouse and Radar Station

The set Cape Brett Lighthouse became operational in early in the Second World War and remained as a RDF station until September 1945. The sets were meant to ‘watch strategic waterways for any unseen movement.

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