Read about the history of naval defences and mining strategies in New Zealand. Learn about North Head, Fort Takapuna, Spa Torpedo Boats and German and Japanese submarines operating in New Zealand waters.
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.
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
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.
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.
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.
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.