USS Implicit MSO-455
Wooden Ship – Iron Men
Mine Sweeping Operations
The Implicit and other aggressive class minesweepers swept mines by entering
the mine field first and towing sweeping gear astern. To reduce the chances of
detonating a magnetic mine the Implicit was constructed of wood, non ferrous
metals and was routinely degaussed to reduce its magnetic signature. Hence
the phrase “wooden ships, iron men.”
Mine sweeping consisted of mechanical sweeps and influence sweeps.
Mechanical sweeps were used to cut the cables of moored mines. Mechanical
sweeps used explosive cutters attached to a sweep wire towed behind the
Implicit. Towed bodies or kites were attached to the wire and were used to
maintain the sweep at the desired depth and to divert the sweep wire out and
away from the side of the ship. A float or para vane was attached to the
end of the sweep wire to keep the equipment from sinking and striking
the sea bottom.
Influence sweeps used towed equipment that emulated a particular ship’s
magnetic and acoustic signature causing the mine to actuate and
explode. Influence sweeps used magnetic generators and acoustic
simulators. Copper mag tails were used to pulse several thousand
amperes through the sea. Kites and para vanes were used with
the magnetic generators and acoustic simulators. Tubular canvas
flotation devices were attached to the mag tails.
Once the equipment was in the water and streamed several hundred
yards out and away from the stern, the minesweeper entered the mine
field. The ship steamed back and forth through the mine field until the
entire field was swept. Maneuvering the ship at the end of each pass
was severely restricted. If the ship was turned too sharply the gear
on the inside of the turn would sink and the wire may separate if the
gear bottomed. The gear on the outside of the turn would shear wildly
because of the increase in speed and the tow wire could separate under
the additional strain.
Starboard crane ready to lift a para vane
Attaching electrical cable used to power an acoustic device
Acoustic device on the left with a para vane on the right
The wire cables used to stream the mine sweeping gear are
shown on the winch drums. The electrical cable used to power
the acoustic device is shown above the drums resting on the rollers.