Diagram of Orepesa sweep

A method of minesweeping developed in World War I and named after the trawler that first practised it.

The Sweeper and her Sweeping Gear

It is the sweep wire curving back from the trawler to the otter that does the work. In the black part of the diagram, where everything you see is under the water, the sweep wire cuts the mooring cables of the mines. They then bob to the surface, and are exploded by gunfire — unless the sweep wire has already exploded them. In the diagram one mine has been severed and the mooring cable of another is being cut. The otter and kite work on the principle of air kites; the kite holds the inboard end of the sweep wire down; the otter, suspended from the flagged torpedo-shaped float, takes the sweep out on the trawler's quarter... Balls at the masthead show that sweeping is in progress.
Extract and diagram from His Majesty's Minesweepers, His Majesty's Stationery Office, 1943, Crown copyright (expired).
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