100 years ago today: Preparing to detect enemy submarines on the ocean floor.
On this day 100 years ago, a 500-foot roll of phosphor-bronze wire was invoiced for submarine chaser SC 354. The new U.S. submarine chasers were being fitted with the latest antisubmarine invention, the trailing wire.
A known tactic of the U-boat captains was to set the submarine on the ocean bottom and "play dead" when Allied vessels were nearby. The trailing wire was designed for detecting stopped submarines. Subchasers or other vessels fitted with the device would unreel the phosphor-bronze wire into the water, a weight attached to the end to make it sink. When the wire struck a metal object such as a submarine hiding on the bottom, a small electric current traveled up the wire and activated an annunciator. Should a chaser captain suspect a submarine to be hiding on the ocean floor, he would order the deployment of the trailing wire, and the crew would run the chaser back and forth over the spot with the trailing wire extended.
Early photos of chasers show the phosphor-bronze reel on the stern. (See Hunters of the Steel Sharks: The Submarine Chasers of WWI, page 43 for an example.) But this was among the devices that proved to be impractical, especially in deep waters such as in the Strait of Otranto. The devices were soon removed, and there are no reports from the chaser fleet indicating a detection of a submarine using the trailing wire.