The U.S. Coast Guard Museum, Seattle, Washington

Taffrail Log

Taffrail Log - US Coast Guard Museum - Seattle

Taffrail Logs were used to indicate the speed of a vessel. The propeller was attached to a line and then trailed behind a vessel. The turning of the propeller drove a gear train and pointer in the readout head. An hour glass was used to measure the time and the speed was then calculated using the distance traveled as indicated on the dial.

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