Trailing or Walker Log

Definition

A rotator streamed on a braided line of perhaps 30 metres turns a mechanical counter mounted on the taffrail, reading distance in nautical miles. It requires no hull penetration and no electrical power, remains accurate over long ocean passages and is unaffected by fouling of the hull, which is why it survives as an offshore backup. Drawbacks include vulnerability to fish strikes and weed, and the need to recover it before manoeuvring astern.