Propeller Walk

A sideways tendency of a vessel’s stern caused by transverse forces from a rotating propeller.

Also called transverse thrust or prop walk, it is often most noticeable when applying astern power at low speed before useful water flow reaches the rudder. Direction and strength depend on propeller rotation, shaft angle, aperture, hull and rudder geometry, water depth and whether power is ahead or astern.

The effect can assist or oppose close-quarters manoeuvring but should be established experimentally in controlled conditions rather than assumed from a generic right- or left-handed rule. Wind, current, momentum and propeller wash can dominate or modify the observed motion.