Phases of the rowing stroke

Shown below is a figure illustrating how the blade forces (drag, lift, and propulsive) evolve throughout the drive. Also plotted is the instantaneous blade propulsive efficiency.

Looking at how the blade forces and efficiency change over time, as well as the path of the blade through the water, we can divide the stroke into three distinct phases.

Phase 1

• • Blade is moving away from the shell with a positive slip

  • Water approaches the blade tip at a shallow angle of attack and flows across the front (concave) and back (convex) faces of the blade without separating from the surfaces, promoting a high lift force and a low drag force

  • Lift dominates the propulsive force

  • Blade propulsive efficiency is at its highest

Phase 2

• • Blade continues to move away from the shell, but the slip is now negative

  • Water approaches the blade at an increasing angle of attack and flows along the front face of the blade, while the water separates from the back of the blade as it moves past the tip

  • The flow separation off of the back of the blade creates an area of swirling flow and an increased influence of drag force, while lift decreases

  • Propulsive force is at its highest, and the blade propulsive efficiency begins to drop

Phase 3

• • Blade begins to move back towards the shell, and the slip is negative becoming positive at the end of the drive

  • Water approaches the blade from the shaft-side, moving across the front face towards the tip, while reattaching to the back face

  • The region of swirling water behind the blade grows and moves farther from the surface, causing drag to dominate the propulsive force, which is low

  • Blade propulsive efficiency is low, but increasing slightly before dropping off

When we begin to understand of the underlying characteristics of these three phases, there are many equipment considerations and technique implications which can be made.