Guide

VMG analysis for sailing: what to review and what to ignore

VMG helps sailors understand progress toward the windward or leeward objective, but it only works when it is read alongside wind direction, heading stability, and manoeuvre timing.

Takeaway 1

Use VMG to compare progress toward an objective, not as a replacement for boat speed.

Takeaway 2

Compare similar points of sail and wind conditions before drawing conclusions.

Takeaway 3

Look at what happens before and after tacks or gybes because recovery time often explains VMG loss.

What VMG tells you

Velocity made good measures how effectively the boat is moving toward a target direction, usually upwind or downwind. Two sailors can show similar boat speed while one makes better progress because they sail a more effective angle or lose less ground during transitions.

That is why VMG is useful for training review. It connects speed and direction into a single question: did this mode actually move the boat toward the goal faster?

Where VMG can mislead

VMG is sensitive to wind direction assumptions. If the wind shifts during a session, an upwind leg that looks weak may have been sailed in a different tactical situation. For fair comparisons, use weather context and compare repeated legs that faced similar breeze and course objectives.

Short windows can also mislead. A sailor may show strong VMG for a few seconds before a bad tack, or weak VMG immediately after a gybe while the boat accelerates. The useful pattern is the sustained trend and the recovery curve after changes in direction.

  • Avoid comparing upwind and reaching work as if they answer the same question.
  • Treat very short spikes as signals to inspect, not final conclusions.
  • Check whether the fastest angle is also repeatable across the session.

A practical VMG review workflow

Start by marking the main upwind and downwind sections. Then compare VMG across sections with similar conditions, noting whether losses happen during straight-line sailing, manoeuvre entry, or acceleration out of the turn.

Use the outcome to choose a focused drill. If VMG loss clusters around tacks, work on entry speed and exit angle. If the loss appears on long straight sections, review trim, steering consistency, and target angle instead.