Optimizing VMG and Angles

Velocity Made Good (VMG) is the decisive metric for every course decision on the leeward leg when sailing downwind. Those who focus only on maximum boat speed often sail too deep and lose to competitors who choose the optimal wind angle course. Conversely, those who understand the relationship between True Wind Angle (TWA), boat speed and target direction systematically build a lead in regattas – without risky maneuvers or excessive gybing.

This guide explains how to optimize VMG and course angles downwind in practice: from the basic formula to wind-strength-dependent angles, crew communication and training methods. You can find the fundamental concepts under Courses and VMG; an overview of downwind sailing under Downwind Sailing.

What VMG Means Downwind

VMG describes the speed component toward the target – on the leeward leg, that means toward the next mark or target zone. Mathematically:

VMG = boat speed × cos(deviation from target course)

A boat at 7 knots on a course deviating only 10° from the direct route to the mark achieves a VMG of approximately 6.9 knots. Another boat at 9 knots but 35° off course achieves around 7.4 knots VMG – despite higher boat speed, it may reach the target more slowly depending on the situation.

Downwind, VMG optimization differs fundamentally from upwind sailing: instead of working against the wind, you use apparent wind to achieve the highest rate of progress through angles left and right of the direct course. The direct course (TWA near 180°) is rarely optimal.

Understanding True Wind Angle and Course Angle

The True Wind Angle (TWA) measures the angle between the bow direction and the true wind. Downwind, typical regatta courses range between 120° and 170° TWA:

1. TWA 120°–140° – "higher" downwind course, more speed, less direct toward target
2. TWA 140°–160° – common VMG optimum in moderate wind strength
3. TWA 160°–180° – deeper course, closer to target, often lower boat speed

Course Over Ground (COG) can deviate from the steering course due to current and waves. Helmsman and tactician must evaluate VMG based on actual movement over ground, not just compass course.

VMG Polars and Boat Classes

Every boat class has a characteristic VMG polar: a diagram showing the TWA with maximum VMG for various wind strengths. An ILCA 7 sails differently in 8 knots of wind than a J/70 with spinnaker or a 49er in planning mode. Polars come from:

• Manufacturer specifications and class association documentation
• Your own training with GPS and wind instruments
• Comparison with experienced sailors of the same class

Measuring VMG and Evaluating It in a Race

Modern regatta boats provide VMG values via GPS, wind instruments and software. For practical use, follow these steps:

1. Activate VMG display – set target mark or next gate as reference
2. Compare both gybes – hold left and right of course for 30–60 seconds each
3. Calculate average – filter out short fluctuations from waves and gusts
4. Log wind changes – link shifts and pressure zones with course changes
5. Recalibrate after maneuvers – test again after gybes or spinnaker sets

Communication Between Helmsman and Tactician

Clear calls prevent course chaos on the leeward leg:

• "Hold course" – current TWA delivers best measured VMG
• "5° higher" / "5° deeper" – systematic angle adjustment
• "VMG dropping" – immediate course change or trim correction needed
• "Gybe soon" – planned gybe to the better VMG side

The tactician watches pressure, competitors and laylines; the helmsman implements the recommended angle and reports boat speed and stability.

Optimizing Angles by Wind Strength

Light Wind: Sail Deeper, Maintain Area

In light wind, every VMG component toward the target dominates. Courses that are too high (smaller TWA) cost speed and leave the boat "stalling". Priorities:

• Open mainsail and headsail wide, set spinnaker early if planned
• Crew to windward for minimal wake in the water
• Gybe only with clear VMG advantage on the other tack
• Ride gusts by bearing away slightly (larger TWA)

Details on spinnaker use: Spinnaker Set and Drop

Moderate Wind: Finding the VMG Optimum

In 8–12 knots, active angle testing pays off. Sail alternately 5° higher and deeper and compare VMG over 30 seconds. Many classes show an optimum at 145°–150° TWA here. Observe:

• BS rising significantly, VMG falling? → sailing too high
• BS dropping sharply, VMG rising only minimally? → sailing too deep
• Adjust spinnaker trim and guy in parallel with course

Fresh Wind and Planning: Converting Speed into VMG

Planning dinghies and catamarans often achieve their best downwind VMG values at smaller TWA (130°–140°). Waves and surf phases deliver speed bursts that you convert into VMG by bearing away slightly afterward. Risks:

• Broach on too deep a course with full spinnaker
• Over-maneuvering through too frequent gybing
• VMG loss through uncontrolled direction changes

Sail Trim and VMG: An Inseparable Unit

Course angle and trim work together. A poorly trimmed spinnaker forces a deeper course and lowers VMG – regardless of helmsman talent.

Checklist: Check Trim Before Course Change

• Spinnaker luff not too far away (avoid curl)
• Guy tension appropriate for course
• Mainsail traveller and outhaul for stability
• Boat weight (crew position) for minimal wake
• No unnecessary drag from loose lines or incorrect sail handling

In broader winds and heavier boats, Gennaker and Code Zero supplement sail choice and shift the VMG optimum toward slightly higher courses.

Tactical VMG Decisions

VMG optimization is not just technique – regatta context changes the best course:

1. Laylines and gates – on windward-leeward courses, early approach to the leeward mark can override VMG strategy
2. Pressure and wind lines – more wind on the right can justify a higher course, even if the polar recommends "deeper"
3. Blanking competitors – brief bearing away on sailing-by-the-lee can sacrifice VMG but brings tactical advantage
4. Gybe timing – perform gybes under Gybing and Tacking only when the new tack promises measurably better VMG

Common Mistakes and How to Avoid Them

Typical VMG killers downwind:

1. Sailing too deep – high BS reading deceives; VMG toward target remains low
2. Measuring too rarely – once-found optimum does not apply to all wind conditions
3. Neglecting trim – treating course as the only control
4. Gybing from panic – gybes without VMG advantage cost 2–4 boat lengths
5. Instrument blind flight – numbers without feel for balance and stability

Checklist Before the Leeward Leg

• Wind strength and shift tendency aligned with tactician
• VMG reference set to next mark
• Spinnaker/trim prepared for expected TWA
• Plan for first gybe side (left/right) established
• Competitor position and blanking options discussed

Training: Building VMG Awareness Systematically

An effective training program for VMG and angles:

1. Collect polars – 3–5 runs of 2 minutes per wind strength, vary TWA
2. Gybe comparison – same conditions, which tack delivers higher average VMG?
3. Sail without instruments – develop feel, then verify with GPS
4. Roll gybe under speed – clean gybes without VMG drop (see Roll Tack and Roll Gybe)
5. Regatta simulation – leeward leg with gate and competitor boat

Frequently Asked Questions About VMG Downwind

• Is the deepest course always fastest to the target? – No, VMG depends on the angle.
• How often should I gybe? – Only when the other tack delivers measurably better VMG.
• Which TWA is universally optimal? – None – depends on boat class and wind strength.
• Do I need expensive electronics? – Helpful, but pair training is enough to get started.
• Prioritize VMG or speed? – Always VMG toward the target mark.

Summary

Optimizing VMG and angles downwind means finding the fastest rate of progress toward the target – not the highest knot reading on the display. The optimal TWA shifts with wind strength, boat class, trim and tactical situation. Those who measure, communicate and train systematically make better decisions on the leeward leg than competitors who "simply sail down". Combine polar knowledge with regatta tactics and solid apparent wind understanding – then the leeward leg becomes a strength instead of a gamble.

Related Topics

• Downwind Sailing
• Courses and VMG
• Upwind and Apparent Wind
• Windward-Leeward Courses
• Spinnaker Set and Drop