Polars Chart


A Polars Chart is generally represented in a semi-circle Scale (180°). This is because modern boats have symmetrical performances, thus behaving similarly whether the wind comes from port side (left) or from starboard (right).

The Scale

A polar scale is built upon 2 dimensions:

The angle must be read from the top (0°) to the bottom (180°), and represents the TWA.

The distance to the center represents the Boat Speed.


On the example beside, the angle is 35°, and the corresponding boat speed equals 6.02 kts.


The Boat Speed axis might rescale if the plotted curve becomes too narrow or too large as the TWS varies.

The Curve

The curve is a summary of the best speed at every angle.

Each color represents the sail producing the best speed for a given angle and for the TWS provided in the input field.

The best sail for a given angle is also displayed in the Sails panel where the bold line has the same color.

It is possible to draw one curve per sail by checking the Plot Full Sails Curves option on the Sails side panel.

Best VMG

Please read this section first if you don't know what the VMG is.

The VMG can be visually represented on the chart thanks to the VMG Projection to Axis in the Attitude panel.

The VMG projection option will draw a red dotted horizontal line, showing the effective amount of speed pushing the boat in the wind direction.

At the two angles where VMG is best (upwind or downwind), a red dashed line represents the Best VMG.
Also, the portion of the Chart between and Best upwind VMG on one side, and Best downwind VMG and 180° on the other side, are fulfilled in pale red because they are almost never a good idea to sail at those angles.

On the example beside:
    (1) is the VMG Projection,
    (2) is the underperforming zone below Best VMG,
    (3) is the Best Upwind VMG angle.