# Polars Chart

### 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 *0°* 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.