The polar diagram plots boat speed (BSP) against true wind angle (TWA) for different wind speeds. Each curve shows how fast the boat goes at each angle — the further from center, the faster.
Wind angle/speed cells with fewer than 5 raw readings are dropped from the curve entirely rather than drawn — a single instrument or GPS glitch in an otherwise near-empty cell would otherwise render as a full-weight spike far outside the smooth, well-sampled shape around it.
Each wind angle/speed cell contains many individual BSP readings from past sessions. The slider controls which value from that distribution is used to draw the curve:
Avg — the mean of all readings in the cell. Reflects typical speed, pulled down by slow moments.
P75 — 75% of readings were at or below this speed. A conservative but reliable target.
P85 — the default. A good balance between achievable and realistic peak performance.
P95 — near the top of what's been recorded. Represents a very good sail.
Max — the single fastest reading ever recorded in that cell. May include gusts or instrument spikes.
Curves — connects the BSP data points for each wind speed bin into a smooth line.
Smooth — applies a 3-point weighted average across adjacent wind angles to reduce noise.
Scatter — plots every individual raw data point instead of a summarized curve.
Each colored button toggles a wind speed band on or off. Click any button to isolate specific conditions — useful for comparing performance at different wind strengths.
The MM Reference Polar is the boat's theoretical target boat speed for a given wind angle and wind speed — the same table used by the "MM Reference Polar" source in the dropdown above. This overlay superimposes it on whatever view you're currently looking at, so you can compare directly instead of switching sources back and forth.
Each active TWS band gets one dashed target line with diamond markers, matched to the nearest discrete wind speed the reference table actually has data for (it's a sparse ~165-point grid at fixed TWS values like 6, 8, 10, 12… — not every band has an exact match). Where the empirical curve sits inside its target line (closer to center), that's a real speed gap at that angle.
A gybe is detected as a Twa sign-flip while sailing broader than 100° on both sides; a tack is the mirror image — a sign-flip while sailing narrower than 80° on both sides. Either way the flip must complete within 3 minutes, so two unrelated same-side periods hours apart aren't mistaken for one continuous maneuver. "Omit" excludes every point within ±2 minutes of each detected event, both gybes and tacks together (this page shows the whole polar at once, not a single point-of-sail view).
Why it might matter: mid-maneuver, boat speed stalls then surges (or the boat luffs near head-to-wind) — readings that aren't representative of steady-state sailing at that angle. Those transient points land disproportionately in already-thin cells, where a couple of stalled or transitional readings can swing the average and spike the curve. First caught this on the 25° TWA / 10-15kt cell — two near-stalled TransPac 2017 readings (0.6, 2.66kt) mixed into a small sample was enough to distort the percentile curve.