Route on your boat, not a generic cruiser

A polar is your boat's performance map: for each true wind speed and each angle off the wind, the boat speed she can actually sail. Plotted radially it looks like a set of nested curves — dead upwind at the top, dead downwind at the bottom. Every serious routing decision (when to tack, whether the reach is worth the extra miles, what your ETA really is) is a polar lookup.

Pick your production model at signup and OpenSail attaches a catalog-estimate curve immediately: a physics-scaled cruiser curve derived from the model's published specifications (hull type, waterline-based hull speed, and sail-area-to-displacement ratio). It is honestly labeled an estimate — a plausible curve for that model, never passed off as measured data — and it routes far better than the generic default every other product silently uses.

Because for most cruising boats there isn't one. Very few builders publish measured polars; what exists is scattered across ORC certificates for raced hulls, sailmaker VPP runs, and class associations — each with different assumptions about sails, load, and sea state. Where an owner has any of those, OpenSail imports the file directly. Where nobody has one, an honest labeled estimate beats a confident fabrication.

Yes — POL, CSV, TXT, and JSON files import with an instant diagram preview, including sailmaker exports with semicolon or tab layouts and European decimal commas. Malformed files are rejected loudly at save with a plain-language reason, never silently misread — a shifted column in a polar is worse than no polar.

Every polar opens as an editable table — boat speed per wind speed and angle — with the diagram redrawing as you type. Fill in what you know; blank cells are completed by interpolation at save, and the diagram always shows exactly the table routing will use. Nothing you entered is ever silently dropped.

The Rust isochrone solver reads the full two-dimensional table — every wind speed, every angle — and interpolates between cells for each candidate heading, thousands of times per route. It is not a hull-speed cap or a single number: the shape of your curve is what decides when the solver tacks, how wide it sails the downwind angles, and what ETA it commits to.

Enter her basic specs and OpenSail estimates a starting curve from naval-architecture ratios, clearly labeled as estimated. She routes the same day; refine the polar whenever you have better numbers.