Start-line bias — favoured end wins
On a pin-favoured line, the boat off the favoured end reaches the windward mark first. The gap is the advantage.
Both boats start on port at opposite ends of a pin-favoured line and beat to the same windward mark. The pin end is further upwind, so the green (pin) boat has less distance to sail and lays the mark while the red (committee) boat is still climbing — that gap is the bias advantage. Toggle the Start-line bias arrow to read it in degrees, or turn the wind / drag a mark and watch which end becomes favoured. Same speed for both — the only difference is where they started on the line.
Opens the animation on the boat-length grid — scrub it, edit it, or use it as a starting point. Free, no account needed.
How it interacts with other rules
- Rule Lab — Kinematic beat — laylines, bias & shift · see also
Square line + a timed wind shift.
- Rule 11 — Shutting the Door at the Pin · see also
Starting at the pin end.