Start Line Bias Calculator
Compute signed start line bias from biasSeconds = (lineLengthNm * 3600 / boatSpeedKt) * cos((lineBearingDeg - trueWindFromDeg) * PI / 180); positive favors the pin end.
Description
Compute signed start line bias from biasSeconds = (lineLengthNm * 3600 / boatSpeedKt) * cos((lineBearingDeg - trueWindFromDeg) * PI / 180); positive favors the pin end.
Start Line Bias Calculator is a focused tool for the following task. Compute signed start line bias from biasSeconds = (lineLengthNm * 3600 / boatSpeedKt) * cos((lineBearingDeg - trueWindFromDeg) * PI / 180); positive favors the pin end. It reports Line bias from the values you provide rather than inventing measurements, coefficients, or professional judgment that are not part of the input.
When to use Start Line Bias
Use this sailing calculation for planning or education when the vessel, units, reference directions, environmental conditions, and assumptions are explicitly known.
- Line length (nm)
- Required number in nm. Length of the starting line.
- Boat speed (kn)
- Required number in kn. Boat speed for the beat upwind.
- Line bearing (deg)
- Required number in deg. Compass bearing of the starting line from committee boat to pin.
- True wind from (deg)
- Required number in deg. Direction the true wind blows from.
The cited overview of Navigation supplies background for the terminology and domain context used by this tool.1
How Start Line Bias works
Compute signed start line bias from biasSeconds = (lineLengthNm * 3600 / boatSpeedKt) * cos((lineBearingDeg - trueWindFromDeg) * PI / 180); positive favors the pin end. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.
- Line bias (s)
- Returned number in s. Signed time advantage in seconds; positive means biased to the pin end.
Limitations and assumptions
- Vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, and safety margins can make real conditions differ from a simplified result.
- Line length must be at least 0.
- Boat speed must be at least 0.
- Line bearing must be at least 0.
- Line bearing must be no greater than 360.
- Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.
Alternative or Complementary approaches
Cross-check current charts, tide and weather services, instrument data, vessel manuals, and applicable navigation rules, and retain a conservative alternative plan.
References
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Navigation — Wikipedia contributors
Similar or alternative tools
- Favored End Calculator
Identify which end of the start line is favored by comparing the time to sail the line against the true wind direction.
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- Current Correction Angle Calculator
Compute the signed crab angle needed to oppose a current's cross-track component. Routes whose cross-current exceeds boat speed cannot be held.