Use this sailing calculation for planning or education when the vessel, units, reference directions, environmental conditions, and assumptions are explicitly known.

Wind speed (kn)

Required number in kn. Current wind speed.

Max wind (kn)

Optional number in kn. Maximum working wind for the boat, between 10 and 60 knots.

The cited overview of Running rigging supplies background for the terminology and domain context used by this tool.^[1]

Suggest vang tension from vangPercent = min(100, max(10, round(windSpeedKt / maxWindKt * 100))) using the boat's maximum working wind. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Vang tension (%)

Returned number in %. Recommended vang tension as a percentage of range.

• 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.
• Wind speed must be at least 0.
• Max wind must be at least 10.
• Max wind must be no greater than 60.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Cross-check current charts, tide and weather services, instrument data, vessel manuals, and applicable navigation rules, and retain a conservative alternative plan.

• Backstay Tension Guide

  Suggest backstay tension from backstayPercent = min(100, max(10, round(apparentWindKt * 4))).

• Cunningham Tension Guide

  Suggest cunningham tension from cunninghamPercent = min(100, max(0, round((apparentWindKt - 8) * 6))).

• Jib Lead Angle Guide

  Suggest jib lead angle from leadAngleDegrees = min(25, max(5, round(apparentWindKt * 0.8))).