Use this sailing calculation as a planning or educational cross-check for navigation, wind and current, rig loads, stability, anchoring, tides, visibility, performance, or recovery under explicitly stated conditions.

Apparent wind (kt)

Apparent wind speed the halyard must hold.

Guide mainsail halyard tension using a rule of thumb of twelve kilograms force per knot of apparent wind converted to newtons. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Halyard tension (N)

Recommended mainsail halyard tension in newtons.

• Actual conditions change with vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, regulations, and safety margins. Simplified formulas do not replace seamanship, approved stability data, or current navigation information.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Cross-check official charts, tide and weather services, instrument data, vessel manuals, and collision regulations; maintain conservative margins and a safe alternative plan.

• Jib Halyard Tension Guide

  Guide jib halyard tension using a rule of thumb of eight kilograms force per knot of apparent wind converted to newtons.

• Outhaul Tension Guide

  Suggest increasing outhaul tension as apparent wind rises, from twenty percent in very light air to full tension at twenty knots.

• Beaufort Scale Lookup

  Look up the Beaufort wind force from zero to twelve for a wind speed in knots using standard inclusive upper bounds.