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

Forestay tension (N)

Required number in N. Tension in the forestay.

Forestay angle (deg)

Required number in deg. Angle between the forestay and the mast at the hounds, in degrees.

Shroud angle (deg)

Required number in deg. Angle between the cap shroud and the mast at the hounds, in degrees.

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

Compute the cap-shroud tension needed to balance a given forestay tension from the rigging head angles. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Shroud tension (N)

Returned number in N. Required cap shroud tension.

• 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.
• Forestay angle must be at least 5.
• Forestay angle must be no greater than 175.
• Shroud angle must be at least 5.
• Shroud angle must be no greater than 175.
• 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.

• Boom Force Calculator

  Compute the compression force on the boom from sheet tension via torque balance about the gooseneck.

• Bowsprit Compression Load

  Compute the ideal axial compression required to balance a forestay load at a specified angle to the deck.

• Anchor Rode Length Calculator

  Compute the anchor rode length needed from water depth, freeboard, and scope ratio.