KN Values Analysis allows you to determine the hydrostatic properties of the hull at a range of heel angles and displacements to produce the cross curves of stability diagram.

Select KN Values from the Analysis Type option in the Analysis menu or toolbar.

The analysis settings required for KN Values analysis are:

§   Heel from the Analysis menu, select range for analysis

§   Trim (fixed or free) from the Analysis menu

§   Displacement from the Analysis menu, select range for analysis and specify estimate of VCG if known

The heel angles used may differ from those used in the Large Angle Stability and Limiting KG analyses. To set the range of angles, select Heel from the Analysis menu.

A range of displacements for KN calculations can be specified using the Displacement command from the Analysis menu. Initial and final displacements can be entered, together with the number of displacements required.

The VCG can also be entered (specified from the vertical zero datum). Traditionally, KN calculations are calculated assuming the VCG at the baseline (K). However if the analysis is being calculated free-to-trim and an estimate of the VCG is known, the accuracy of the KN calculations (for VCGs in the vicinity of the estimated VCG) may be improved by calculating the GZ curve using the estimated VCG position – this will reduce the error in the trim balance due to the vertical separation of CG and CB because this vertical separation is specified more accurately than simply assuming the VCG at the baseline.

If a VCG estimate is specified, the KN values are still presented in the normal manner with the KN values calculated as follows:

KN(φ) = GZ(φ) + KG_estimated sin(φ)

For information on Trim settings for KN Analysis, see: Trim for KN, Limiting KG and Floodable Length analyses on page 96.

Also see

KN Value Concepts on page 76

§   Density

§   Wave Form (if any)

§   Hog and Sag (if any)

§   Damage (or Intact) from the Analysis toolbar

The righting lever, GZ, may be calculated from the KN cross curves of stability (at the desired displacement) for any specified KG using the following equation: .

GZ = KN - KG sin(φ)

Note: KN values can also be referred to as “Cross curves of stability”.