KN values or Cross Curves of Stability are useful for assessing the stability of a vessel if its VCG is unknown. They may be calculated for a number of displacements before the height of the centre of gravity is known. The KN data may then be used to obtain the GZ curve for any centre of gravity height (KG) using the following formula:

GZ = KN - KG  * sin(Heel)

where GZ is the righting lever measured transversely between the Centre of Buoyancy and the Centre of Gravity, and KG is the distance from the baseline to the vessel's effective Vertical Centre of Gravity.

KN Values Analysis Requirements

§   Range of displacements to be analysed

§   Range of heel angles to be analysed

§   Trim (fixed or free)

§   Estimate of VCG (provides more accurate result if free-to-trim)

KN Values Analysis Options

§   Fluid Densities

§   Wave form

§   Hog and sag

§   Damage

§   Tank and Compartment definition (in case of damage)

Output is in the form of a table of KN values and a graph of Cross Curves of Stability.

If the analysis is performed free-to-trim and an estimate of the VCG is known, this may be specified. The computed KN results will then give a more accurate estimate of GZ for KG close to the estimated VCG since the effects of VCG on trim have been more accurately accounted for.

For more detailed information please see KN Values Analysis on page 75.