The Heel dialog from the analysis menu is used to specify the range of heel angles to be used for Large Angle Stability, KN and Limiting KG analyses. Heel angles between -180° and +180° may be specified. The heel steps must be positive. If only one set of steps is required, simply put 0 in the other steps.
If there is any asymmetry in the vessel due to either: hull shape, key points, loading, damage, etc., and there is any doubt as to which will be the worst heel direction, then the analysis should be carried out for both heel to starboard and heel to port to find the most pessimistic condition.
If all the heel angle intervals are 10 deg or less, Hydromax will fit a cubic spline to the GZ curve and use this to interpolate for values between the tested heel angles. If any step is greater than 10 deg, Hydromax will not do any curve fitting and linear interpolation will be used.
Note:
For
the angle of equilibrium to be found (when analysing criteria), it is essential
that the GZ curve crosses the GZ=0 axis with positive slope. It is possible
that the GZ at zero heel may be very slightly positive (due to asymmetry or
rounding error) for this reason, it is advisable to test at least one negative
heel angle, at say -5 degrees, to ensure that the equilibrium angle is
identified.
It is good practise to start the heel range at an angle of approximately -30°.
This is to allow roll back angle criteria to be evaluated correctly.
Note:
The heel angles to be used are specified independently for each analysis mode. This can be a source of apparent differences in the results from the different analyses.