For most analyses you may specify whether the vessel is free-to-trim or has fixed trim. Select Trim in the Analysis menu to bring up the Trim dialog.
Specification of different trim options is dependent on the type of analysis currently selected.
Trim may be specified for Upright Hydrostatics, Large Angle Stability, KN Analysis Limiting KG, Floodable Length and Tank Calibrations. (For the Specified Condition analysis, the trim may be specified in the Specified Conditions dialog.) Equilibrium and Longitudinal Strength analyses always use a free trimming (and free heeling) analysis so that there is no trimming (or heeling) moment applied to the vessel at the final equilibrium.
(KN and Limiting KG analyses only).
The analysis is carried out with the specified fixed trim; the vessel is not free-to-trim as it heels. Although considerably faster, this analysis will tend to over-estimate ship stability properties such as GZ.
Free-to-trim using a specified initial trim value
Using this method, for each displacement, the LCB of the intact vessel at the specified trim and zero heel is computed. The LCG is calculated using this value and the VCG. Calculations at each heel angle of the large angle stability analysis are then done free-to-trim using the derived LCG and VCG. Thus, for each displacement, the upright, intact vessel trim will be the same, but the LCG will be different.
Free-to-trim to a specified LCG value
With this method, a specified constant LCG is maintained for each displacement. This LCG is then used to compute the free-to-trim vessel orientation at each heel angle as the large angle stability analysis is performed. Thus, for each displacement, the LCG will be the same, but the upright vessel trim will be different.