Orca3D News


Thursday, May 21, 2015

Defining Limits for Stability Criteria Verification

Orca3D's Work-in-Progress (WIP) version contains a module for evaluating stability criteria. One of the basic steps is to define the limits for the evaluation. When defining limits for stability criteria verification, you may of course enter some absolute figures of angle, area, righting arm, etc. A simple limit could be:


        Angle At GZmax >= 25 deg
However, Orca3d offers extended limit definition capabilities, by allowing the user to input mathematical operations, and to use the vessel’s dimensional characteristics or hydrostatic properties to compose even the most complex criteria sets.
For example, the ISO standard 12217-1 for small craft will ask for verification that the heel angle is not greater than a value which is a function of the vessel’s length (§6.2.3 of the standard):
This limit angle may be defined in Orca as follows:
Mathematical operations may also be used to define the angle at which the evaluation is done. In the example above, the evaluation is done at "SteadyEquil" but you may also enter an expression such as "SteadyEquil - 10."
The table below is a list of the keywords which may be used in the expressions.
Lwl
Displacement
Bwl
Volume
Draft
Wet Area
Loa
Sinkage
Boa
Trim
Depth
List
LCB
Cb
TCB
Cx
VCB
Cp
LCF
Cvp
TCF
Cwp
VCF
Cws