LIMIT commands for a variable area criterion.


Question:

Given the following criteria how would I write a limit command to satisfy the
equation ?


        An area under each righting arm curve up to the angle of maximum 
        righting arm of not less than the area determined by the following 
        equation:  A = 10.3 + 0.187 (30-Y) at max RA.


Answer:


It takes two consecutive LIMIT commands to handle this criterion:
    
  LIMIT(1) AREA FROM 0 TO MAX AT 15 > 13.1                                                      
  LIMIT(2) AREA FROM 0 TO MAX AT 30 > 10.3                                                      
    
These are mentioned in the manual under the LIMIT command in the Command
Dictionary.
    
Syntax Notes:
1) These two limits must be consecutive; e.g. 1 & 2 as above.
2) The /LIMIT:COMBINE subparameter must also be used on any RA command
where the two limits are to be evaluated as a single varying limit.

The interpretation is that the limit value is 13.1 when the angle of MAX is at
15°, 10.3 when   it is at 30° and a linear interpolation between 13.1 and 10.3
when it is between these angles.

Keywords: Offshore Supply Vessel Criterion, IMO A.469 2.5.2