About LIMIT with three terminating angles


Question:

What limit commands would best address the following criterion:

  At least 15 foot-degrees of area to the smallest of the following angles.
  i) Angle of maximum righting arm
  ii) Angle of downflooding or
  iii) 40 degrees


Answer:

    
  LIMIT (1) AREA FROM 0 TO MAX OR FLD > 15                                                           
  LIMIT (2) AREA FROM 0 TO MAX OR ABS 40 > 15                                                        
    
This is preferable to the following:
    
  LIMIT (1) AREA FROM 0 TO MAX > 15                                                                  
  LIMIT (2) AREA FROM 0 TO FLD > 15                                                                  
  LIMIT (3) AREA FROM 0 TO ABS 40 > 15                                                               
    
The reason for this is that it is possible for the FLD angle and/or 40° to be
later than the second intercept.  Of course the area to MAX would be the
critical one in this case, but since the area starts to decrease after the
second intercept it is possible that the area from 0 to FLD, for example,
would be less than from 0 to MAX.  By including MAX for each limit, you
avoid this possibility.
    
Note that "0" in the above limit commands is relative to the initial angle
which you can set with the HEEL command or SOLVE command before doing the RA
command.  If you want to always begin the areas at equilibrium, substitute
"EQU" for "0".  If you always want to begin the areas at absolute 0 (upright),
substitute "ABS 0".