`Finding the angle Theta3, where A2 = A1 as in the RINA Cargo Loss criterion.
`In this run file, the TCG of the vessel is set to create conditions during
`lifting and after the cargo loss.  Since the effect of TCG varies with the
`cosine of the heel angle it is equivalent to setting a cosine based heeling
`moment.
`When using this method, the run file should either set up actual loading
`conditions with and without the crane load, or use a heeling moment to represent
`the counterballast weights.  Keep in mind that the equilibrium angle during
`lifting is saved as variable t1 and is necessary to evaluate the criteria.

proj theta3
read subdivy
crt(1) Vent 25a, 5s, 11 /sym
report
draft 6
vcg 8
solve weight lcg

macro findt3            `finds Theta3, then evaluates RINA Cargo Loss
 macro t3               `incrementally adjust t3 until t < 0.05
  lim title --Find Angle Theta3----------
  lim(1) res ratio from abs {t1} to abs {t3} > 1
  ra /lim /noprint
  \limmarg: {limmarg};  t3: {t3};  t: {t}  `prints iteration history
  if {t} < 0.005 then exit
  if {limmarg}>0 then set t3={t3} minus {t} else set t3={t3} plus {t}
  set t={t} times 0.5
  exit t3
 //
 variable t3=30         `theta3-terminating angle for res ratio limit
 variable t             `amount to increment or decrement t3
 set t={t3} div 2
 lim off
 .t3
 \\Theta3 is {t3:1} degrees, as demonstrated below.\
 \
 ra /lim:att /graph:none `/stop:fld
 if {t3}>30 then set t3=30 | ,,
 \Theta3 not to be taken greater then 30, therefore Theta3=30\
 page
 lim off
 limit title RINA Pt E, Ch 19, Sec 2: 2.2.3
 lim(1) res ratio from abs {t1} to FLD or RA0 > 1
 lim(2) angle from abs {t3} to FLD or RA0 > 20
 ra /lim:att /stop:fld
/

tcg=.5                  `Simulate lifting condition - hook load on starboard side
solve
variable t1={heel}      `Equilibrium heel angle during lifting

tcg=-1.5                `Simulate dropped load condition - counterballast on port side
so
`Setting angles direction and sign of starting angle, t1, if RAH to port.
`(Righting arm direction is determined by equilibrium angles before and
` after the hook load is dropped.  When the righting arm is to port, ABS
` angles are the opposite of the normal sign convention, which is +=STBD.
` Angles * is not sufficient to direct the righting arm direction for all
` combinations of equilibrium with and without lifting.)
if {t1}>{heel} then angles 0 -5 ... -30 | set t1=minus {t1},,
               else angles 0  5 ...  30
.findt3

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