proj crane

`A crane barge energy calculation simulating the sudden loss of a hook load
`ignoring damping -- following 46 CFR 173.025.

`Create a simple rectangular barge hull:
units lt

enter pm
create hull
ends 0 100
top 6
bot 0
out 30
/
write
quit pm

report

`Lightship weight & CG:
draft 4
vcg 12
solve weight, lcg

`Add counterbalance and hook loads:
boom "counter" 100 50 0 15 20 -90 0
boom "load" 40 50 0 11 80 90 10

`Macro to show initial status:
macro stat1
solve
page percentage 75 `minimum percent of page free to continue printing on page.
\\\===== Before hook load is dropped =====\
status
/
.stat1

`Delete hook load:
delete "load"

`Macro to do calculations for the present case after dropping load:
macro stat2
solve trim `solve without changing heel
\\\===== After hook load is dropped and before heel changes =====\
status
page
\\\
\ Note: The following righting arm curve represents heeling to port after
\ the hook load is dropped.
ra 0, -2, ... -30 /area:1-RA /stop:RA
/
.stat2


`An equivalent method using heeling moments:

delete all weights
add "counter" 100 50 0 15 `on centerline
add "load" 40 50 0 24.89 `on centerline
hmmt 1151.38 /c1 `<-- load minus counterweight

.stat1

delete "load"
hmmt -2000 `/c1 `<-- counterweight only

.stat2

`Finding max. VCG that meets energy requirement,
`assuming maximum initial heel angle of 3 degrees:

lim area from ABS -3 to RA0 or FLD > 7.0
angles 0 2
vcg = 0

`Compute max VCG curve given a range of drafts:
page
maxvcg 3 3.25 ... 5

`Find max VCG in present condition:
st
solve
angles *
ra/lim
solve maxvcg /fixdir `Keeps the heel direction from changing when solving for maximum VCG

`Verify max VCG:
page percentage 75 `minimum percent of page free to continue printing on page.
\\--- At maximum VCG ---\
ra /lim /stop:ra

print preview

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end