Your vessel displaces 14,500 tons, with a longitudinal CG 247.5 ft. aft of the FP. If you pump 80 tons of ballast from forward to aft through a distance of 480 feet, your new CG will be __________.
A. 244.85 feet aft of FP
B. 246.22 feet aft of FP
C. 248.87 feet aft of FP
D. 250.15 feet aft of FP
A. 244.85 feet aft of FP
B. 246.22 feet aft of FP
C. 248.87 feet aft of FP
D. 250.15 feet aft of FP
This is a multi-step problem. First thing to recognize is that is a shift of weight problem so the Displacement will not change because we are not loading or discharging. Second thing to keep in mind is the Center of Gravity will move in the direction of the shift which in this case is AFT. A sketch of the problem will always help you map out you plan of attack!
ReplyDeleteReference: STABILITY AND TRIM FOR THE SHIP'S OFFICER, 4th Ed,
pages 55 to 59, GG' FORMULA
For a shift of a single weight we can use GG' = weight x distance / Final Displacement
Where:
Weight = 80 tons
Distance = 480 feet
Displacment = 14,500 tons
GG' = Shift of G (Aft in this case)
GG' = 80 tons x 480 feet / 14,500 tons = 2.65 Feet AFT
Original LCB = 247.5 feet AFt of FP
+ Shift = 2.65 feet Aft
New LCG = 250.15 feet aft of FP
Best answer is Choice D.
Shift of G formula:
ReplyDeleteGG'= W*D/Displacement
80*480/14500=2.65-ish
moving the weight from froward to aft, L.C.G. will move aft.
247.5+2.65=250.15 Ft. aft of the F. Perpendicular
ANS: DELTA