You have 10 containers of rig supplies each measuring 10'L by 6'B by 6'H and weighing 1.8 tons each. Each container is stowed on deck. What is the maximum VCG permitted of the remaining cargo if you are carrying rig water and load to maximum capacity? See illustration D037DG below.
• Use the stability letter restriction that the height above the main deck of the center of gravity of ALL deck cargo shall not exceed a certain value (see item 3 in D037DG). • When rig water is carried, the maximum total deck cargo weight is reduced (see item 4 in D037DG). • Use the combined center of gravity formula: total moment divided by total weight, and set this equal to the maximum allowed CG height to solve for the unknown VCG of the remaining cargo.
• First, when rig water is at maximum capacity, what is the maximum deck cargo weight you are allowed to have? How much of that is already taken up by the 10 containers? • What is the VCG of the 10 containers above the deck, based on their height and how they sit on deck, and what is their total moment? • If the combined CG of all deck cargo cannot be higher than the limit in the letter, how can you use the total weight and known moments of the containers to find the maximum possible VCG of the remaining cargo?
• From the stability letter, verify the exact maximum height of the deck cargo CG above the main deck (in feet). • Confirm the total weight of all 10 containers in long tons and that this weight plus the remaining cargo does not exceed the deck cargo tonnage limit when rig water is carried. • Make sure your final combined CG calculation uses total moment = (W1×KG1) + (W2×KG2) and total KG = total moment / total weight, and that this total KG does not exceed the stability letter limit.
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