You are on a supply run to an offshore drilling rig. You are carrying the load show in table ST-0015 below. What is the height above the main deck of the center of gravity of the cargo? I. Two reels of hoisting wire. Each reel is 8 feet in circumference and 4 feet wide and has 3000 feet of wire. Both reels are stowed on the flat. Wire weighs 1.55 pounds per linear foot. The tare weight of each reel is 500 pounds. II. Eight pallets of case goods stowed singly. Each pallet is 8' L X 4' W X 4' H and weighs 1 long ton. III. 12 steel containers of cement. Each container weighs 1 1/2 tons. Each container is 8' L X 4' W X 4' H. The containers are stowed singly fore and aft. IV. 10 crates of stewards stores. Each crate measures 4' L X 4' W 3' H and weighs 420 pounds. Each crate is stowed on deck.
• Center of gravity (KG) of each cargo group based on its own height above deck • Using weighted average: total moment ÷ total weight to get overall KG • Interpreting phrases like "stowed on the flat" and using circumference to find the reel’s radius (and thus its CG height)
• How do you find the height of the CG of each type of cargo (reels, pallets, containers, crates) measured from the main deck? Where is the midpoint of each piece? • Once you know the CG height and weight of each group, how do you combine them to find a single overall cargo CG? • For the reels, how can you use the given circumference to compute the reel’s radius, and what does that tell you about the CG height when the reel is lying on its side on deck?
• Be sure to convert all weights into the same units (either all pounds or all long tons) before computing moments. • For the reels, confirm you included both the wire weight and the tare weight of the drum when finding the total weight. • Before choosing an answer, re-check that you computed total moment = Σ(weight × CG height) correctly and then divided by total cargo weight to get the final KG above the deck.
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