Your vessel displaces 497 tons. The existing deck cargo has a center of gravity of 2.5 feet above the deck and weighs 24 tons. If you load 18 tons of ground tackle with an estimated center of gravity of 18 inches above the deck, what is the final height of the CG of the deck cargo?
• Combined center of gravity (KG) when adding weights on deck • Using the moment = weight × distance method to find a new KG • Remember that the vessel’s total displacement is not the same as the total deck cargo weight
• First, ignore the ship’s 497 tons and focus only on the existing deck cargo and the new ground tackle. What are the two weights and their individual KG’s above the deck? • Compute the moments for each deck load (weight × height above deck). How do you combine those to find a single equivalent KG for all deck cargo? • Once you find the combined KG in feet, compare it to the original 2.5 ft. Should the combined CG move closer to the lower load or the higher load?
• Be sure you ONLY use the 24 tons and 18 tons when computing the deck cargo CG, not the 497-ton ship displacement. • Convert 18 inches to feet before calculating moments. • After dividing total moment by total deck-cargo weight, confirm if the final CG is between the two original heights (2.5 ft and 1.5 ft).
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