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DSK wrote: wrote: Maybe I've killed too many brain cells over the years or just forgotten some basic stuff but my understanding of Archimedes Principle is that the buoyant force on an object is equal to the weight of the fluid it displaces. Yep. ... This means that my boat that weighs 8000 lbs must displace 8000 lbs of water in order to float. Yep. ... If she takes on 8000 lbs of water, she sinks cuz the buoyant force doesnt balance the weight. Right? Not necessarily. There is a relationship between weight, displacement, and immersed volume. The "displacement" in reality is the immersed volume, and the weight of that water *will* equal the actual weight (or mass would be a better term) of the boat & all it's contents. So, if your boat weighs 8000#, and you add another 8000# (doesn't matter if it's inflooding water, bricks, or feathers) then your boat might sink *if* it does not have the hull capacity to create that new larger immersed volume, and thus displace that much more water. Capische? So, why do people make a distinction 'tween displacement and weight? Usually what people mean by "displacement" is shorthand for 'displacement when floating at the boat's designed waterline.' That could be light, with no people or stores; it could be fully loaded ie all tanks full and crew and stores, or it could be something like 'half load displacement' which is defined as 1 average sized person for each bunk, no stores, and all tankage half full. Most boat builders quote the lightest figure for displacement and leave the buyer to guess what the boat's capacity for stores etc etc really is. Fresh Breezes- Doug King I believe Doug is correct. |
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