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Coast Guard Course?

Discussion in 'General Yachting Discussion' started by Beau, Feb 20, 2019.

  1. Capt J

    Capt J Senior Member

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    Which is exactly what I said in laymens terms. I'm a bit confused on how your statement contradicts my statement, unless you just couldn't resist the need for an early morning jab with no basis? You basically said the sameexact thing, you can weigh the ship and divide by the density of water to calculate the displacement .

    "Volume of Displaced Water = Weight of Vessel divided by the Density of Water

    Given any of the two variables above, you can solve for the third. " Pacblue


    I do a lot more in this industry than just drive yachts.

    My initial statement:
    "Displacement is measured in volume of water a ship displaced, in order to get (derive) the weight of the ship. Obviously nowadays, they can weigh the ship. By weighing the ship you can work backwards and get the displacement value."

    Work Backwards= is laymens terms for calculate, if reading comprehension is not your strong suit. And since the density of water (either fresh or salt, you choose) is a constant, you can calculate the displacement with just the weight and choosing what type of water the ship is displacing to get both the displacement values in freshwater and saltwater.
  2. Oscarvan

    Oscarvan Senior Member

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    So what about "registered tons?" Is that the weight of the ship?

    (Ducks for cover with large bag o' popcorn :D )
  3. Beau

    Beau Senior Member

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    Teach me. I always thought the weight of the displaced water could be different than the weight of the ship, but depending on that relationship it would ride higher or lower? or am I just missing the whole thing? I just hi jacked my own thread??
  4. Capt J

    Capt J Senior Member

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  5. Beau

    Beau Senior Member

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  6. gr8trn

    gr8trn Senior Member

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    I gained knowledge from NauticEd online.
  7. PacBlue

    PacBlue Senior Member

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    You stated "Displacement is the amount of water that is displaced measured in volume, not weight."

    When is the last time you saw displacement in volume units and not weight, as in the displacement of my boat is 70,000 lbs. not hey, the displacement of my boat is 1094 cubic feet?

    Why did you state that it is "not weight"? It has an absolute direct expression in weight, as the useful value to the laymen for displacement is expressed in weight - pounds, kilograms, long tons, or metric tonnes.
  8. Capt J

    Capt J Senior Member

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    Yes, displacement is the amount of water that is displaced by the vessel measured in volume, which you then multiply by the density of the water to get the displacement weight of the vessel.
  9. Capt Cole

    Capt Cole Member

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    I wish I had read your post before I replied to the OP. That was 180 seconds of my life wasted as I naively tried to offer support and encouragement for what I took as a sincere question. My mistake, won't happen again.;)
  10. Beau

    Beau Senior Member

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    NO! No ! NO! I think he was responding to me. His Reponses are not typical of this site. There are so many gals/guys who know "stuff" here, that you have to over look the inventive when it occurs (me). This is a very collaborative site filled with great people
  11. Capt Ralph

    Capt Ralph Senior Member

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    Guys, I know my attempted injection of crappy humor has some times failed. However, this tread has turned into another urine broadcasting contest. Lets get back to the OP.
  12. Beau

    Beau Senior Member

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    YEAH!
  13. Capt Cole

    Capt Cole Member

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    I agree. I have picked up some great info from this site. :)
  14. CaptPKilbride

    CaptPKilbride Senior Member

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    Ummm, no.

    Displacement is defined as, "The weight of water displaced by a floating object. Displacement is equal to the weight of the floating object"
    https://mdnautical.com/cornell-mari...-trim-for-the-ship-s-officer-4th-edition.html


    The volume of the water is a function of the specific gravity of the water the object is floating in. To simplify things, often a "constant" is used for freshwater versus saltwater, though the actual volume of water displaced will vary.
  15. Beau

    Beau Senior Member

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    Does a floating boat "displace" more weight of water than its displacement? If they are equal is it floating at its gunwales rather than water line?
  16. PacBlue

    PacBlue Senior Member

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    Good question, this is similar to what tripped the CG Auxiliary guys.

    A Naval Architect has a design waterline clearly marked on the lines plan which portrays the shape/geometry of the hull. This design waterline is to account for all the structure, machinery, tanks, goods and owners gear and equipment. That design waterline is where we want to float the boat at the desired weight that was carefully calculated to account for normal operating conditions. If we did a good job, they match precisely and everyone walks away happy.

    So a floating boat should displace the weight of water as close to the prescribed design waterline volume as possible. At full load it will sit slightly deeper, at light load slightly higher, but we are usually talking a few inches, +/-.

    If it is floating at its gunwales, it has been overloaded by some circumstance and is heavier than the design waterline displacement, and if it gets overloaded enough, it will sink lower and finally run out of reserve displacement and sink below the surface.
  17. CaptPKilbride

    CaptPKilbride Senior Member

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    All things find an equilibrium. In this case, the weight of a floating boat exerts a downward force. There is a counteracting buoyant force provided by the volume of the boat. Where it floats is a function of how much the boat weighs (displacement) versus how much volume is immersed.