lbs per sq. ft.

Discussion in 'Boatbuilding' started by zptaiopdhnfcre, Feb 11, 2012.

  1. zptaiopdhnfcre
    Joined: Feb 2012
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    zptaiopdhnfcre Junior Member

    i once knew this question;

    how many lbs. does it take to sink 1 sq. ft. 1 inch ?

    thank you !
     
  2. dougfrolich
    Joined: Nov 2002
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    dougfrolich Senior Member

    Sink it into what?

    If you take an ave. seawater density of 64lbs./ft^3 then it would take 5.33 lbs.
     
  3. zptaiopdhnfcre
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    zptaiopdhnfcre Junior Member

    whoops............!

    sorry !
    i take it it must be a different number# of calculation for fresh water and salt water ?
    are the numbers of lbs. different ?
     
  4. troy2000
    Joined: Nov 2009
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    troy2000 Senior Member

    Yes. Salt water is denser, so it takes more weight to displace it. Whether that's significant or not depends a lot on what you're playing with... you may not even notice it with a canoe, for example. But a cargo ship has separate Plimsoll lines to indicate its maximum load capacity in fresh water and seawater, among other variables.
     
  5. Frosty

    Frosty Previous Member

    What is the question, how much to sink a sq inch or a sq foot?

    If you once knew the answer you would think you would know the question.
     
  6. DCockey
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    DCockey Senior Member

    Archimedes principle. Buoyancy of a floating object equals the weight of the volume of water displaced. A volume of 1 sqare foot x 1 inch is 1/12 of a cubic foot. Sea water weighs approximately 64 lbs per cubic foot. Fresh water weighs approximately 62.4 lbs per cubic foot.
     
  7. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    when will the Americans learn that metric is the way that makes the world tick...?

    What is simpler than 1 liter of water = 1 kilogram. One cubic metre (1000 lt) = 1000kg;) For decimals - just move the point.
     
  8. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    Our foreheads are thick and our brains are small...maybe we'll catch on by the time we step foot on Mars.
     
  9. rberrey
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    rberrey Senior Member

    It,s like a railroad track and a Roman road , if it,s not broke dont fix it.
     
  10. DCockey
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    DCockey Senior Member

    Only if fresh water. Density of salt water is not a nice, round number in the metric system.
     
  11. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    Salt water: SG = 1025kg per cubic meter

    1 liter = 1.025kg and one cubic meter (1000lt) = 1025kg
    Because meter cube it is a thousand liter units (three zeros), the decimal get moved 3 places, simple as that...;)
     
  12. tinhorn
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    tinhorn Senior Member

    Now you're just showing off.
     
  13. zptaiopdhnfcre
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    zptaiopdhnfcre Junior Member

    thanks

    hey thanks for all the info !
    you people really try to help.

    thanks.
     
  14. SheetWise
    Joined: Jul 2004
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    SheetWise All Beach -- No Water.

    Well ... I believe it was Jimmy Carter who mandated the conversion ... and we did actually see some providers of petrol convert to liters ... but that was just to disguise price changes ...

    You're right of course. We're very obstinate. On the other hand, we're also very talented ... we can use both ;)
     

  15. zptaiopdhnfcre
    Joined: Feb 2012
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    zptaiopdhnfcre Junior Member

    does anyone need a fiberglass laminator or a mold maker ?
     
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