lbs. per sq. ft.

Discussion in 'Boatbuilding' started by guest200901, Jul 25, 2007.

  1. guest200901

    guest200901 Guest


    does anyone know the weight of the hull bottom to pounds per sq ft. ?
  2. Jeff
    Joined: Jun 2001
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    Jeff Moderator

    Of which hull? You have to give at least the size and type of boat and type of construction for anyone to be able to provide an answer.
  3. guest200901

    guest200901 Guest

    lbs. per sq. ft


    what i am tring to find out is how far 1 sq ft. will sink 1 sq. inch ,
    and how many lbs. it takes to sink 1 sq inch.......
  4. alan white
    Joined: Mar 2007
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    alan white Senior Member

    Volume sinks according to its shape, not its area. But that answer hardly makes sense either because your question is strange to begin with.
    Maybe you mean cubic feet, cubic inches.
    Try phrasing the question again in other ways. Forget about units of measurment and concentrate on what you need to know.
    For example, "What is the formula for determining how much deeper a boat sits in the water when a certain amount of weight is added to the displacement?"

  5. Palmer
    Joined: Nov 2002
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    Palmer Junior Member

    Pounds per inch of immersion is based on waterplane area, not hull surface area.
    For saltwater it's 5.33 lb/ft^2
  6. yipster
    Joined: Oct 2002
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    yipster designer

    metric, 1 kilogram equals 1 liter water, cant be easy'r
  7. alan white
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    alan white Senior Member

    Metric is easier, especially in this case. I am thinking you need to ask about sinking cubic, and not square inches. Sinking square inches would apply to waterplane, which changes on all but a straight-sided box shape with each inch of additional immersion. So waterplane is an area of so many square inches, which if pushed deeper into the water a certain distance allows a calculation of added volume immersed (and the waterplane generally changes somewhat as the boat goes deeper, so the formula is further complicated by the actual vertical shape of the hull-sides).
    The waterplane, therefore, is only meaningful as one of many waterplane slices all the way down to the bottom of the keel, each of which must be seperately calculated in order to know how much deeper the boat will sink from any given waterplane (waterline) to the next. Added up, all the waterplanes multiplied by all of the distances between them equal displacement, which is calculated at about 64 lbs per cubic foot of salt water, and about 62 lbs for fresh water.

    1 person likes this.
  8. guest200901

    guest200901 Guest


    o.k. ?

    let me ask the question this way please:

    if i have a sq. box 1` ft x 1` ft how much weight does it take to draft 1" inch ?

    thank you..............
  9. guest200901

    guest200901 Guest


    the draft calculation is for the flat side of the 1` ft square box.

    (forgot to write that info in the last post).

  10. KnottyBuoyz
    Joined: Jul 2006
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    KnottyBuoyz Provocateur & Raconteur

    1 cubic foot of water weighs approx. 62.5lbs. Divide that by 12 and you get approx. 5.2 lbs.
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