# lbs. per sq. ft.

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

1. ### guest200901Guest

hello...........!

does anyone know the weight of the hull bottom to pounds per sq ft. ?

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### JeffModerator

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. ### guest200901Guest

lbs. per sq. ft

hi.........,

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.......

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### alan whiteSenior 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?"

Alan

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### PalmerJunior Member

Pounds per inch of immersion is based on waterplane area, not hull surface area.
For saltwater it's 5.33 lb/ft^2

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### yipsterdesigner

metric, 1 kilogram equals 1 liter water, cant be easy'r

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### alan whiteSenior 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.

Alan

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8. ### guest200901Guest

displacement

o.k. ?

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

thank you..............

9. ### guest200901Guest

displacement

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

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

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### KnottyBuoyzProvocateur & 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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