# lbs per sq. ft.

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

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### zptaiopdhnfcreJunior Member

i once knew this question;

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

thank you !

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### dougfrolichSenior Member

Sink it into what?

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

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### zptaiopdhnfcreJunior 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 ?

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### troy2000Senior 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. ### FrostyPrevious 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.

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### DCockeySenior 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.

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### Wynand NRetired 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.

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### lewisboatsObsessed Member

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

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### rberreySenior Member

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

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### DCockeySenior Member

Only if fresh water. Density of salt water is not a nice, round number in the metric system.

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### Wynand NRetired 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...

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### tinhornSenior Member

Now you're just showing off.

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### zptaiopdhnfcreJunior Member

thanks

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

thanks.

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### SheetWiseAll 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

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### zptaiopdhnfcreJunior Member

does anyone need a fiberglass laminator or a mold maker ?

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