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Anyone know how much weight a gallon of air will float?

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Anyone know how much weight a gallon of air will float?

Old 05-21-2007, 04:07 PM
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Mr. Mugen
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Default Anyone know how much weight a gallon of air will float?

I am helping a friend build a make/shift dock for summer at the cottage. Lake level dropped a bit but is expected to come back up. We need to build a simple floating dock. We have nearly 40 empty barrels of beer to use as floatation.

My question is how much weight will a gallon of air float? I know there is some kind of formula for this but am having trouble locating it. If you's could help me out here I will gladly accept it. Thanks, Kevin
Old 05-21-2007, 04:57 PM
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Default RE: Anyone know how much weight a gallon of air will float?

I'll take a stab, and say that at 70deg. F and standard atmospheric pressure of ~14.7psia, it will support about .00997lbs.

We'll see if I am correct.
Old 05-21-2007, 07:18 PM
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Default RE: Anyone know how much weight a gallon of air will float?

A gallon is 4 liters, so you will be displacing 4 liters of water if the barrel is fully submerged. 4L of water weighs 4kg so you will have 4kg of displacement, or 8.34 pounds. One gallon of air should be able to support a little less than 4kg if it is almost completely submerged, I dont think you want the barrels submerged past 3/4 or so when the dock is fully loaded.
Old 05-21-2007, 10:58 PM
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Default RE: Anyone know how much weight a gallon of air will float?

Well, I'd say that my numbers were a tad low....
Old 05-22-2007, 12:00 AM
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Default RE: Anyone know how much weight a gallon of air will float?

Yeah if pushed on a gallon of milk, it's probably supporting around 8-9lbs before it sinks.

Oh well Reiko. Again, just a tad off. lol
Old 05-22-2007, 09:09 PM
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Default RE: Anyone know how much weight a gallon of air will float?

Thanks guys. I had a feeling that is how it would turn out but thought I would ask instead of making a fool of myself. I am going to use the bathroom scale and a milk jug and the bath tub and see for sure. It's digital so a reflection should give me the reading. I'll let you's know what numbers show up.
Old 05-22-2007, 11:25 PM
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Default RE: Anyone know how much weight a gallon of air will float?

Call the Mythbusters
Old 05-23-2007, 06:34 AM
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Default RE: Anyone know how much weight a gallon of air will float?

Hands was right on. Water weighs about 8.33 pounds per gallon. Floatation =weight of water displaced by an object. Don't forget to subtract the weight of the empty container from the total gallon figure. say a 40 gallon drum weighs 40 lbs then 40x8=320-40=280 lbs of support or floatation.
Old 05-23-2007, 06:55 AM
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Default RE: Anyone know how much weight a gallon of air will float?

I was figuring the air density and not how it relates to flotation in water. Oops. I was only off by a factor of about 852. Hee.


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