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In searching thru my saved buoyancy data, I found this great data from Ray, I had saved several years ago, that might help us. -------------------------------------------------------------------------------- "Bouyancy Question: Why you are more buoyant in salt water then in fresh water? Answer: Displacement equals the amount of liquid an object displaces or moves out of the way when put into that liquid. The force of that displaced water pushing on a hull is called Bouyancy. If an object floats then the amount of liquid displaced weighs the same as the object and overall that object is less dense then the liquid it is floating on. Formulas: Bouyancy = volume of liquid displaced X density of liquid displaced (lb) (ft^3) (lb/ft^3) (also known as displacement) or shifted around: Bouyancy (lb) Displacement = ---------------------------------- (ft^3) density of liquid displaced (lb/ft^3) Constants: lb = pounds ft^3 = cubic feet Density of fresh water is: 62.3 lb/ft^3 Density of salt water is: 64.0 lb/ft^3 Example: A boat weights 100 lb. How much fresh water and salt water will it displace? Which liquid is more buoyant? Fresh Water Salt Water Bouyancy Bouyancy Displacement = ----------------- Displacement = ----------------- Density Density 100 lb 100 lb = ------------------ = ----------------- 62.3 lb/ft^3 64.0 lb/ft^3 = 1.61 ft^3 = 1.56 ft^3 Salt water is more buoyant since less is needed to displace the same weight." ( Ray Keefer 16 Jan 2001 ) Your resident pipe dreamer ;)' Regards, Szybowski From: bottomgun@mindspring.com To: personal_submersibles@psubs.org Subject: RE: [PSUBS-MAILIST] Upward Buoyant Pressures on Ambient Interior Surfaces Date: Thu, 4 Sep 2008 20:35:08 -0400 Another important thing to remember from basic physics is that a pressure is sensed throughout a fluid…even across a fluid interface. WE are talking about two different pressures here: a differential pressure that is negligible across the hull (or near non-existent…remember we are talking about ambient subs) and the buoyant force from the entrapped air. All of these forces are in equilibrium otherwise the air bubble would be constantly expanding or contracting. There will not be much change with breathing because as you breathe in decreasing the bubble, your lungs expand displacing the water.
You have to be careful with some diver’s pressure sensing watches as they depend on water contact to activate the depth feature.
Gotta pack, we are to be evacuated from the Base tomorrow afternoon by C-130 due to hurricane Ike bearing down on us. R/Jay
Respectfully, Jay K. Jeffries Andros Is., Bahamas
Talk sense to a fool and he calls you foolish. - Euripides (484 BC - 406 BC)
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