Posted by Wayne on September 08, 2002 at 09:51:42:
In Reply to: Re: displacement is displacement posted by Eins on September 08, 2002 at 09:04:54:
What I was trying to say is that the small bubbles of gas are encased in the rubber as cells. The structure of the cell walls has some amount of rigidity and this prevents the gas from being affected as they would in an unrestrained fashion. If the bubbles were in a perfectly flexible media, they would be free to act as Boyle predicts.
The very nature of a material such as closed-cell neoprene causes the structure to resist the crushing forces of pressure. In this way the structure actually reduces the pressure exerted on the gas (like putting presure on an intact egg shell does not directly apply pressure to the contents). It is like taking a sealed semirigid container to depth.
That is why I was suggesting that it does not work to try to seperate the neoprene wetsuit material into its components for prediction of buoyancy. If you could truly seperate the gas from the solids, it would work. But the material has the held gas in cells and the rubber is acting like an intricate web of support structure.
The smaller and more crowded the bubbles are, the better the structure will resist allowing the water pressure to directly squeeze the gas. I think this is why the different brands of wetsuit material had such differing amounts of compression in the demo gizmo at the scuba show.
Wayne