I have noticed what appears to be a geometric theory of pressure vessels. Its probably already been proved, so has anyone heard of it? If not, I may play around to see if I can get any math out of it to work. I have noticed that if you have any closed body with internal pressure, and you make a cut anywhere along the body, and separate the body so that its a new free body diagram, that the net force in the direction perpendicular to the cut, is always going to be equal to the pressure, times the cross sectional area where the cut was made. Its simliar to the Gauss' law about net flux in a way, except that the magnitude of the electric field goes down in Gauss' law, here the pressure force always is the same, even at the cut. Thanks guyz!