Forces on an underwater vessel

[yellowcouch]

I have a question about a Fiberglass Hemisphere that is 16" in diameter and 8 " in height. It is being used as a vessel under the water so it has a closed top. I wanted to know how to figure out how much stress from water pressure it will handle before it fails.
thanks!

 

[haruspex]

Which way up is it? Are you saying it has a flat top, or a (possibly open) flat base?

 

[Low-Q]

I understand it this way that you have a kind of bucket upside down. The water pressure will compress the air inside, at the same time as the surrounding pressure (outside the vessel) is the same. The vessel will be filled with water as the air is compressed to a smaller volume. The vessel will probably not "blow apart" under such experiment unless the vessel is so tall that there is considerably less water pressure at the top compared to the bottom. The air inside will have approx the same pressure acting on the walls any place inside. Considerably higher on the top compared to the water pressure outside - too much difference and it will blow apart.

Vidar