I agree that pressure will be released from your hatch long before it would explode. The hatch cover will lift and burp.tx river rat said:<SNIP> Let me explain what I am saying, internal pressure is easier to contain with less strength.
Simple test take a milk jug fill it with water no problem. take that same jug empty it and submerge it in water
the jug will collapse. same amount of structure just different pressures. I use to build a lot of diesel storage tanks ,even a
500 gallon held several thousand lbs of fuel but if you forgot to open the vent just ounces of vacuum would fold it up like a paper cup.
My point is a sealed compartment with our hatch system will never fracture the hull, pressure will be released long before that ,and your boat will take more pressure from inside than it will externally.
Your examples of Diesel tanks and milk bottles aren't applicable, but interesting. Their skins serve as a membrane to contain a fluid. The skin is under tension and trying to tear apart. If over pressurized they would rupture in a tear - the skin would separate under tension. Think of a penny balloon. Yes, a thin skin can hold fluids, but it isn't pertinent to boat hull design. Just more smoke screen.
Our boats, on the other hand are the exact opposite. They are withstanding pressure from the outside with a rigid skin that maintains its structural rigidity; the skin is in compression. If they rupture, it would be from a puncture. The skin would first be compressed beyond it's capacity to maintain integrity, and only then would it separate and tear.
Chuck, given enough gritz, these principles of physics work even for simple southern folks.