Hugh,I was thinking absolute pressure, not gauge. So I'm in agreement with you, I would set it as low as possible. I don't see any advantage to 3psig over 2psig, nor 2psig over 1psig, except if the smaller valued valves are not readily available.
The mounting of a large viewport could definitely be an issue depending upon its configuration, but a Grade(1) 1/4 inch bolt has more than adequate holding power for a 15psi cabin overpressure on a 36 inch hatch/viewport. If the diameter is less than 1/4 (6mm?), then yeah I see your concern with the fasteners as well.
Jon Hugh Fulton wrote:
Jon, I would be surprised if the pressure was as high as 15 psi. Vance guessed at 2 or 3 psi. I would think that 5 psi would be acceptable and that the 15 psi mentioned is so that people could not get into a decompression scenario as was mentioned earlier. 15 psi is a fair internal pressure to seal viewports against and even more of a concern if you were to be at 15 psi and then equalized the sub too quickly causing ear problems. Some of those big domed windows were held on with straps which did not seem to have very big threads on their fastenings form memory. Maybe Vance can rack his memory cells again. Hugh
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