[PSUBS-MAILIST] Overpressure on dome

[Alan James via Personal_Submersibles]

  Hi all,need some group input here.I was looking at a picture of Snoopy's dome that Doug posted on Facebook. (below)The 6 dome retainers that are made of plastic were making me nervous.There have been a couple of cases of domes blowing off. I think  George Kitrigewas one of them. So I wanted a bit of analysis on this scenario in general.What sort of overpressure can you expect at a maximum on a dive?Doug's overpressure valve operates at .5psi but if you were 3psi overpressurethe valve wouldn't operate till you were 5ft from the surface & you would have a shorttime to get the pressure down. Also wave movement would factor in & fluctuate the pressure quickly at that depth.I think the K250 dome is 24" diameter. I calculated out that there would be 452lb pressure on the dome retainers for every 1psi overpressure. I based this on the area of a 24" disc, or should I be basing it on the area of the dome? (Sean)At 3psi that would be 226lb lifting force on each of those 6 plastic retainers!What is a good safety factor here? (Sorry for picking on Snoopy Alec)Cheers Alan


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