[PSUBS-MAILIST] Dive report: Snoopy at Seneca

[Jon Wallace via Personal_Submersibles]

I've done some initial calcs and it looks to me that a LARGE air gap at 
sea level and a sharp bending trap is necessary to maintain a 
sustainable gap at depth.  For .25 inch ID tubing, an 18 inch linear air 
space gap (or trap if you think of it like a house sink drain) at 
sea-level would be compressed to about 1.8 inches of air gap at 350 
feet.  The deeper you go, the more tube required to maintain a 
reasonable air gap at depth.

Here are my calcs for 1/4 inch ID plastic tubing...

Ps = Sea Level pressure in ATM = 1
Pd = Pressure at 350 feet seawater in ATM = 10.74
Vs = Air gap volume at sea level = .125*.125 * pi * 18
Vd = Air gap volume at 350 feet = Vs * ( Ps / Pd)

Vs = .883
Vd = .0822

Air Gap = 1.8 inches in length at 350 feet