In a message dated 7/1/99 6:34:11 PM, rmorrisson@unidial.com writes: <<So, if you are designing implosion resistant coke bottles, add snug cardboard rings, if you are designing subs, make sure you have 100% continuous welds between rings (stiffeners) and the hull. Dick Morrisson >> I wonder what the crush depth of a coke bottle is? Vance