In one embodiment, {HEAD ~ a single double wall} is formed in {TAIL ~ both the top and bottom plies} 
In one embodiment , { HEAD ~ a single double wall } is formed in { TAIL ~ both the top and bottom plies }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL