The mandrel may be any suitable rigid, light weight material, but {TAIL ~ a foamed material} such as {HEAD ~ a structural foam} is thought to be most suitable 
The mandrel may be any suitable rigid , light weight material , but { TAIL ~ a foamed material } such as { HEAD ~ a structural foam } is thought to be most suitable
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH