So.. now everyone knows why the vintage aluminum Roamers are still going strong... Tank metal.. bloody 5086 tank metal. Oh, and it is. Wiki says... "5086 is the preferred hull material for small aluminum boats or larger yachts. Its high strength and good corrosion resistance make it an excellent match for yachting." "5086 has been used in vehicle armor, notably in the M113 Armored Personnel Carrier and M2 Bradley Infantry fighting vehicle."