text:  In 1961 , three Charles F. Adams @-@ class destroyers were purchased from the United States to replace the ageing Q @-@ class destroyers . Traditionally , the RAN had purchased designs based on those of the Royal Navy and the purchase of American destroyers was significant . HMAS Perth and HMAS Hobart joined the fleet in 1965 , followed by HMAS Brisbane in 1967 . Other projects included the construction of six River @-@ class frigates , the conversion of the aircraft carrier HMAS Melbourne to an anti @-@ submarine role , the acquisition of ten Wessex helicopters , and the purchase of six Oberon @-@ class submarines . 
  