At the 2004 Summer Olympics in Athens, Blanckenberg qualified for his second South African team, as a 24-year-old lone sailor, in the Laser class by placing eighth and obtaining a berth from the 2003 ISAF World Championships in Cadiz, Spain. Unlike his previous Olympics, Blanckenberg could not compensate from an early surge in the opening to climb again on top of the rankings, as he finished seventeenth out of forty-two sailors in the official fleet with a net score of 156.