BELFAST, Maine — In the 19th century, adventurous Mainers signed up for years-long stints aboard whaling ships or sought passage aboard clipper ships headed to California during the Gold Rush. There were fortunes aplenty to be made out there, but there was a big obstacle, too: Cape Horn. The southernmost tip of South America, where the Atlantic and the Pacific oceans meet, was infamous for its strong winds and currents, giant rogue waves and icebergs.