Denmark:
København, it was the world's largest sailing ship at the time, and primarily served for sail training of young cadets. It disappeared without a trace in route from Argentina to Australia on Dec 22nd 1928.
On September 21, 1928, the København departed from Nørresundby in Vendsyssel for Buenos Aires on its tenth, and ultimately final, voyage. The captain was Hans Andersen; 75 persons were aboard, including 26 crew and 45 cadets. The goal was to unload a shipload of chalk and bagged cement in Buenos Aires, take on another load of cargo and sail for Melbourne, and then bring a shipment of Australian wheat back to Europe.
The København arrived at Buenos Aires on November 17, 1928, impressing the locals, in particular emigrant Danes. The cargo was unloaded; however, the departure was delayed as there were no paying commissions to take the cargo to Australia. Finally, on December 14, Captain Andersen decided to ship out to Australia without a cargo. The voyage was expected to take 45 days. On December 22 the København exchanged radio messages with the Norwegian steamer William Blumer, indicating they were about 900 miles from Tristan da Cunha and that "all is well". The Blumer attempted to contact the København again later that night, but received no response. The ship was never heard from again.
She was officially announced "missing" by Lloyd's of London on 1 January 1930.
In 1934 The New York Times reported that a København cadet's diary had been found in a bottle on Bouvet Island in the South Atlantic. The supposed diary indicated that the ship had been destroyed by icebergs and abandoned, the crew taking their chances in lifeboats. In 1935, human remains and the remains of a lifeboat were found partly buried in the sand along the southwest coast of Africa. These may have come from København
https://en.wikipedia.org/wiki/København_(ship)
