Gaff-rigged cat boat with aft-mast and lateen sails! ‘Cat’ meaning the fore-mast is stepped at the bow. I love this boat! A ‘gaff’ is the spar at the top of the sail, holding it upright and out. On vessels with two or more masts, the aft-mast is called the “mizzen mast”.
Notice the ‘battens’ in the sail; strips of wood or plastic stays that keep the sails’ shape.
Photo taken on Kelly Lake; don’t know the persons or date. Perhaps someone has a clue… How peaceful the sailin’ scene. Roger
FYI, a lateen sail was an important design to navigation: See http://www.britannica.com/EBchecked/topic/331395/lateen-sail