Came across this figured I would share the sailing scene from the Thomas Crown Affair
http://www.youtube.com/watch?v=JVXoqy2Bo0Q
I also found this about the boats....but I dont know it indicates they sailed these on the barnaget bay. Being a sailor on the bay I know that in or outside of the 100 ft wide channel it is dicey to say the least, monohulls have a hard time that draw 4 or 5 ft, so I don't know about racing around with those big daggerboards
http://www.imdb.com/title/tt0155267/trivia
The catamaran that Thomas Crown is seen racing in Long Island Sound is a D-Type Catamaran. The earliest Class D catamarans were designed and built by individual amateur designers as early as 1963. Richard Karcher, Watchung, NJ built either USD#1 or #2 at the time. His "D" boats were sailed on Barnegat Bay in New Jersey for several years on an experimental basis. Richard also designed and manufactured several other types limited production catamarans at the time, one of which was considered as the official Olympic Class Catamaran and participated in the trial in England. Due to the vast amount of power that this design represented, no "production" versions were ever produced and interest and research into this Class waned. Years later in the 1980s interest in this extremely fast and highly unstable yacht design was revived by California based aeronautical engineers who tried to break inshore multi-hull speed records. Today there are only a handful of them left in the world.
Maybe they were experimenting ripping off the boards and rudders??