Gogarty wrote:
I have been doing a lot of Googling but I can;t find an answer.

You have no doubt noticed that the sails on the current crop of
America's Cup challengers are not triangular -- even with a huge roach
-- but trapezoidal. How do they maintain that shape at the head? Is
there a gaff at the head parallel to the boom? How do they keep the
head of the sail from falling way off to leward? Is there some
arrangment of masthead sheets that keep the head parallel to the boom?

The headboard must consist of struts which form a triangle sewn into the
sail. although how this arrangement can stand up to the sheet/leech tension
is beyhond me.