A large foresail used in racing and cruising yachts. Its features are (a) its size, considerably larger than a standard jib and often larger than the mainsail, and (b) its shape, with the clew extended much farther aft than in an ordinary jib, overlapping the mainsail by an appreciable amount, its foot often parallel with the deck sheer. In effect, it combines jib and staysail in a large single sail. As well as transferring the main driving power of a yacht's sails to the fore-triangle, it also, by the sheeting of its clew well aft of the mast, increases the speed of the airflow over the luff of the mainsail. This increases the partial vacuum there which helps to pull the yacht forward. See aerodynamics for an analysis of this forward pull.
Subjects: Maritime History.