The Marblehead is another of the international classes.    The boats are either radio-controlled or free sailed using vane-controlled steering. The Class Rules are 'open', which means that anything is permitted provided it is not specifically prohibited by the rules.  This allows great freedom of design and construction within the main parameters that determine speed. These are a maximum length of 1290mm, draught 700mm, and 0.5161 sq metres of measured sail.    Ultimate efficiency and excellent performance has been developed within these simple limits.

Current hull designs are very narrow, with stability coming largely from the deep fins.    This has allowed post-1991 designs to remain competitive and to give very close racing.