International Marblehead

The International Marblehead is a class of radio controlled sailing yacht used for competitive racing. It is a measurement controlled class administered by the International Radio Sailing Association. 
As a designated International IRSA class it is entitled to hold World Championships officially recognised by the International Sailing Federation. A Marblehead has a maximum length of 1290 mm and a maximum draught of ca 700 mm, but no minimum displacement. Up to six rigs are allowed, the tallest being about 2200 mm.