With any racing yacht, the largest contributor to variable costs are the sails. A boat with newer sails will almost always have a greater speed potential than a boat with older sails of the same design. To keep costs low and ensure that each boat is racing with the most equal sails possible, the IOD class has evolved a very specific sail purchase program that is required to be implemented by each local fleet. The Class encourages each local fleet to develop sails for their boats that suit the specific characteristics of their local sailing area.