1 A catamaran is defined as a two-hulled sailing boat with essentially duplicate or mirror image hulls, fixed in parallel positions.
2 Sail area shall not be more than 27.868 square meters (300 square feet) Sail area to be measured in accordance with the “ISAF Measurement & Calculation of Sail Area Instructions” (Last issued May 1985).
3 The overall length of the catamaran shall not be more than 7.62 meters (25 feet). The length shall be measured between perpendiculars to the extremities of the hulls with the catamaran in her normal trim. The measurement shall be taken parallel to the centre line of the craft and shall exclude rudder hangings. However, if the athwartships width of a rudder within 153mm (6 inches) of the bottom of the hull is more than 76mm (3 inches), the length shall be taken to the aftermost point of the rudder.
4 The extreme beam shall not be more than: 4.267 meters (14 feet). The beam shall be measured at right angles to the centre line of the craft at the widest point and including all fixed or adjustable apparatus with the exception of a normally accepted trapeze or retractable seat.
5 The crew shall be two people.
6 There is NO rule 6.
7 The C class emblem shall be carried on the mainsail and shall consist of the letter C over two parallel horizontal lines over national letters and sail numbers. Sail numbers shall be allotted by the National Authority or Class Association appointed by the National Authority. The class emblem, national letters and distinguishing numbers shall be placed as prescribed in the Yacht Racing Rules.
Measurement Guide and Interpretations
1 Boat is to be measured assuming the design waterline or datum line is horizontal. Measurements are made parallel to or perpendicular to the centerline of the platform.
2 Length does not include rudder fittings, but if the rudder fittings have a measurable hydrodynamic or hydrostatic effect on the hull they shall be included in the length.
3 Daggerboards must be within the total beam in all positions.
4 Rudders must be within the maximum beam when centered.
5 The sail plan shall be within the maximum beam and length when the boat is floating level and the wing in “head the wind” position.
6 Wing measurement: Surfaces within 7 degrees of horizontal shall not contribute to sail area.
7 Wing Measurement: Surfaces that are separated by a slot shall be measured independently. Surfaces with integral flaps shall be measured as one surface.
8 Wing Measurement: If an element or surface changes size for any reason, the element will be measured in its largest configuration.
9 Trailing edge surfaces 90degrees to centerline are not measured as sail area.
10 The crew shall have at least one foot on the platform at all times when trapezing or using a sliding seat.