The designation of the C class is derived from the International Yacht Racing Union (IYRU) classes as devised at the founding of the IYRU itself. There are 4 development classes, A to D.
The A class has a strong following and many one design classes fall under this category such as the Unicorn. The Tornado used to fit into the international B class, however the class has developed outside the basic B class limitations. D class boats are rare and the use of D class designation has mainly been limited to sail area measurements for speed sailing craft.
C class has been the area where most development has taken place mainly due to the existence of the International C Class catamaran Championship. Since then, the IYRU has reformed into ISAF and the C Class was later dropped due to lack of interest. After that, the class took a life of its own and the story continued regardless.
Since the creation of the I4C, the class has been managed by the C Class Catamaran Association, headed by Steve Clark.
C Class Rules (as of December 3rd, 2003)
- A catamaran is defined as a two-hulled sailing boat with essentially duplicate or mirror image hulls, fixed in parallel positions.
- 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).
- 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.
- 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 and the crew shall be two people.
- The original C Class rules only permitted one trapeze per side. Only one crew member could use the trapeze at any time. In 2004 the C class association agreed to allow both crew to trapeze at future events.
- 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.