metreclass

Metre class refers to a family of sailing yacht classes defined by the International Rule, a rating system developed in the early 20th century to enable fair competition among yachts of different designs. The name arises from the rule’s rating, which is expressed in metres rather than the boat’s actual length. Classes are designated by metre ratings, most notably 6mR, 8mR, 10mR, 12mR, and so on.

Boats in a metre class are designed to meet a specific rating according to a formula that combines various measurements, including aspects of hull form such as length on the waterline, beam, and girths, as well as sail area and other factors. Designers optimize hull shape, rigging, and ballast within the constraints of the rule to achieve the target rating while pursuing speed and seaworthiness. Because the rating considers multiple dimensions, metre-class yachts can vary substantially in appearance even when sharing the same metre designation.

Historically, metre classes gained prominence in the early to mid-20th century, with the 12mR class becoming especially famous for its use in the America's Cup from 1958 to 1987. The rule produced a range of elegant and diverse designs, from slender racers to more robust cruiser-racers, all categorized by the same rating concept.

Today, metre classes are largely of historical and classic sailing interest. They continue in vintage regattas and specialist fleets in various regions, and some ships from old metre classes remain actively sailed. In contemporary professional sailing, metre-class designs are less common, but the term remains relevant for discussions of yacht design history and classic racing.

---