The International Nine Metre Class is a construction class, meaning that the boats are not identical but are all designed to meet specific measurement formula, in this case International Rule. At their heyday, Metre Classes were the most important group of international yacht racing classes, and they are still actively raced around the world. "Nine" in class name does not, somewhat confusingly, refer to length of the boat, but product of the formula; 9mR boats are, on average, 18 meters long.

History

The 9mR was used as an Olympic Class during the 1920 Olympics

Sailing at the 1920 Summer Olympics

The sailing at the 1920 Summer Olympics consisted of a total of 16 sailing classes . Two of these classes finally did not have entries. For each class three races were scheduled from 7 July 1920 to 9 July 1920 of the coast of Ostend North Sea. On 10 July 1920 sail-off races could be held.Two...

. No entries were made.
The International Rule was set up in 1907 to replace earlier, simpler handicap system which were often local or at best, national, and often also fairly simple, producing extreme boats which were fast but lightly constructed and impractical. The rule changes several times in history. About 50 boats were ever build.

1907 Rule

Used from 1907–1920
where

• = waterline length (LWL)
• = beam
• = chain girth
• = difference between girth and chain
• = sail area
• = freeboard

Olympic results

No competitors did enter the Olympics in the 9 Metre.