The International Ten 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. "Ten" in class name does not, somewhat confusingly, refer to length of the boat, but product of the formula; 10mR boats are, on average, 16.5 meters long.

History

The 10mR was used as an Olympic Class during the 1912 and 1920 Olympics. 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 20 boats were built.

Rule development

1907 Rule

Used from 1907–1920 thumb :

10.000 \mbox = \frac

where *

L

= waterline length (LWL) *

B

= beam *

G

= chain girth *

d

= difference between girth and chain *

S

= sail area *

F

= freeboard

1919 Rule

Used from 1920–1933 thumb :

10.000 \mbox = \frac