The International Seven 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. "Seven" in class name does not, somewhat confusingly, refer to length of the boat, but product of the formula; 7mR boats are, on average, 13 meters long.

History

The 7mR was used as an Olympic Class during the

1908 Events January * January 1 – The British ''Nimrod'' Expedition led by Ernest Shackleton sets sail from New Zealand on the ''Nimrod'' for Antarctica. * January 3 – A total solar eclipse is visible in the Pacific Ocean, and is the 46 ...

and

1920 Olympics The 1920 Summer Olympics (french: Jeux olympiques d'été de 1920; nl, Olympische Zomerspelen van 1920; german: Olympische Sommerspiele 1920), officially known as the Games of the VII Olympiad (french: Jeux de la VIIe olympiade; nl, Spelen van ...

. 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 200 boats were ever built.

Rule development

1907 Rule

Used from 1907–31.12.1917 :

7.000 \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. :

7.000 \mbox = \frac

where *

L

= waterline length (LWL) *

G

= chain girth *

d

= difference between girth and chain *

S

= sail area *

F

= freeboard

Olympic results

References

* {{Olympic class sailboats Keelboats Olympic sailing classes Development sailing classes