12-metre class

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The 12-metre class is a group of sailing vessels which, while not identical, are all designed to a particular formula, so as to make the boats involved in a competition roughly comparable, while still giving individuals the freedom to experiment with the details of their designs. They are best known for their use as the vessels used for many years to compete for the America's Cup.

Rough equality between boats is ensured by requiring compliance with a formula that takes into account the length at the waterline, the girth (the measurement around the boat from one sideboard, under the keel and then back over the top on the opposite side back to the original side) and the sail area. The very carefully specified measurements are then entered into the formula, and the result must be 12 metres - hence the name of the class. Designers are free to change any of these variables (as well as other details, such as the size of the rudder and keel, etc), with the understanding that for any change in any of the measured attributes, something else will have to be adjusted, in order to make the formula produce the required value.

The "12-metre" in the class name thus has nothing to do with the actual length of the boats, which ranged from 65 to 75 feet (about 20 to 23 m) overall. They were all sloop-rigged, with their masts typically being about 85 feet (26 m) tall.

1 The Formula
2 America's Cup
3 Famous 12-metre Yachts
4 External links

[edit] The Formula

The following is the mathematical formula by which all 12 Metre yachts are measured that have been constructed since 1958 (International Twelve Metre Association):

<math>

12 \mbox{ metres} = \frac{L + 2d + \sqrt{S} - F}{2.37} </math>

where

<math>L</math> = waterline length (LWL)
<math>d</math> = difference between girth and chain
<math>S</math> = sail area
<math>F</math> = freeboard

[edit] America's Cup

When America's Cup racing resumed in 1958 after World War II, more economical vessels were desired to replace the huge and expensive J-class yachts that were raced in the 1930s; the 12-metre class was selected. In 1987, use of the 12-metre class was ended, switching to International America's Cup Class boats for the 1992 competition.

[edit] Famous 12-metre Yachts

[edit] External links

List of ISAF international keelboat classes
11 mR \| 12 mR \| 2.4 mR \| 5.5 mR \| 6 mR \| 8 mR \| Access 2.3 \| Dragon \| Etchells \| Flying Fifteen \| H-boat \| J/22 \| J/24 \| Melges 24 \| Open 60 Monohull \| Soling \| Star \| Tempest \| Yngling

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