International rule (sailing)

Due to the difficulty with accurately measuring the internal volume of a sailing vessel with a hull of varying curvature, a set of distances at points on the hull was defined to be measured and entered into a formula which then defined the tonnage and hence the taxes to be paid to the government of the day.

The adoption of the British Thames Measurement by the Yacht Club of France in 1870 may mark the beginning of international rating rules.

By the early 20th Century yacht racing had spread across Europe but each country had its own different rating rules but they all typically used similar principles.

International competition was always subject to various forms of handicapping which was often subjective and certainly open to protest What was needed was a common rating or an agreed International rule, which would enable yachts from one country to race competitively in a different country.

Representatives from eleven countries attended, together with an observer from the United States, plus several respected nautical engineers and designers and they started to formulate the International rule.

The Rule created a formula that took into account most problematic areas that had previously caused dissent among the racing nations.

Used from 1907 to 1920 where Used from 1920 to 1933. where Used from 1933 to 1939. where It is important to note the term Metre does not refer to the length of the yacht; it is the product of a formula and denotes the class.

It is commonly believed that the term Metre refers to the units of measurement used for the input values entered into the formula.

The relation between the length and area components of the formula are preserved whether in metric or imperial units.

For the International rule, the rating number is approximately equal to the sailing length of the hull.

[2] The first rating rules were first expressed as the weighted sum of various speed factors such as length and sail area.

It was the illustrious architect, Dixon Kemp, who began the tradition of expressing British rules as trivial fractions with a divisor of "2", thus starting the tradition of the age old question: "Since your boat is a Six metre, why is it 12 metres long?"

Designed by Norwegian Bjarne Aas, and modeled after his classic 6 metre Saga, the International One Design sloop, or IOD, is today raced in fleets based in Norway, Sweden, the UK, Canada, Bermuda and the United States of America.

As a keelboat, and unlike a dinghy, it does not require the crew to balance his weight to keep the boat from capsizing.

Partly this is a result of the fact that the R-metre boats had to adhere to Lloyd's strict scantling rules, that has given them longevity that very few other traditional classes have been blessed with.