The history.

Origins of the International Rule and the Metre Classes.

To appreciate the historical relevance of the Metre Classes,

one mus really look to the origins of yacht racing.

The Metre Classes are the oldest racing classes in the world,

still active.

They have survived a century of nautical evolution, politics

and economic recessions,

varying doses xenophobia and two world wars.

They have been chosen as Olympic and Americas Cup classes.

Quite a record.

The formula that enabled these classes to survive is kmown

as the International Rule.

The many attempts to enable differing yachts to race

competitively have always challenged yacht designers.

The first formulae where pretty basic; they relied on

boat length and sailarea. As design developed, other

measurements were introduced and now an array of

measurements (and indeed variations of these measurement

definitions) is used.

The origins of competitive sailing are pretty much a mixed bag.

While sail has been with us for centuries, sailing as a competitive    

sport is a relatively recent activity. 18th Century owners of           

fishing smacks, ferry operators, local pilot and revenue

(customs) cutters wanted faster craft and racing was

a natural extension.

Through this often extra-curricular activity, fishermen,

pilots, and revenue-officers (and their adversaries!)

pushed for speed and manoeuvrability.

As often the case, a sport emerged from commerce.

These developments occured on both sides of

the Atlantic; albeit in different ways. To understand

the interplay of America and Europe one has to

look at the caracters and motives of their welth

generators, the social circumstances of the times

and the passion for yacht racing caught the imaginationn

of an extra-ordinarily large

portion of the poupation.

The impetus in European sailing was largely driven by English

and Scottish commercial interests. Royalty and their associates

also played with sailing, albeit largely as spectator pastime.

The industrial revolution had created great wealth giving

a great part of the population more leisure time and more

money, to watch or to be involved in sailing.

The resultant wealth accumulation in the northern USA

from the American Civil War enabled industrialists to develop

their sailing pursuits.

Founding yacht clubs emerged in the 1830s,

one of the first being The Royal Yacht Squadron.

Originally founded in 1815 as The Yacht Club,

the qualification entitling a gentleman to become a

member was the ownership of a vessel not under 10 tons.

Today this is interpreted as a gentleman actively

interested in yachting. In 1820, when the

Prince Regent became George IV, Royal was added

to the name.

In 1826, the Club took organizing racing as a principal

feature of the annual regatta.

While the Cork Harbour Water Club was founded in 1720,

their activities were originally limited to sailing in various formations, following complicated signals and in general

copying naval engagements of the day – actual racing

was taken up later.

By the end of the nineteenth century yacht design

had become a crucial factor and the now famous

names such as Herreshoff, Dixon, Kemp, Ratsey,

Burgess, Fife and Nicholson appeared.

Several came with academic backgrounds,

introducing engineering fundamentals; others

produced revolutionary design concepts.

The period from the 1880´s to around1910

produced quite extraordinary yachting thinking

and many superb yachts.

The new wealthy industrialists were fascinated by

it all and with their financial input, the new specialist

builders were eager to take up build challenges.

We may be astonished by the costs of today’s

Americas Cup challenges; these are small

compared to the comparable spending of

Morgan, Vanderbuilt and Lipton. Include a few kings,

princes and magnates and you had a very heady mixture!

By the late 19th Century Great Britain,

France and the United States had individually

developed formulae that constrained either hull

dimensions, sail area or both. Eventually it was

recognized that any international rule would have

to take in account a combination of these factors

and in Januari 1906 the YRA (the forerunner of the ISAF) hosted a meeting in the Langham Hotel in London

where the concept of a new genareal rating rule was proposed.

The evolving nature of design and materials

had to be taken into account and for such a ruke to be effective, it had to be accepted universally.

While United States were reluctant to move from their Herreshoff or Universal Rule and France wanted amendments, all agreed to meet again later that

year in October in Berlin. At this second meeting

the finer points of The International Rule were

finalized and this committee (known as

the International Yacht Racing Union) met again in

October 1907 where the Rule was approved.

This remarkable document is the foundation of

yacht racing. It covers Measuring & Rating,

Scantling Regulations and Sailing Rules.

It acknowledges change is inevitable and provides

for these. It is in many senses liberal, yet ensures

the spirit of competitive sailing is retained.

While the International Rule covered some eleven

Classes, the 6, 8 and 12 Metre Classes have survived

and are actively racing today.

All three classes were used as Olympic Classes

during the first half of the 20th Century.

To date ther have been two Rule changes and the

Third Rule is relevant today. Each change reflected the progressive design thinking, developments in

materials and engineering progression.

It is a remarkable document.

Of the Classes, the 6 Metre has been the most

poular in build numbers.

This is mainly due to the cost, ease of transport

and crewing need. Being the smallest class they are

the cheapest to build and maintain.

Several were built to test new designs for the 12 Metres.

There are well over 1000 6 Metres in existence,

many from the likes of Olin Stephens, Pelle Petersson,

Ian Howlett, Fife, McGruer and Camper & Nicholson.

It is a tribute to the International Rule origins

that the 6 Metre Class yachts still race together.

Classic (those built before 1965) and Modern yachts

race together and many fast Classics give the

moderns a hard time!

The come about and the success of the 2,4mR Class

in the 20th and the 21st Century again proves how wisely

the International Rule is put together.

All that had to be done to make it useful for this

small size of yacht was an increase in draft to

make up for the loss of RM/volume when

downsizing this much.

Today there are about 400 2,4mR yachts

registered in the International 2,4mR Class

but many more has been built and are sailing

outside of the class.

Origin of the 2,4mR class

The Mini 12 concept surfaced in several places and forms

in the beginning of the eighties, most of them where attempts

to form one design small keelboats. In the UK it was

the Illusion the Shadow. In the US they had the Defender

on  west-coast and the Millimeter on the east-coast but it

was in Stockholm in Sweden that what we now know

as the International 2,4mR class, evolved.

Odd Linqvist, Håkan Södergren and Peter Norlin each

designed a small sailing yacht based on the classic Metre Rule.

They where called Minitwelves to mark the close relationship

with the famous Twelves then used in the Americas Cup.

The class soon grew popular as it offered a whole new

concept to sailing and many well known and famous sailors

joined the class. That the boats where very well suited for

disabled sailors gave the class an extra dimension and media

coverage, never before had there been a boat attractive to

such a wide specter of sailors.

By the end of the eighties the class was established and

in 1988 the first set of class rules was accepted by

the Scandinavian sailing Federation and in 1993 it was

acknowledged by the ISAF and granted status as

an international class.

The Rating Rule

Main characteristics.

This is the Rating Formulae that defines the 2,4mR.

Rating where;

L=the length according to the Class Rule D.6.3

d=the midship girth difference according to Class Rule D.6.4

F=the freeboard height according to Class Rule D.6.5

S=the total sail area according to Class Rule G.2.3

The Rating, R, and/or the factors in the formula shall be added with penalties, if any, according to Class Rule D.7. Calculations shall be carried out to the nearest millimeter.

The rating formula above is the same as for the 12mR Class and the 6mR Class and some other metre classes.

The difference is that R=12.00 and 6.00 respectively instead of 2,4.

Other dimensions for the 2,4mR Class are divided by 5 from the 12mR Class Rules or by 2,5 from the 6mR Class Rules.

However, the draft of the 2,4mR must be deeper than the proportion to the other classes, as the sailing qualities would suffer otherwise.

As the weight of the crew in a 2,4mR is propotionally higher than for a 12mR or a 6mR compared to the total displacement, the weight of the 2,4mR boat has been decreased by 35kg from the rating displacement.

The dimension L is the length of the boat in a plane 36mm above the waterline plane with the boat in  measurement condition, and added by the girth differences in the bow and stern.

The freeboard height shall not be taken as more than 292mm when calculating the rating value.

The penalties mentioned in D.7 are for draft exceeding 1000mm, for displacement below the minimum displacement, for beam smaller than 720mm, and for tumble home exceeding 15mm. The minimum displacement is calculated from the formulae (0,2xLWL + 0,06)3.

The sail area is the sum of the main sail triangle area and 85% of the fore triangle area. The main sail is calculated as the right angled triangle with the smaller sides P and E, where P is the length of the luff and E is the length of the boom. The fore triangle area is then calculated as the right angled triangle with the smaller sides I and J, where I is the forestay height and the J is the fore triangle base which is the distance from the front of the mast to the intersection of the forestay and the deck.