It enables fair competition between boats that rate in the class whilst retaining the freedom to experiment with the details of their designs.

Though disparity between boats are minimized by the rule, enough variation exists so that races are as much about design and construction as they are about seamanship and tactics.

The Formula and associated rules for designing and constructing 12 Metre yachts has been modified several times from inception in racing.

If the rules were considered to be too loose then it would discourage the building of new 12 Metre yachts for fear of a new boat being outclassed even before it was launched.

The UK challenger was selected based on model tank testing and David Boyd's second design was chosen.

12 Metres continued to race together on a local basis but due to the high cost and without the impetus and prestige surrounding competition in the America's Cup, no new boats have been built since 1987 save one.

Also, a more prosperous global economy prevailed and the result was an increasing number of restorations and racing of older 'classic' 12 Metres.

For example, a yacht designed under the First International Rule would have a wooden mast, gaff rig, and sails made of cotton; whereas yachts designed under the Third International Rule, such as Vim, had a metal mast, Bermuda rig, and sails made from Dacron.