International A Class
The International A Class is one of the oldest and most distinctive classes in radio sailing. Large, powerful and graceful, A Class yachts have an unmistakable presence on the water and a fleet racing together remains one of the most impressive sights in the sport.
Unlike a conventional box-rule class, A Class yachts are not restricted to a fixed overall length. Instead, the class is controlled by a rating formula that balances waterline length, displacement and sail area. Under the formula, the permitted sail area reduces as displacement decreases and as waterline length increases. This creates a fascinating design balance and allows considerably different yacht designs to compete within the same class rule.
The origins of the rating formula date back to 1922, when it was devised by Major Malden Heckstall-Smith, then editor of Yachting Monthly, as a means of testing an alternative to the International Linear Rating Rule. The principles behind this approach have endured for more than a century, with similar elements of the Linear Rule continuing to be found in the rating formula used by the full-size 5.5 Metre Class.
Traditionally, A Class yachts have tended towards relatively heavy displacement designs, giving them excellent momentum, stability and a particularly graceful sailing characteristic. The rating rule, however, provides considerable design freedom and also permits lighter hull forms, which can offer impressive performance as the wind strength increases. This flexibility has resulted in a wide variety of hull shapes and design philosophies throughout the long history of the class.
Modern A Class yachts make extensive use of carbon fibre and advanced composite construction, particularly for hulls, foils and spars. Despite the use of modern materials and construction techniques, the fundamental principles of the class remain firmly connected to its long heritage of yacht design and development.
Their substantial size, long hulls and generous sail plans give A Class yachts a commanding appearance both ashore and on the water. Their combination of momentum, stability and efficiency produces a distinctive style of racing, while the freedom provided by the rating rule continues to offer considerable scope for designers and builders.
In recognition of its history and enduring importance to international radio sailing, the International A Class was granted Classic Class status in 2004. The designation recognises the class's heritage and its special place within the sport while allowing it to continue developing within its established rating principles.
More than a century after the origins of its rating rule, the International A Class continues to combine traditional yacht design principles, modern construction and impressive performance, preserving one of radio sailing's great development classes for future generations.