dBoats in International A Class are not limited in length, but are controlled by a formula which balances waterline length, displacement, and sail area. Using this formula, sail area reduces as displacement reduces and as waterline length increases. The formula was devised in 1922 by Major Malden Heckstall-Smith, then editor of the Yachting Monthly, for testing an alternative to the International Linear rule. A similar rating rule is still in use today in the 5.5 Metre class rule which also uses elements of the Linear rule. Although A Class boats are of a heavy ‘type’ there is flexibility to create lighter hull forms which excel in brisker conditions. aNevertheless they are big boats compared with other rc classes and a fleet of A Class boats is an impressive sight. A modern A Class will usually be made using carbon fibre - hull, foils and spars.