IRSA A Class

dBoats in IRSA 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.

The class was given Classic Class status in 2004. For full information concerning what this means please see the IRSA Regulations.

A Class documents (click to expand categories)

IRSA Ten Rater Class

P1030880Boats in the IRSA Ten Rater (10R) class are not limited in length by the class rules and usually have overhangs extending beyond their waterline endings. They are generally light, narrow, stable, seaworthy and fast. This IRSA international rule is based on the 1887 “length and sail area rating rule” which allows shorter waterline length boats to have higher sail areas, while longer LWL boats have smaller sails. It is an ‘open’ rule with great freedom to develop design and construction, particularly in rigs and sail plans. Many different hull forms can be found in the 10R class. lenzerheide 10r_e_m_096A modern 10R will usually be made almost entirely of carbon fibre – hull, foils, spars and fittings.

The Ten Rater class is managed by its own International Class Association, the ITCA. Please visit the class website at

Ten Rater Class documents (click to expand categories)

International One Metre Class

The International One Metre (IOM) is the most popular RC racing yacht in the world and is raced in over 30 countries.

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The class was created in 1988 by Jan Dejmo aided by Graham Bantock and the Technical Committee of the IMYRU (predecessor of IRSA).  It has continued to grow steadily since its creation.

Although carbon fibre is allowed in the construction of the fin and rudder, construction of the hull must be of either wood or glass fibre. Spars shall be of alloy or timber and the sails are to ‘One Design’ sizes. 

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The number of rigs is limited to three. This makes  the class very popular for amateur builders and many designers have plans for competitive boats. Builders who can supply kits for home completion or completed boats are plentiful.

The IOM class is managed by its own International Class Association, the IOMICA. Please visit the class website at 

IRSA Marblehead Class

The IRSA Marblehead (M) class is probably the most exciting to sail with its moderate size and light weight combined with high manoevrability and stability. Essentially a box rule with minimal constraints. A modern M will usually be made almost entirely of carbon fibre – hull, foils, spars and fittings. 

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The class was the first to adopt hi tech construction in the early 90s and  development since then has been limited. This permits almost all boats built since then to be compete well in modern fleets.

The class is quite often referred to as the “Formula One” of radio sailing.

The Marblehead class is managed by its own International Class Association, the IMCA. Please visit the class website at