Handicap (PN)





 4.74m (15ft 7in)

     crew > 78kg 


 Beam no wings

 1.75m (5ft 9in)

     helm+crew < 135kg


 Beam with wings

 2m (6ft 7in)


 choose for the event


 14.3m2 (154 sq ft)



 18.8m2 (202 sq ft)



The ISO is a former International Sailing Federation (ISAF) class of two-person sailing dinghy with a single trapeze and an asymmetric spinnaker. The ISO was designed in 1993 by Ian Howlett and John Caig and manufactured by Reg White Limited of Brightlingsea as part of the "White Formula" range of boats originally marketed by Topper International Ltd and since 2013 by Vantage Sailing Ltd. The boat has a fully battened mainsail, jib and an asymmetric spinnaker.

The name ISO reflects a feature of the design that allows different sized crews to compete on an equal basis. This is achieved by a crew weight equalisation system consisting of removable wings. The wings may not be used if the trapezing crew weighs more than 78kg (to equalise righting moment) and must be used if the combined helm and crew weight is less than 135kg (to equalise weight in the boat). If neither of these mandatory rules apply the crew may choose whether or not to use wings but may not change this decision during a race series.

Around 700 boats were built with sail numbers starting at 501. The ISO is designed to be a relatively easy boat to sail for its performance level. It belongs to the racing skiff category. In the UK the ISO Class Association is affiliated to the Royal Yachting Association (RYA).