boats had a short competitive life for two reasons: the overall increase in performance of newer boats due to better design and construction, and also the effect of changes in the handicapping rules. the first was catered for by an "age allowance", which reduced the handicap of boats as they got older. the second was catered for to some extent by grandfather clauses in the ior rules, but this did not cater for designer's ability to design to the rule increasing with every year. this, plus the annual rule changes, gave boats a competitive life of no more than 2 or 3 years at the top level.