ANALYSIS OF YACHT PERFORMANCE UNDER THE IOR RULE: THE RELATIONSHIP BETWEEN GEOMETRY AND SPEED POTENTIAL

摘要

The International Offshore rule (IOR) provided a handicapping system for racing yacht between 1972 and 1994. Duringthis period great advances in both the materials used in construction and designs specifically to the rule, were made. Thepopular press discussed, at great length, how loopholes in the rules were exploited to gain a favourable rating. This led tothe perception that the exploitation of geometric measurements was leading to boats with poor performance characteristics.This paper aims to address this, firstly through an analysis of the geometric parameters and their evolution through theearly part of the IOR era. The paper concludes by undertaking a velocity prediction analysis of a series of boats, atechnique that was in its infancy at the time these yachts were designed. The analyses show that the geometric parametersdid evolve with time, but not necessarily in line with the understanding behind good performance. Penalties in the ruledictated the direction of design. However, the performance analysis did show that judging yachts based on ratedcharacteristics could lead to misinterpretation, but in general, the performance data aligned reasonably well with assumedperformance in specific sailing conditions. The velocity prediction analysis also concluded that the performance of yachtsbetween 1972 and 1981 did increase regardless of the geometric form being dictated by the rules.