the ior rule encouraged wide short boats with limited stability. a narrow waterline and large beam on deck, combined with a high centre of gravity, meant that crew weight provided a significant proportion of stability at small heel angles, and boats had a relatively low angle of vanishing stability. this developed into the situation about 1977 when the boats winning in most smaller ior categories (up to the half tonners - about 10m loa) had all internal ballast, often with an unballasted daggerboard. the managers of the rule realised that this was not a suitable direction for seaworthy yachts, and heavily penalised boats with lifting keels, but not before the 1979 fastnet race ended in disaster. writes john rousmaniere: