A Proposed National Keelboat Rating System
General overview: This is a measurement-based system with the basic hull and sail specifications being obtained from formal measurement systems such as IRC, IMS, ORC International, Naval architect design specifications, sailmakers, and, finally, sales brochures.
Basic hull performance rating:
All data extracted from the above is summarised, reviewed, corrected for any apparent errors and entered into the system.
The system/formula takes the above measures and calculates the upwind and downwind immersed waterline length’s, and applies a derivative of the SA/D (sail area / displacement ratio) to extract a deemed upwind and downwind speed relationship across the full range of yachts. The “scratch” yacht is the Lavranos-designed L-34 at 1.015 deemed rating.