predicted as the best sail upwind. The ITC will continue to develop the aerodynamic force model to deal with the effects of rigging enve- lope, sheeting base and use of outriggers on headsail performance. The rules about the use of whisker poles to leeward seem to be honoured more in the breach than the observance. A whisker pole to leeward must be attached to the clew of the jib and the mast. You cannot rig a spar to leeward as a sheet deflector. Scoring is the ‘holy grail’ (or ‘bête noire’) of ORC handicapping. To get the fairest result when handicapping boats based on their Polar Curves the scorer needs to know what the wind speed and direction were, and the course layout. Absent this information and the scorer falls back on the All Purpose Handicap (APH), derived from an average of the polar table wind speeds and points of sail. For any race scored using a constructed course and observed or implied wind the APH is always going to be in error. This adds a random element where some boats benefit and others lose out if the APH is used.
In the UK this seems a part of the rough and tumble of racing: every dog can have his day, or not. In the USA there is a growing acknowledgement that if you use a single number there are some perfectly well-bred dogs that never get their day, so they have a myriad ratings on their certificates based on a diverse range of course model options. Regardless of approach, ORC sailors want to see scoring based on the polar curves and course conditions. In 2022 there was a submission from the USA that proposed using the course geometry and forecast wind to predict an optimum route for each boat around the course. The predicted elapsed time (PET) could then be used to create a table of time allowances to be applied to the actual elapsed time. Retrospectively scoring races from 2023 shows that the PET is almost always closer to the elapsed time than the APH-x-course length, which suggests that scoring on this basis would be more equitable and the scratch sheet would be available before the race.
The practical problems are legion but ORC has moved on to produce a scoring system that combines the ORC polar table with the Predict Wind forecast and routeing engine. Also on the menu is a somewhat contentious submission to
remove the RORC’s ‘SSS’ from the Offshore Special Regulations (OSR). First some background: after the 1979 Fastnet my colleagues and I at the Wolfson Unit used tests in breaking waves to understand the mechanisms of sailing yacht capsize. This work was supported by the RORC. The fundamental of robust resistance to capsize is the yacht’s righting moment curve, and particularly the Angle of Vanishing Stability (AVS). All other design features are second order. While these experiments were being done and the new regulations devised the RORC devised a ‘Stability Screening’ formula, SSS, as part of their Channel Handicap rating rule. This uses the boat’s dimensions as input, and these SSS limits were added to the OSR. Eventually, the regulatory authorities digested the data. First out of the blocks was the UK Maritime and Coastguard Agency. Their rules for commercial sailing yachts under 24m simply set out safe zones on a plot of Required AVS against LOA, shorter boats need higher AVS, and AVS can be lowered if you sail in sheltered waters. Eventually ISO standards were also produced.
The STIX formulation is more complex, not better than MCA, just harder to understand. The ORC handicap certificate has always needed a righting moment for the yacht, and it displays a ‘Stability Index’ that can be used.
There it is – all the regulations for every vessel from a J/24 to
the QE2 rely on knowing the righting moment curve. This can only be calculated if you know the yacht’s vertical centre of gravity posi- tion. The ORC’s analysis of the 2023 Fastnet fleet showed that the SSS screening would have passed many yachts that failed the AVS- based methods. This is not an acceptable situation. Now ORC wants to help fix the situation. SSS was born from good intentions, but now it is an accident waiting to happen. The ORC handicapping process derives the vertical centre of gravity of every boat. We have a huge database of hull shapes and VCG data that contains many of the classes that enter RORC races. Of course, defining the righting arm curve for any boat takes time and therefore money, but in many cases the costs will be hundreds, not thousands of pounds. It’s time to do the right thing, we owe it to the owners, their crews and their parents. Andy Claughton, ITC Chair
SEAHORSE 35
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