CYOA Technical Committee makes changes to CRF for 2025

IYRS Classic Yacht Regatta © Stephen R Cloutier

At the end of each Classic season, the CYOA Technical Committee does an in-depth review of the year's racing, with a primary focus on how accurately CRF ratings reflected real world performance over the full range of boat sizes and types and in a variety of conditions.

Unfortunately, for the second year in a row the weather gods failed to provide much wind for much of the season, so the amount of good data on which to base this analysis was limited. A quite different measure of success might be that the number of certificates issued in 2024 increased by almost 8% from 2023 and was the third highest in the 'CRF MkII' era. Even more encouraging is the fact that the number of discrete boats entering an event was almost the same as the number of certificates issued. All of this suggests that owners felt that their CRF 2024 rating reflected reality well enough to give them a fair chance on the race course. At the same time, despite all these positive developments, the cold hard facts are that accurately rating boats as diverse as those in the CYOA fleet is a tall order, so even if CRF 2024 did well, there is always room for improvement. Toward that end, the Technical Committee does plan on some changes to CRF 2024 that they hope will provide even better racing under CRF 2025.

In recent years it has been observed that boats in the Classic division have had a hard time competing in fleet scoring against their close cousins racing in Vintage.

The reasons for this have been puzzling, however, as these two Divisions generally share quite similar characteristics; their overall hull proportions are similar, they both have full keels with attached rudders, and they share similar performance parameters. There was not much data from the 2024 racing that was useful in resolving this dilemma, but a close look at the characteristics of about 50 boats that have both CRF 2024 and VPP-based certificates did prove to be very helpful in this regard. While the ratings calculated by CRF based on owner declared data are generally quite similar to those generated by VPP's based on full measurement, it did appear that the CRF ratings for Classic Division boats were often less advantageous as compared to their VPP ratings. This observation led to the identification of the following three characteristics that are typically different for boats in the Classic division relative to those in Vintage, and to a fresh look at the performance and rating implications for each:

• Spinnaker configuration: Many Classics race with symmetric spinnakers tacked to a conventional pole, while Vintage boats are more likely set up for asymmetrical chutes tacked on the centerline. A review of the CRF calculations for the rated area of both chute types revealed that CRF has been slightly overweighting the effective area of S-sails, and significantly underweighting that of A-sails. Revised code that is part of CRF 2025 will better reflect the relative drive forces of the two types. In so doing, it will slow up the ratings of boats flying just S-sails by about 1 sec/mi, while speeding up the ratings of those flying just A-sails by around 2 sec/mi.

• Spar Materials: Most Classics were built with aluminum masts, while most Vintage spars are wood. In the 'CRF MkII' era ratings have reflected a difference in performance potential from different mast materials, but they likely have not fully accounted for the fact that early aluminum masts for Classics are typically heavy, large diameter tubes supported by single spreaders. Acknowledging that the weight and implied performance advantages of this generation of aluminum masts over their wooden counterparts are modest, the Spar Material Factor for aluminum will be reduced in CRF 2025. This will slow the ratings of boats with aluminum spars by about 2 sec/mi.

• Propeller Installations: The propellers of boats in the Classic Division are typically housed in an aperture between the keel and the rudder, while most Vintage boats are configured with an exposed shaft and strut that are installed off center, so that the hull surface is uninterrupted as the keel blends into the rudder. A prop 'hidden' in an aperture does not have much drag in and of itself, but the blunt, thick perimeter of such an aperture leaves a big turbulent wake behind it that represents a lot of drag and that reduces the efficiency of the rudder. For CRF 2025, the Propeller Factors have been adjusted to better reflect the differences in drag between various 'in aperture' and other prop installations. The rating of a Classic with a typical 'in aperture' prop will be slowed up relative to that of a Vintage boat with an exposed, off-center installation by between 4 and 6 sec/mi.

Beyond the changes summarized above, there are two additional refinements built into CRF 2025. The first of these deals with the use of mizzen staysails, that to date has been 'free' in terms of CRF rating. This was a conscious choice made during the development of 'CRF MkII' to ignore these sails in the interest of simplicity, but the result has been that boats flying them have been given an unrated advantage off the wind. In 2025, the on-line procedure for applying for or renewing a CRF certificate will include a yes/no question as to whether or not a yawl or ketch wishes to have the option of flying a staysail from her mizzen mast. if a yacht's answer is 'yes', her downwind sail area will be increased by an amount based on the area of her 'fore and aft' mizzen in CRF 2025, and 'with mizzen staysail' ratings will get sped up by about 3 sec/mi for most yawls, and by a bit more for ketches.

A second minor change for CRF 2025 will affect just a handful of boats in the SoT and Contemporary divisions. Recognizing the advantages that the broad, powerful sterns of some modern hulls provide in terms of stability and added sailing length, starting in 2019 CRF required boats that were designed after 1990 to declare a value for 'Bm10', the deck beam at the aft end of the waterline. If a yacht's declared Bm10 value is greater than 75% of her maximum beam, an increment has been added to her effective sailing length that increases exponentially as Bm10 approaches BMax. The effect on rating has been significant for a few boats in the SoT and Contemporary Divisions, and this will be reduced in 2025. The CRF 2025 ratings for a few Contemporary boats (eg Jax and Outlier) will be slowed down by about 2 sec/mi, but the change will be over 7 sec/mi for some boats that are more dramatically broad aft such as Hopgrasser and Arcadia.

The Technical Committee is confident that the net effect of these changes for CRF 2025 will provide fun competition across the CYOA fleet that will be even closer than it has been in the past, and we hope that we all will see more wind on the races course!

Want to learn more about these changes? Join us for a Live Zoom Chat on February 20th at 6:30pm.