From the Technical Committee: CRF MkII Update
Classic yacht owners often ask, ‘Why do I have to revalidate our CRF MkII certificate every year?’
A: One reason is that since CRF relies entirely on owner declared data, it is important that they have the opportunity to review their declarations each year to be sure that they accurately reflect the way that they plan to race their boat in the upcoming season, and that those declarations include any changes, such as a new, bigger headsail added over the winter. Another reason is that since we routinely refine the factors and formulae underlying the CRF MkII ratings each year, ratings can change slightly from one season to the next, which makes it imperative that everyone be racing with a certificate issued under the latest version of the rule.
This of course begs the question, ‘Why is my CRF MkII rating different this year when I didn’t change anything?’
A: The factors and formulae are reviewed each year and refined as appropriate, based on an in depth analysis of the sailing conditions and race results experienced during previous seasons. The intent of any resulting refinements is always to provide more equitable racing via addressing any perceived rating biases due to specific yacht characteristics or combinations of characteristics, while avoiding the unintended consequence of disrupting the overall competitive balance across the fleet. Typically, any year-to-year refinements are quite small. For 2019, the rig factors for ‘split rigs’ (yawls, ketches, and schooners) were reduced, the keel factors for full keels were increased very slightly, the rig factors for wooden masts were reduced, and small adjustments were made to both the Draft and Length/Beam Ratio corrections. There are two more significant changes to CRF MkII for 2019, however:
First, a Stability Correction has been added that is based on currently declared data, that assesses the stability generated by both the hull and the crew, and that speeds up the ratings of yachts with high stability.
Second, modern yachts with broad, powerful afterbodies have been observed to have been rated too slow under previous various versions of CRF MkII. To address this bias, yachts designed after 1990 with unusually broad beam aft have an increment added to rated ‘L’ to address the higher effective sailing length of these more powerful stern shapes. In order to implement this refinement, yachts designed since January 1, 1990 only will be required to declare a ‘Bm10’, a new deck beam measurement at the aft end of the waterplane.
All this suggests a third question: ‘What additional information will I be required to declare in the 2019 CRF MkII application, and will that new data impact my rating?’
A: There will be three new data declarations required:
- Ballast weight; for 2019, this request is for data gathering purposes only, and its declared value does not affect 2019 ratings. It will likely be used to refine the 2019 Stability Correction for 2020.
- Standing rigging material; as with ballast weight, for 2019 this request is for data gathering purposes only, and its declared value does not affect 2019 ratings. I can be expected to have a small effect on some 2020 ratings.
- Bm10; a ‘deck beam at the aft end of the waterplane’ is required only for yachts with a design date of January 1, 1990 or later. It will ‘speed up’ the ratings of a handful of contemporary designs with unusually broad and powerful afterbodies.
The CYOA Technical Committee is always happy to discuss any technical questions you have, and the CRF site offers an opportunity for rating inquiries.
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