CRF (Classic Rating Formula) was developed as a measurement system for rating yachts of varying types and sizes with traditional, full-keeled designs. Generally based on the old Off Soundings Rule, it was first used for the Opera House Cup and then later for all classic events in New England.
Over the years, as the classic yachting community has grown, adjustments to CRF have been made to accommodate different boats. In 2016, the Classic Yacht Owners Association (CYOA) formed a technical committee to review CRF versus other rating alternatives including PHRF, Europe’s CIM, and an ORC VPP-based system. The group quickly recognized that current CRF ratings provide a reasonable reflection of the real world performance potential of some yachts within classes of similar sizes and types. However, the Committee also recognized that there are notable exceptions, and as a means of addressing these shortcomings, the Committee developed a comprehensive reformulation of CRF that has been dubbed ‘CRF MkII’. The formulae underlying the MkII proposal are based on the CRF 2016 data requirements.
A CRF MkII rating continues to be based on owner-supplied measurement inputs and is not impacted by past or subjective performance criteria. A CRF MkII rating is expressed on the certificate both in decimal feet and in seconds per mile. With the development of CRF MkII, and with continual review by the Technical Committee, we expect CRF MkII ratings will be as accurate, objective and transparent as possible.
CYOA 2018-2019 Technical Committee
- Simon Davidson, Chair
- Adam Langerman
- Joe Loughborough
- Brad Read
- Bob Stephens
- Greg Stewart
- Jim Taylor
- Susan Wayne
- Steve White
About the CRF MKII FORMULAE
CRF MkII Background, Formulae, and Factors
The primary goals for CRF MkII are better handicapping, continuity with previous versions of CRF, and transparency. The expectation is that CRF MkII ratings will better reflect real world performance potential via the following improvements over earlier versions of CRF:
- Assessing effective sailing length at its full linear value rather than at its square root, resulting in ratings that are similar to LWL, and thus better suited to the Herreshoff TA tables typically used in scoring Classic races.
- Assessing effective sailing length by weighting LWL more heavily than LOA, since length at deck level is seldom immersed or fully effective in generating sailing length.
- Assessing the primary performance parameters draft (including ‘board down’ draft for centerboarders) and displacement directly in its new formulae, rather than by applying ‘Adjustments to Base Rating’ (ABR’s) and/or ‘Cruising Adjustments’.
- Retaining a length/beam term in calculating rating, but basing it on a smooth curve and an assumed ‘base length/beam ratio’ that varies with length, rather than on a step function.
- Assessing genoa overlap in calculating ‘with spinnaker’ ratings.
CRF MkII is careful to maintain continuity with CRF’s previous versions in several ways, as it is fully recognized that without the decades of hard work by Chris Wick and others in the development and administration of CRF, there would be no Classic racing as we enjoy it today. This continuity is maintained first by the fact that both versions share ‘development DNA” with the Cruising Club of America (CCA) rating rule. In original CRF the CCA connection is quite direct, and in MkII it is maintained through the CCA rule’s contributions to the IOR rule, on which CRF MkII is loosely based. Continuity is further maintained by the fact that CRF MkII requires only the following data input declarations beyond those that have been required in earlier versions of CRF.
- Centerboard extension beyond fixed keel draft. (CRF’16 does not account for ‘board down’ draft)
- Distance from the mast to the tack point of an asymmetrical spinnaker, if one is carried while racing
- A ‘closest match to sample sketches’ declaration for a range of keel and rudder configurations.
- A ‘square head’ mainsail type declaration (only allowed on Spirit of Tradition yachts)
- An off center exposed propeller option
- A ‘trim tab’ (adjustable flap on a keel trailing edge) option
CRF MkII intends to make its development and administration as transparent as possible. This will be done most simply by avoiding the application of undocumented ABR’s and Cruiser Adjustments to MkII ratings, and more fundamentally by calculating ratings via published formulae and factors, (see below) rather than via an unpublished ‘black box’. For those without the time or inclination to wade through the formulae shown, a short text summery of how they are constructed follows:
- A ‘base rating’ is calculated first. Its most important initial term carries the performance contributors length ‘L’ and the square root of rated sail area ‘S’ in the numerator, and the performance limiter displacement ‘DSPS’ in the denominator, much as in Nathaniel Herreshoff’s Universal Rule and later in IOR. This first term is then adjusted by a Draft Correction ‘DC’ and a Length/Beam Correction ‘LBRC’.
- The final CRF MkII rating is calculated by applying Propeller, Displacement/Length, Sail Area/Displacement, Keel, Spar, and Moveable Appendage factors to the base rating. MkII retains the general approach of the earlier version of CRF in the Rig and Propeller Factors, but the other factors are new in CRF MkII.L
Frequently Asked Questions
A. For most yachts, the data declarations for 2019 will be the same as those required in 2017 and 2018, and that data will auto-load for your 2019 application. For catboats and some additional inputs will be required.
A. Although the application is processed automatically for a rating, to ensure accuracy each certificate will be manually reviewed before it is issued. Plan on at least 5-7 business days, and if applying during July and August, it may take longer due to a larger number of certificates being issued.
A. Once processed,
A. No. A boat will be allowed one configuration change only during any one season. A new CRF MkII certificate reflecting that one change must be issued at least 10 days before the next race in which the boat competes, and the boat may not revert back to her original configuration later in the same season. (This ‘one change’ limitation does not preclude correcting errors or making minor updates to declarations, which may be accepted and a new certificate issued, at the discretion of CRF administration).
Q. I’ve made a mistake on measurements on my application, and my certificate has been issued. What do I do?
A. File an inquiry and see our process here. Your request will be reviewed by CRF handicappers, and if there is an error, they will notify you, make the change in the data, and reissue your rating with the corrected measurements.
A. First, while it is possible that an input error has been made, be aware that for 2019, ratings for all yachts will be different than both their previous CRF rating and in many instances from their 2017 and 2018 CRF MkII rating. In some instances relative to past comparable yachts, ratings may vary a great deal. Additional variables have been used in calculating the CRF MkII, plus all subjective measurements have been eliminated so ratings may not be comparable to past years. As for differences from the 2018 CRF MkII rating, the 2019 formulae have been adjusted to correct for observed biases in the 2018 formula. Specifically, a more powerful Length/Beam Correction together with some minor adjustments to the Disp/Length and Sa/Disp factors, along with underbody and mast material have been made. There is also a reduction in the rating ‘charge’ for
Of course, it is also possible that an error in data input has been made. If you feel that this is the case, file an inquiry CRF handicappers will review if there is an error. If so they will notify you, correct the rating, and reissue you a new certificate.
Q. I believe the rating on a competitor’s yacht is wrong. How can I confirm if the rating is accurate?
A. For 2019, ratings for all yachts will be different than the previous CRF rating, and in some instances relative to past comparable yachts, ratings may vary a great deal. Additional variables have been used in calculating the CRF MkII, plus all subjective measurements have been eliminated so ratings may not be comparable to past years. It is also possible that an error in data input has been made. File an inquiry CRF handicappers will review, and if there is an error, they will notify the yacht owner of the error and any resulting change in rating. If the measurement in question needs verification from an independent outside source, a measurer will be hired at the expense of the appealing party.
A. Certificates of all currently registered classic yachts may be viewed by going to the CERTIFICATES CRF Database.
A. The fee for a rating certificate is $50, and you must renew your certificate every year so that your rating reflects any changes to the formulae.
Q. My 2019 rating is different from my 2018 rating, and my measurements are the same. Why? What caused the change?
A. The 2019 formula has been modified to reflect biases that were identified by an objective, in-depth analysis of 2017 and 2018 race results. Specifically, yachts with a relatively narrow beam and heavy displacement (e.g. Universal and International rule racers) were observed to be advantaged, while yachts with an unusually deep draft, via either a fixed keel or centerboard, were observed to be disadvantaged. The 2019 CRF MkII ratings for nearly all yachts will change relative to their 2018 ratings, but most only slightly. Those that see a significant change will find that other yachts of the same type will have changed by a similar amount, so the competitive balance within groups should be maintained.
A. Ratings need to be renewed annually as the formula is continuously being tweaked based on new race data.
Hull and Underbody Questions (5)
Q. The only information that I have on displacement for my yacht comes from original design specification. How can I update that to a current ‘as raced’ weight?
A. Designers and builders typically provide displacement data referenced to the ‘design waterline’ that most often resembles a ‘light ship’ condition, with empty tanks and minimal food and gear. The weight added in equipping and provisioning for coastal cruising can increase that displacement by 10%. The boat hauling equipment in some yards can provide a boat weight, but these weights are typically not especially accurate, and should be used as a rough reality check only.
Q. I have determined that the displacement of my yacht is heavier than that shown in the designer/builder specifications. How does this affect the other CHR MkII data declarations that I need to make?
A. If you are declaring a displacement that is heavier than the designer/builder specification, it follows that your declaration for the LWL that corresponds to that heavier displacement should be longer, and that your declaration for Draft should be deeper, than the designer/builder specified values. One way to quantify the differences in LWL and Draft (DM) would be to estimate the sinkage resulting from the difference between the designer/builder spec and the declared displacement (DSPS). The ‘Pounds per Inch Immersion’ (sink) for most boats can be approximated by: Lbs/in Immer = 1.1*LWL^2. It follows that actual sinkage (in inches) = delta DSPS/Lbs per In Immer. This estimated sinkage would equal to the amount added to the designer/builder specified Draft (DM) in inches , and for most boats multiplying this sinkage by 6 approximates the amount added to the designer/builder specified LWL, also in inches.
Q. The ‘Underbody Type’ declaration is new with CRF MkII. Why has this been added to the rating application?
A. Stability and wetted area are critically important performance parameters, but it is not reasonable or practical to ask owners to declare appropriate values for them. The 6 underbody types displayed on the CRF rating application work as surrogates for stability (via related keel volume, VCB and VCG), and for wetted area more directly. In addition, the various underbody type options help account for the advantages of a high aspect ratio fin with separated spade rudder over a lower aspect ratio configurations, including a full keel with an attached rudder.
Q. I have a yacht with a centerboard, and none of the keel profile sketches displayed in the rating application show a centerboard. What keel type should I declare?
A. Check the box corresponding to the underbody profile that most closely resembles the fixed portion of your keel. CRF MkII accounts for the effect of the centerboard via the declared value for ‘Draft Centerboard Down’.
Q. I am unsure of whether the underbody of my yacht should be declared as a ‘Type 3’ (fin keel with a separated spade rudder) or ‘Type 4’ (fin keel with a skeg rudder). Please elaborate.
A. The critical detail that would imply a ‘Type 3’ underbody would be the fact that the rudder is a
Rig and Sail Questions (8)
Q. Can you clarify the difference between the declared heights of jib headed and gaff headed mainsails?
A. The height of a jib headed mainsail is declared as ‘P’, which is essentially the luff length of the sail. The height of a gaff headed mainsail is declared as ‘PG’, which is the height from the mainsail tack to either the peak halyard block, or to head of a topsail (if carried), whichever is higher.
Q. Some previously ‘square head’ mainsails in the Spirit of Tradition (SOT) class were converted to gaff headed sails and were rated as such in 2016. How will such conversions be dealt with under CRF MkII?
A. Under CRF MkII, gaff headed mainsails in the SOT class will be rated as ‘square headed’. Exceptions to this approach are possible in cases where the sail configuration is very intentionally designed to have an entirely traditional appearance, with the gaff length on the order of 2/3 that of the boom length. However, any such exceptions shall only be made after special consideration by, and at the discretion of, the rating authority.
A. A spinnaker is any sail set forward of the foremost mast whose width, measured between the midpoints of its luff and leech, is equal to or greater than 75% of its foot length. (See RRS 50.4)
Q. In light air, I plan to fly a headsail whose mid girth is less than 75% of its foot length, but it is too big to fit inside the nominal foretriangle. What should my declarations be for foretriangle height (IG), foretriangle base (J), and longest perpendicular, LP?
A. This sail is by definition a headsail and not a spinnaker (See RRS 50.4), and CRF MkII will rate it as a headsail. For such a sail, ‘IG’ would be declared as the vertical distance from the sheerline to the top of the sheave supporting its halyard, and not to the upper end of the nominal foretriangle headstay. Similarly, for such a sail, ‘J’ would be declared as the horizontal distance from the forward face of the mast to the attachment point for its tack on the deck or bowsprit, and not to the nominal forestay headstay tang at the deck. And finally, the LP of this sail would be the distance from its clew to its luff, measured perpendicular to the luff, and not the LP of a smaller sail set in the nominal foretriangle. Note that CRF MkII will rate the speed potential of the boat with this sail in its best condition, and that the rating with such a sail will be ‘faster’ than it would be with a smaller headsail set in the nominal foretriangle, even when only that smaller sail is flown. Note further that some race organizers will require that such a headsail must have its luff attached to a stay, and that it cannot be set free flying.
Q. The declaration for the tack point of an asymmetrical spinnaker (TPS) is new. Can you explain its definition and use?
A. ‘TPS’ is the distance from the forward face of the mast to the attachment point for an a-sail tack to the deck, to an anchor roller, to a bowsprit, or to a similar fixture. If an a-sail is tacked to the stem near the headstay tang, ‘TPS’ is nearly equal to ‘J’, the length of the foretriangle base. If an a-sail is tacked further forward to the end of an overhanging stem or to a bowsprit, ‘TPS’ will be significantly larger than ‘J’, the rated area of that a-sail will be bigger, and the rating will be faster. Under CRF MkII the change in rating for increasing ‘TPS’ is generally in line with that of other handicapping systems.
A. Any pole used in trimming a spinnaker is a spinnaker pole, and it is rated as such with its overall length declared as ‘SPL’. A whisker pole is a pole used to wing out headsails only, and its length is limited to not more than 1.1*’J’. A spinnaker pole with a declared length not longer than 1.1*’J’ can be used as a whisker pole to trim headsails. A boat can use a spinnaker pole with either symmetrical or asymmetrical spinnakers, but if a spinnaker pole is declared, the boat will be rated for an s-sail spinnaker area, whether or not she actually carries any s-sails.
A. Yes, as long as you declare a spinnaker pole length ‘SPL’. If you declare both a pole length ‘SPL’ and a spinnaker tack point ‘TPS’, CRF MkII will calculate a spinnaker area for both an s-sail via SPL, and an a-sail via TPS, and it will calculate rating on whichever area is larger.
A. Yes, as long as you declare a spinnaker pole length ‘SPL’. Note that a whisker pole can only be used to wing out a headsail, and not to trim a spinnaker. Also, be aware that if you do declare an ‘SPL’, your calculated spinnaker area will be larger, and your rating will be