Byron Software and Services

Sail Race Management : Cruiser Phrf and RYA PN correlation

Whilst boat handicapping is only a small part of [the 1990's release of ] our 'Sail Race Management' software, the topic is often the least understood and raises many emotive responses from competitors.

With limited race data available it is very difficult to differentiate between crew and boat performance. Statistically relevant data can be readily gathered for dinghies and 'one design' fleets, however, the range of cruiser types and configurations does create some difficulties. Setting a handicap for an unfamiliar/new boat type without an RYA PN, not using established marine ratio data, adjusting on subsequent races in the prescribed manner, can very easily produce anomalous values until sufficient time has elapsed to enable the RYA to gather and publish definitive data.

The objective is to use scientifically based mathematical relationships to economically allocate initial boat handicaps for clubs in an attempt to keep the peace and assure fair play. Handicap calculation routines [in 1998 ] are based on the Phrf regression formula and curve matching initially to RYA primary/secondary and recorded number cruiser values, that's PY, SY and RN. Calculations are offered free on completion of PN handicap data sheet.

The regression formula for predicting Phrf ratings from basic hull and rig specifications was developed by Terry "stats-man" Schell (and his university colleagues in the USA) from over 500 boats and their race results. The formula is in current use for 'base' calculations for several major Sailing Organisations in the USA. Thanks Terry for all your excellent work and allowing your research to be used here.

The following indicates the degree of correlation between RHN and established RYA PN handicaps across the normal range. Calculations are based [in 1998 ] on 'Displacement Sailing' which would account for certain discrepancies when a boat can exceed its Lwl speed.

[The 2004 update below replaces the table from the previous year(s) and shows the increasing confidence level with our program's results by including some vessels that can surf/plane/exceed their Lwl speed. The Knots column shows the conventional calculation for 'Cruising motor/sailing' and should not be confused with hull speeds derived from 'effective sailing length' nor 'rated length' nor any other dynamic speed value we calculate. We still decline to list/publish 'dinghy handicaps' while the RYA system continues to serve clubs well, but we do help clubs/associations privately with class rules, infringement calculations and initial/new dinghy handicap predictions ].

Please Note - Clubs may need to adjust a PN/RHN when allocating a club handicap to suit local conditions, of course reasons should be declared. RYA traditional abbreviations and variation allowances indicators are used, RHN includes the use of 'standard' spinnaker. Greater confidence is achieved in an RHN value when definitive rig data is available. [ Prior to 2007, the full Cruiser web lists indicated where rig data lacked confidence - all now resolved. ]

Updated: 07/2004

RYA PNClassKeelEngRHNuSA/DKnotsDispLwlBeamDraftSA I:J:K:P:E:
994Contessa 32 (py)fib299220.056.569500249.55.556237.212.67183510
1008Hunter F1 (tn)fob100828.266.03202720.247.814.73
24.127.3811.0227.310.99
943Hunter Impala (py)fob94423.986.44555423.089.175.584703510.4214.637.4211.52
1038Hunter Sonata (py)fob103822.316.17245821.28.54.5
23.781226.38.5
936J24 (py)bob93927.845.993100208.92437026.259.515.8339.75
1060Sadler 25 (py)fibf106321.135.87450019.178.754.67360319.916258.5
924Sigma 33 (py)fibf92421.866.87920026.2510.55.756003711.7516.74513
1207West Centaur (py)2kib3120514.096.18670021.38.43
32.3310.08734.7511.5
1014West GK 24 (py)fob101420.736.1718756.462.851.52318.552.593.99.453.05
1022West GK 24 (py)fibf102420.736.1718756.462.851.52318.552.593.99.453.05
 

Updated: 03/2007
The computer handicap calculation routine has been adjusted by 0.1% for 2007 as a result of a comparison exercise against all RYA Primary/Secondary and Recorded number boats (as there are only four 2007 PY boats, this category alone is not statistically relevant, so we needed the larger sample to provide better accuracy for the average sailor and boat), additional weighting was given to SY boats which statistically have better club handicap returns.

Updated: 03/2008
As a result of a comparison exercise against all RYA Primary/Secondary and Recorded number boats the computer handicap calculation routine has been adjusted again this year by 0.1% for 2008, plus some further differentiation for boats with other than the traditional fin keel.

Updated: 01/03/2010
Comparing data from Club, National and International Race events (including Echo/IRC data), has indicated that the computer handicap calculation function does not require any adjustment for 2010, hence the 2009 issued individual vessel ByPN calculations are still relevant. Further differentiation within non 'One Design' classes has been undertaken which has prompted the more detailed web calculation form to cover the 'less common' features that can have an impact on a vessels performance.

Updated: 28/03/2011
Comparing data from Club, National and International Race events (including Echo/IRC and VVF data) has prompted us to make some small changes to our software for 2011 handicaps, this has had the effect of improving handicaps for several 'smaller/lighter/less powerful' Classes, however, no adjustment has been necessary for other classes, hence the 2010 issued individual vessel ByPN calculations are still relevant. Of course, as our 'boat specification data' improves then some changes to the web listed upper quartile vessels will be evident.

Updated: 03/2012
Data comparison exercises have indicated that the computer handicap calculation function does not require any adjustment for 2012, however as our 'boat specification data' improves then some changes to the web listed upper quartile vessels will be evident.

Updated: 03/2013
Data comparison exercises have again indicated that the base computer handicap calculation function does not require any adjustment for 2013; some changes to the web listed upper quartile vessels will be evident as our 'boat specification data' continues to improve; the SA/D calculation now uses the vessel's 'on the water' displacement (with fuel/water/stores and crew included) so it's more realistic than just using the usual 'light boat' displacement.

Updated: 14/04/2014
Base computer handicap calculations remain the same, but as a result of research into hull/appendage coefficients some minor changes to the metacentric height calculation in both the Regression and VPP modules have been made, changes effect performance vessels most but differences are only a few percent; larger changes are the result of more powerful versions of a listed class being identified. A change to our 'web list' selection criteria has also been implemented to help viewing on mobile devices, entries are being restricted to the more popular handicap racing boat classes.

Updated: 04/2015
Base computer handicap calculations remain the same, but as a result of research into hull/appendage coefficients some minor changes have been made.

Updated: 04/2016
Base computer handicap calculations remain the same, but as a result of research into multiple appendage coefficients some additional categories have been found to be necessary.

Updated: 04/2017
Some changes to ByCN's as our 'boat specification data' continues to improve; Race Category listing now published and pages now include 'sponsors' content.

Updated: 04/2018
Additions and some changes to ByCN's as our 'boat specification data' continues to improve; revision control now on a per page/monthly basis rather than annually.


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