Portsmouth Yardstick

UTLSC PNs 2021

UTLSC PNs are based on the RYA National PNs for each class – see below for how they are used.

As a result of the Coronavirus pandemic in 2020 the RYA has decided to freeze the 2020 numbers. Therefore there is no change to the PY list for 2021.

National PNs were not provided for classes marked with *s. The RYA have provided us with Trend data PNs for these classes in March 2020.

If a PN has been taken from a class website there is a link to the relevant page from the class name

ClassUTLSC 2021 PNNational 2020 PNSuggested PNConfidence LimitUTLSC 2020 PNIncrease
from 2019
Cherub (Veteran)114011400
Hartley 12.2*1188118811880
Laser 4.71188120811650.461190-2
Laser Radial1113114711040.81115-2
RS 2001047104610630.0510470
RS Aero 5113611361157011360
RS Aero 7106510651104010650
RS Aero 9101410141053010140
Streaker Wave*121711901227012170



Portsmouth Yardstick

Some classes are faster than others. E.g. A Laser is faster than a Topper.
To enable boats from different classes to compete against each other in the same race classes are given a Portsmouth Yardstick Number (PN).
These PNs are used to calculate a corrected time from the elapsed time. The person with the lowest corrected time is the winner and so on.

Corrected Time = Elapsed Time * 1000/ PN for that class


How are UTLSC PNs set?

For several years the RYA has been providing National PNs for many classes based on data from many sailing clubs.

UTLSC has been uploading results to the RYA since 2013. The RYA provides an analysis tool that gives a Suggested PN for each class based on UTLSC  data alone. At the same time the RYA recognises that if there is insufficient data provided the Suggested PN is not statistically sound, so they also provide a Confidence Limit for each class based on the volume and stability of the data.

2015 -2018

From 2015, at the recommendation of the RYA, UTLSC decided to use the Suggested PNs and Confidence Limits to calculate the UTLSC PNs for the following year.  For 2015 – 2018 the UTLSC PN moved from last year’s UTLSC PN towards the Suggested PN according to the Confidence Limit.
However if the Confidence Limit is 0 the National PN was used.

2019 onwards

There was concern that we are not making best use of the data collected nationally. So from 2019 the UTLSC PNs are calculated by by moving from the National PNs towards the Suggested PN according to the Confidence Limit.

UTLSC PN = National PN + ((Suggested PN – National PN) * Confidence Limit)

E.g. For the LASER

     National PN:         1099
     Suggested PN:      1070
    Confidence Limit:   77%

    UTLSC PN:   1077 = 1099 + ((1070-1099)*77%)