CLUB PY

ASC CLUB PORTSMOUTH YARDSTICK RATINGS EXPLAINED

Aylesbury Sailing Club operates a Portsmouth Yardstick (PY) rating system to encourage fair and competitive racing between boats of different types. 

What is the Portsmouth Yardstick?

The Portsmouth Yardstick System aims to handicap boats based on their relative performance to the other boats they race. Handicaps are allocated and administered by clubs and are influenced by local factors such as boat type, wind trends and water type. For more information see here.

Every type of boat is allocated a 3 or 4 digit PY.  The slower the boat design, the higher the PY number.  At the end of a race between different kinds of boat, each boat’s finishing time in seconds is divided by the PY for that boat and then multiplied by 1000, to give a “corrected” time which is used to rank the finishing order of the boats.  This means that a relatively slow boat like a Mirror or RS Quba may finish ‘on the water’ some minutes behind a faster boat like a Laser, but may end up beating the faster boat on corrected time once the PY adjustment has been applied.  In other words, two helms of equal skill sailing different boats may finish far apart on the water but ought to be placed quite close to each other on corrected time.

How is it calculated?

The PY is calculated by the RYA’s calculator which relies on results from races being uploaded to its website (pyonline.org.uk) and statistically analysed by the RYA’s algorithm to work out the average performance of different boats when sailed against each other.  The RYA publishes the national PY tables in the spring of each year.  Those national PY tables are based on the average of thousands of individual race results from boats which have been sailed in many different places: from tidal racing on the sea, to rivers, and even to tiny ponds such as Weston Turville Reservoir.

Although the RYA full PY tables are fair when applied to national open series of races which are held over the course of the season in many different locations, they do not necessarily promote fair or competitive racing between club boats which always sail on the same piece of water with its own particular peculiarities.

The RYA therefore encourages clubs to adapt the PY applied to their own particular club racing.  The pyonline.org.uk calculator allows clubs to do this by performing the PY analysis to the results of the boats sailing at a particular club, thereby generating a club specific PY.

What are the criteria for a race to be included in the overall PY calculations?

A race must fulfil the following criteria:

• Needs to have more than 3 finishers
• Must have more than one Class
• Must not less than 20 minutes

Who is included in the PY Calculations?

Only top 66% of finishers are used to calculate the average corrected time.

Only those that finish within 105% of the average corrected time of top 66% of finishers are counted.

How is the PY for club races selected?

ASC is a small club with relatively few boats racing on any given day.  The Solo class is by far the largest fleet and dominates the results.  Most classes of boat are represented by only a small number of boats in each race.  This means that the set of results used for the club PY calculations of most classes of boat is small.  The statistical accuracy of the PY calculations for all classes other than Solos is, currently, of limited reliability. 

Accordingly, club races will for the time being continue to have results calculated using the general RYA national PY tables.  In order to build up  larger data set of results for a more reliable local club PY to be calculated for all classes some race series will have a set of ‘shadow’ results published alongside the ‘official’ results.  The shadow results will be based on adjusted PYs based on those indicated for the club by the PYOnline calculator.  Over time these shadow results will permit a reliable club PY to emerge which can be applied to all racing. You can see these shadow or trial results on the results page where they can be compared to the ‘official’ results.

Club PYs will require regular review because the average performance of different types of boat in a small club is disproportionately affected by changes to the relative skill levels of the sailors in each fleet than is the case across the national RYA averages where there are far more sailors providing a more accurate average.

The Sailing Committee will therefore regularly apply their judgment to the RYA’s statistical analysis of our racing results, and the actual results produced by the local club PY, in order to set PY numbers for each boat which appear to be fair and competitive.  As the season progresses the Committee will review the results and adjust the PY for each class may be necessary to ensure competitive and fair racing.

A full summary of the PY applied to the common classes of boat sailed at ASC is available HERE and a copy is posted on the clubhouse noticeboard.

Please speak to the Sailing Secretary if you have any questions.