Saturday, 6 August 2011

Target Times at the WPIR

28182 The Sailing Instructions at most events give a specific (approximate) time the races should last. Those are called: “Target Times” For some classes it is longer than for others, but in all cases it is the job of the RO on the course to set his/her marks so, that this time is accurate. There are unforeseen circumstance but with a constant wind speed and knowing the class these Target Times can be calculated.

Some time ago I was given the spreadsheets that do just that, for the Olympic Classes. They were made by David Cambell James. This is what he says on the first tab:

“ These charts have been developed to assist Race Officers in setting courses of the correct length to achieve target times as accurately as possible, they are only a guide and do not take account of tide or difficult sea conditions. It is assumed that the standard Olympic courses are used and set up using the “reference point” system with the reach leg at two thirds of the windward leg length and the final reach of 0.15 nm.

These charts will be particularly helpful to Race Officers who are unused to running races for a particular class as can happen when medal races are required. Race Officers experienced in a particular class may find the charts of less help.

The newest chart is the one for Women’s Match Racing which is difficult as target times and leg lengths are short and speeds can be inconsistent. We will continue to work on this chart.

The difficulties of producing these charts is increased for classes such as RS:X and 49ers where the hull moves into more of a planing mode between 8 and 10 knots with the corresponding increase in speed.

Included in the pack are two data collection sheets which can be used to check or adjust speeds included in the charts. By going to the overall speeds page any amendment of speed, measured in minutes per mile, will automatically update the relevant speed chart. If you have good speed data on a particular chart please let me know so that we can update the master sheets.   
I would like to thank Peter Baldwin for his help in collecting data and producing the charts.  Please contact me if you have queries, comments or any update information.   
David Campbell James “

The file: Target Times for Olympic Classes version 3 dated April 2011.xls

You can download this file and us it for you own races. It might need some adjustment for your particular courses and classes, but even for those who do not run Olympic Classes it should be a tool that can be used. You will need to start gathering data on your specifics, but with that you can fiddle with the numbers.

TTime Finn Trap

Ooh, don’t forget to give David your assessment or pointers to improve. His mail address is on the first tab as well.

I’m catching the 08:30 bus to the venue.



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