At Dahlgren Yacht Club, we have weeknight PHRF racing and have been using the standard Appendix A, PHRF Time-On-Time scoring for the Spinnaker and Non-Spinnaker fleets. We also wanted to be able to combine the fleet results into an Overall fleet as well. To try to better level the field, we give the Non-Spinnakers a handicap that is 110% of their base PHRF rounded up to the next multiple of 3 seconds. In addition, we encourage different courses for each fleet to try to result in similar wind conditions and elapsed times. The course distances could be different and are not necessarily a multiple number of laps of a single course.
Up until this Spring, we used a custom excel based scoring system, that artificially created an Overall Fleet result by combining the individual results of each competitor in each fleet by computing the achieved Seconds Per Mile for that night. It was not obvious on how to set this up in Sailwave, but Jon Eskdale recommended an approach that appears to do this quite well.
First, I created the Overall Fleet via aliases for each competitor in the other fleets.
Next, I created the custom rating system “TimePerMile” with the following formulas:
c = e*(a/(r+b))/d This will calculate the corrected time and divide by the distance
e = c/((a/(r+b))/d) This will calculate an elapsed time given the corrected time for the BCE
r = 1/(cd/(ea))-b This will calculate the rating given the elapsed time for the BCR
Next came the challenge of getting the course distances into the aliased Overall fleet. After some pondering, Jon recommended using the “Division” field to effectively create “starts” (Non-Spinnaker, Spinnaker) for the Overall fleet where the course distance could be defined. Since we have 2 Spinnaker starts (faster boats start 5 minutes after the slower boats), this resulted in 6 separate starts for each race (1 Non-Spinnaker, 2 Spinnaker starts and the 3 starts for the Overall fleet):
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The Spinnaker and Non-Spinnaker fleets use the Standard PHRF Time-On-Time rating, but the Overall Fleet uses the TimePerMile rating system to compute the corrected times that are then scored by whatever scoring system (e.g., Appendix A) that is desired.
I used last year’s results to test the Sailwave implementation against the custom excel based system, and the individual night results are essentially the same (The only real difference is that in the excel base system, we gave Race Officer credit as the average of completed races truncated to an integer, and Sailwave currently does not support that.). We are transitioning to Sailwave for this year’s scoring.
Thanks to Jon for his insight and patience in working through the details of making this work. Attached is a master .blw that we plan to use if anyone is interested in doing something similar. Feedback and suggestions are encouraged.
I plan to incorporate NHC in the near future as well as a parallel system to see if the final rankings change.
Tom Owen