Appendix A. DYNAMIC HANDICAPPING

A sailboat rating system allows divergent boats to race competitively. Dynamic Handicapping is a boat rating system that periodically re-adjusts each boat's handicap based on its recent finishes. In the early 2000's, US Sailing proposed using a golf-like handicapping system for open-fleet racing, and suggested a system which would adjust all corrected times to that of a reference finisher within the fleet. An expedient approach toward such a goal requires use of a Time-on-Time technique.

In Time-on-Time handicapping, a boat's rating value is expressed as a Time Correction Factor (TCF). The standard US Sailing formula for converting a PHRF seconds-per-mile allowance into TCF is:
            TCF = 650 / (550 + PHRF)

For a given race:

• 1. A boat's Corrected-Time (CT) is its Elapsed-Time (ET) multiplied by its TCF:
              CT = ET * TCF

• 2. Results for one race are calculated and ordered by CT and the boat having the lowest CT is the winner.

• 3. The boat exactly in the middle of the fleet (median) based on CT is the ‘Mark Boat’ (reference finisher) and its CT is the Median-Corrected-Time (MCT).

• 4. For each boat, its New-TCF (NTCF) is calculated:
  

  • a. An Equalizer-Rating is calculated by dividing each boat's ET into the MCT of the Mark Boat: ER = MCT / ET
  • b. (To remove outliers, ER is ‘clamped’ to within 1.5 standard deviations (sigma) of fleets TCF set.)
  • c. The NTCF is the Equalizer-Rating weighted by past results.

• 5. The NewTCF rating will be used for the next race.

The final formula: NewTCF = ((MCT / ET) + 2 * TCF) / 3

This dynamic handicap concept is used widely in Australia, and this specific formula originated from the Royal Sydney Yacht Squadron. The concept is called PHS (Performance Handicap System) and is published by a few Australian scoring programs such as SailSys and TopYacht.

TopYacht's detailed (complex) write-up can be found at: Calculating New Handicap

A local copy of the TopYacht document is here: Next Handicap