Empirical Handicapping Conversion Formulae
There are a number of other handicapping systems that can be useful information when looking at empirical handicaps. Although none of these can be expected to be identical to PHRF, they are useful for determining if you are in the "ballpark". Here are several conversions for going from one handicapping system to another.
IRC: The RORC web site recommends a conversion factor to Time on Distance of 600/IRC. However, the following formula seems to give better results:
PHRF = (650/IRC) - 557
IMS: The IMS General Purpose (GPH) number can be useful. You have to keep in mind that IMS does not do a great job of handicapping boats that are not designed to the latest version of the rule. The most common conversion is:
PHRF = IMS GPH - 550
The 550 factor should perhaps be decreased a little if the boat is an older one and increased a little if the boat is a state of the art racing machine. Another conversion, determined by Nils Nordenstrom of Norway is:
PHRF = - 480 + 0.9 * IMS GPH
The accuracy of these can vary from year to year as the IMS rule changes. For boats not designed to the rule this can give answers that 10 to 10 Seconds per Mile, and more, in error. The error is usually to over estimate the speed. Some sprit boats are prime examples of this error. Ligh displacement boats also tend to be severly handicapped by IMS.
Dixie Portsmouth: The PHRF conversion from the Dixie Portsmouth system used in the United States is:
PHRF = 6 * DPN - 330
ASPN: The Atlantic Speed Potential Number is a Time on Time factor used by the Nova Scotia PHRF. The following is the relationship to PHRF Time on Distance:
PHRF = (63000/ASPN) - 400
Argentine PHRF: The Argentine PHRF handicap is given in feet, as the IOR was. Converting to PHRF Time on Distance is similar to converting from the IOR itself. The conversion into a Time Correction Factor is:
TCF = (2.6 * R)/10
HN: Handicap National is the empirical system used in France
PHRF = 0.88 * HN + 99
LYS: The LYS system is a Time on Time system used in the Nordic countries. The conversion to PHRF is:
PHRF = - 480 + 720/LYS
The LYS handicap itself can be related to the IMS by:
LYS = 800/IMS GPH
The LYS handicap can be related to the ORC TCF by:
LYS = 600/ORC TCF
ECHO: This is the "personal" handicapping system used in Ireland. Basically they start out with an empirically derived base number. Then a crew factor is applied. This system also has a "Jockey Factor". For instance, if you import a ringer for a regatta, your handicap will be adjusted accordingly.
The time correction factor can be reasonably converted using the standard formula.
PHRF = (600/ECHO) - 500
IOR: The International Offshore Rule presents a difficult conversion problem. Being a very type forming rule, conversion is very sensitive to when the boat was designed. For boats not designed to any version of the rule, all bets are off. The formulae shown here attempt to represent the extremes, early and late, of IOR designs.
Early IOR Conversion: PHRF = - 9.7 * R + 384.9
Late IOR Conversion: PHRF = - 10.8 * R + 379.8
The actual PHRF handicap "should" be somewhere between the two numbers generated above.
Time-on-Time: Time-on-Time scoring can help, over Time-on-Distance scoring if there are unusual race conditions.