Scoring a Race with the Portsmouth System

When you read the Cherry Blossom Notice of Regatta (NOR), you might have noticed a line that said, “Racers times will be adjusted for boat differences using the Portsmouth system.” That means, first of all, that you can’t always tell who won the race just by watching who crosses the finish line first. But more importantly, it means that even a slower boat has a fair chance of winning against a faster boat if the skipper of the slow boat sails a better race. Different sailboat designs have different speed potential around a racecourse and without a handicap system like Portsmouth, the skipper who went out and bought the fastest boat would usually win the race and it wouldn’t be much fun for anyone else. This way, at least in theory, everyone stands a chance.

The Portsmouth system, officially the “North American Portsmouth Yardstick”, was developed and is maintained by US Sailing – the governing body of sailboat racing in the United States. Each year many thousands of actual race results from around the country are statistically analyzed and the ratings are mathematically adjusted to reflect the actual observed performance differences among different models of boats. The process and results are posted on the US Sailing web site at http://www.ussailing.org/Portsmouth.

To score a race using Portsmouth, first you look up the handicap factor, called the D-PN, for each boat in Portsmouth ratings book, or on the web site. At the finish line you record the elapsed time for each racer and then apply the correction factor using the simple formula (Corrected_Time = Elapsed_Time * 100 / D-PN). A smaller D-PN indicates a faster boat and the rating number essentially tells you what percentage faster, or slower, a particular boat is relative to a baseline boat rated at 100. For example, a boat with a DPN of 90 who finishes a race in 60 minutes will get a corrected time of 66.67, and a boat with a rating of 95 who finishes in 63 minutes will get a corrected time of 66.32. The slower boat wins this race even though he crossed the finish line three minutes later!

The PHRF Handicap System

For dinghies and daysailers, the Portsmouth system is most likely the only one you will ever see, but if you sail a keelboat or cruiser and travel to other regattas you will probably also encounter the PHRF system. There are some fundamental differences between Portsmouth and PHRF. First of all, the rating numbers are derived differently. While the Portsmouth rating numbers are determined by statistical analysis of actual race performance, the PHRF numbers are determined by local committees who assign a number to each boat design that sails in their region. Both approaches have their problems and you have to decide for yourself if you prefer the problems of statistics or the problems of committee politics. Secondly, most PHRF races are scored “Time-on-Distance” while Portsmouth races are always scored “Time-on-Time” (as described above). In order to score a race Time-on-Distance, you need to know the exact length of the racecourse in addition to the elapsed time and rating of each boat. The formula for PHRF is Corrected_Time = Elapsed_Time - (Race_Distance * PHRF) / 60. The need to know the exact distance around the course makes Time-on-Distance difficult to use for racing around temporary buoys and hence the reason that dinghies usually race under the Portsmouth system.

One-Design Racing

No matter how well a handicap system is designed, there will be situations where it is unfair to some boat or another. If all the racing boats have very close ratings and similar sizes and weights, then the unfairness tends to be very small, but when the boats have widely varying ratings and speeds, the unfairness can be large. It’s all just part of the game when racing in a handicap fleet, but there is an alternative. When all of the boats racing against each other are the same, there is no need for a handicap system at all. The first boat over the finish line wins and there is no need for any kind of corrections. In fact, you don’t even need to measure elapsed time – just write down the sail numbers as the boats cross the line and post the results when you get back to the dock. In one-design racing you have no excuses. The playing field is level and your sailing makes (almost) all the difference. But every system has it’s downside – in this case everyone has to buy the same kind of boat and if you do more than just race your boat, that can be a little too restrictive.

Scoring a Regatta

Once you have scored each individual race in a regatta, the Racing Rules of Sailing (RRS) provide two methods for adding the scores together to determine an overall winner. LJSC uses the “Low Point System” with either all races counted, or the worst score discarded. Whether or not the worst score will be discarded is listed in the “Sailing Instructions” (SI) given out at the skippers meeting. For each race, each boat is given points according to their finish place in the race, with first place getting one point, second place getting two points and so forth. The points are added together and the boat with the lowest score wins. Ties are resolved in favor of the boat that finished ahead of the other more often based on a complicated process defined in the RRS. A boat that either Did Not Start (DNS), Did Not Finish (DNF), or was Disqualified (DSQ) is given a score one point higher than the total number of boats entered in the regatta.

Scoring a Series

A “Regatta” is usually considered a series of races held on one day or consecutive days at a single location. There are a few special rules for scoring a series of races longer than a single regatta, such as a club championship. In that case a boat that came to a particular race, but got a DNS, DNF, or DSQ is given only one point more than the number of boats that actually started that particular race. A boat that did not attend the race at all is given one point more than the total number of boats that raced at any time in the series. This gives a big bonus to the sailors that make the effort to show up for more races.

Race Results

As the club races are completed this year and the results on computed, we will post the full results on the Rudder web site with elapsed times and corrections for each individual race that was held on a particular day. This way you can see for yourself how the system works and exactly why one boat may have finished higher than another at the end of the day.