Time-on-time vs. Time-on-distance

There are two main types of scoring systems: time-on-time (ToT) and time-on-distance (ToD). These two systems are very similar, but there are some key differences. One advantage to ToD is that you can tell your standing at any point in the race but ToT helps boats with a wider range of speeds and sizes.

More about ToT

The most commonly used scoring system for handicap sailing today is still PHRF. PHRF is primarily a time-on-distance handicap system, with ratings being in the unit seconds per mile. Ultimately, ToT scoring is a way to convert a boat's elapsed time to a corrected time, to do that, we must calculate each boat's time-correction-factor (TCF). The TCF is multiplied by the elapsed time to get the corrected time. Or, in math form.

$$TCF = \frac{A}{B + PHRF}$$ $$A = \text{Fleet Coefficient}$$ $$B = \text{Condition factor}$$

Variable B is a condition factor that is used to adjust the TCF for the conditions. The lower the B factor, the heavier the wind, or the more downwind sailing the course demands. This means that less time is allotted to each boat sailing the course. These numbers change from fleet-to-fleet but a good rule of thumb is to use 600 for a light wind or all upwind, 550 for average conditions, and 475 for heavy-air, or all downwind sailing.

The denominator, B + PHRF, is the number of seconds it takes to sail a nautical mile in the expected conditions. To calculate average boatspeed, we use the following formula.

$$BSP = \frac{3600}{B + PHRF}$$

Try it out:

The numerator A, is simply a coefficient that makes a "nice" looking TCF. Select it so that the TCF for the middle of the fleet is about 1. RegattaPages.com has a nice calculator for this below, and built into the regatta admin interface. If your median handicap is about 100 and the conditions are average, then the TCF formula would look like the following.

$$TCF = \frac{650}{550 + PHRF}$$