Correcting sailing times for handicap races

Correcting the sailing time.

It takes a few steps to get from a boat's recorded sailing time to the eventual corrected time.

First we have to make sure we are using the right measured sailing time.

In a simple case, we just read the time off the stopwatch, and that is the official sailing time. But what if we had a split start? The watch will have started at zero for the first of the starts, but will have been counting up the minutes before any later start, so we need to subtract the difference, for later starters, to arrive at the actual sailing time. (This only applies to scheduled later starts; we don't make any allowance for people who didn't get to the starting area in time.)

And not all boats will have sailed the same number of laps. For the ones that have sailed a smaller number, we need to scale up their time, to arrive at what it would have been if they had sailed the full number of laps. We divide by the actual number of laps completed, and multiply by the full number. At last we have the effective elapsed time for each boat.

Finally we have to make a correction for the handicap number. For each boat, we divide the elapsed time by the boat's handicap number, and multiply by 1000.

The full formula is

    (Finish time - Start time ) * (Full lap count)/(completed lap count) * (1000 / class PN).

This gives us a standardised time, known as the "corrected time", and it is these corrected times that we compare to find out everyone's position.

The sign-on and results sheet has spaces to allow for the recording of each of these stages. We aim to fill them in immediately after the race, using the ready reckoner tables in the Race Officer Handbook. (Some people prefer to use a calculator to get the same effect.) Either way, the sailors have a provisional indication of their result. But the official result comes later, when all the figures are fed into the Sailwave programme, and published on the website.