In a class championship of 40 boats, the race committee sets a starting line that is about 40 boatlengths long. When you go head to wind in the middle of this line, you notice that the committee boat (starboard) end of the line is favored by 10 degrees. In other words, the wind direction is 10 degrees to the right of the direction that would make the line perfectly square. While planning your first-leg strategy, you wonder how much of an advantage you would get by starting at the committee boat end. QUESTION: If a boat starts on starboard tack right at the committee boat end, how far ahead will she cross in front of a boat that starts at the pin end on port tack?
Correct Answer: 10 boatlengths
Explanation : By using a little geometry (I won’t go into the calculations here), we find that every 5° of bias in the starting line produces an advantage (or disadvantage) of about 12% of the length of the starting line. For example, if the starting line is 100 meters long and the pin end is farther upwind by 5°, a boat that starts at the pin end will be roughly 12 meters ahead (100 x 10%) of a boat that starts at the committee boat end. Or, in the diagram here, the starting line is 40 boatlengths long and the boat end is farther upwind by 10°. This means if you start near the committee boat you will already be about 10 boatlengths (40 x 24%) ahead of a boat that starts near the pin end. It's important to have some accurate idea about this number since this is the distance you will be gaining by starting at the upwind end, or giving up by starting at the end that's not upwind.