All your essential start data on SailViewer’s Start screen.
By using the SailViewer app, you can quickly access key start line data that matters. Based on insights from hundreds of races analyzed through SailViewer’s race reports, we’ve gathered a few tips to help you make the most of your starts.
Long vs Short lines
Long Lines, Big Differences
A long start line can create a significant bias, even when the wind is only a few degrees off square. A useful reference number is 6° of bias, which results in a 10% upwind advantage over the total line length. For example, on a 450-meter start line, that’s a 45-meter upwind difference between the two ends.
In most racing classes, sailors fight for every single meter—and giving up 45 meters right from the start is incredibly hard to recover. That’s why, when dealing with a long line, the priority should always be to leverage the bias as soon as it becomes visible.
In many cases, it’s better to have an average start at the favored end than a perfect start at the unfavored one. The gap you’d need to close is just too big. (Though, as we’ll explain further below, there are a few exceptions.)
When a Clean Start Beats the Favored End
On a shorter start line, the upwind difference between the ends is much smaller. In these situations, starting slightly away from the favored end crowd—where you can get off the line cleanly—can actually be more effective.
When boats are stacked tightly near the favored end, they often pinch hard and slow each other down. Meanwhile, if you’re just a bit clear of that traffic and able to sail fast in clean air, you can make up those few meters quickly.
In this case, speed and freedom can outweigh the small positional loss from not being right at the biased end.
When the Bias is Temporary: Playing the Shifts at the Start
Sometimes you’ll notice clear start line bias, but you know it’s caused by a temporary wind shift—not a permanent one. In that case, there’s a high chance it will cancel out shortly after the start, or even just before the gun.
To make this call confidently, you need to have a good understanding of the typical wind range before the race—knowing the average and max values for both left and right shifts. If the wind has been consistently oscillating and there’s no expectation of a lasting trend, you can use those numbers to your advantage.
In these conditions, your main goal should be to start in a position where you can sail the lifted tack off the line:
• If the wind is currently right, give yourself enough leeward space to avoid being pinned and forced to tack.
• If it’s left, try to position yourself so you can tack onto port early, or even consider a port-tack start if clear lanes allow.
Keep in mind the relationship between the shift and the bias:
• If the observed bias is larger than the shift, then it’s not only the shift causing the bias—there’s also real line angle bias.
• In that case, you still want to start at the favored end, since the wind shift reversing won’t fully cancel out the advantage.
Start Smarter with SailViewer
Understanding start line bias, wind shifts, and how to position yourself accordingly is a game-changer—especially when decisions are measured in meters. Whether you’re racing on a long or short line, in stable or shifting breeze, your ability to read the situation and learn from it can make all the difference.
That’s where SailViewer comes in. By providing clear post-race analysis of start line angles, distances, wind behavior, and boat positioning, the app helps you turn every session into a learning opportunity. Built from the insights of hundreds of top-level races, SailViewer gives you the tools to refine your strategy, recognize patterns, and line up smarter in the next race.
Download SailViewer and start lining up with better decisions, not just instinct.