In October, the US Sailing Team 49er Squad logged 31 hours in Long Beach and team Henken/Barrows made big strides in the gybing department. Back in September, we identified two gybing techniques - one which prioritizes hitting a high exit angle to get the kite to “pop” quickly while sacrificing speed, and another technique which elongates the turn in the middle of the maneuver, allowing speed to drop, but ultimately causing the kite to fill sooner, and speed to reaccelerate more quickly.
The “question mark” - fast turn - gybe.
The “VMG” - slow turn - gybe.
The maneuver loss for each tells a pretty convincing, and intuitive story of a 10 meter loss for the fast turn, “question mark” gybe, while a smaller 8 meter loss for the slow, “VMG” gybe. If you slow the turn down, and the kite is able to fill closer to the dead-downwind angle, the gybe is ultimately faster. But what about in tactical situations, where you’re trying to escape the “jump” as the front boat, or trying to attack and jump the boat in front of you?
The theory for many teams, is that a faster turn will lose less lateral distance, thus putting you in a better spot tactically in either situation. But looking at the data this is clearly not the case! Looking 12 seconds beyond the start of each gybe, the boat has returned to full speed in both cases, but in the fast turn (the track to the left), so much speed was lost in the middle of the gybe, and it took so much time to get back to full speed, that the final position is almost dead-downwind of the starting position (left of the parallel lines). In contrast, the slow turn gybe (the right-hand track) puts the boat nicely bow out on port, in a position where they would be bow ahead of a boat turning quickly, making them more likely to jump, or defend against the jump depending whether they were the leading or chasing boat.
The takeaway here: slow that turn down, and allow the kite to fill on a low angle before making up-turn.
In October, the 49er squad spent a lot of time racing around a short course, working on boat handling execution, and the improvement numbers from their maneuvers tell the story:
Using the Racing Alpha Reports (Dashboard>Reports), long term trends in boat handling maneuvers can be analyzed to answer the question: “Is our training moving the needle?” In this case, we’re clearly on the right track!
Understanding the Numbers
Each of the data points in this graph represents relative maneuver loss on a give day. In other words, the smaller the number, the less distance you lost on average in each maneuver that day. You’ll notice a lot of negative numbers here, and that’s because our metric is currently optimized to reflect “relative loss”. In other words, -5 meters of loss doesn’t actually mean you gained 5 meters, but it IS 5 meters better than a 0m maneuver. We plan to recalibrate our algorithms to reflect the actual loss on the race course, but for now, you should look at this as a way to measure trends over time. The downward slope of each trajectory (quantified by the negative numbers next to the colored dots on the right side of the legend) are indicative of progress over time. As the team went through the month of October, they lost less and less distance per maneuver on average.
If you have questions about how this is calculated, or why we have chosen to report relative loss metrics at this point in time, we’re happy to discuss it more, so don’t hesitate to reach out!