Despite the Van Isle 360's formidable reputation, Mother Nature threw the Kerkyra's crew a curve. Instead of fighting complex wind patterns and intense waves, during most of the race they encountered a different kind of challenge: virtually no wind at all.
The June 2013 Van Isle 360 turned out to be one of the calmest races of its kind, and the team spent most of their time trying to gather enough of the imperceptible breezes to coax the boat to each leg's finish line-and on many legs that didn't happen until at least 10 minutes after the time limit expired.
“We had some decent periods of wind but the most remarkable thing was how calm it was overall. We had very flat water,” Thistle says. “That was disappointing in a few ways. We were out there to measure motion and there wasn't much. And we were out there to complete race legs, which was hard to do with those light winds.”
All this equipment and nothing to measure? Well, not quite. Even in the lightest breeze and stillest waters a boat experiences motions detectable by IMU measurements.
“We had one night of rough water on the outside coast, and for me it was interesting to look at the measurements of what the boat was actually doing compared to 'gut' feel,” Thistle recalls. “I will not forget my three-hour 'off' shift when I was trying to sleep up in the bow that night. It was the closest I've come to losing my lunch since I was about five years old. I was sharing the bed with two sail bags and a bunch of emergency gear, and I felt like a tomato being tossed with the other ingredients in a salad-sometimes finding myself on top of the gear, sometimes underneath.Tired as I was, I couldn't wait to get out of bed.”
Figure 2 shows what some of the true boat motion looked like that night.
Nonetheless, the long intervals with very little acceleration encountered during the 2013 Van Isle 360 race presented a real challenge for gyro and accelerometer technology. A key difference between the entry-level and high-performance IMUs carried on board the Kerkyra is the drift in gyro bias in low-dynamic conditions. High dynamics allow for alignment of the IMU output, but long periods with relatively small accelerations cause measurement errors to accumulate and create a bias in the output. The sailboat provided good examples of this effect (see Figure 3).
Despite the calm seas, the NovAtel crew not only had a chance to learn about the gear they brought on board, they had to make sure it was running properly and collecting data throughout the race.
The SPAN receivers logged inertial and GNSS measurements that could provide postrace insights for enhancing future performance.
“When you make an adjustment on the boat to improve performance, you're going by feel,” Thistle says. “Part of my interest in it was to see if you could bear out in the data what you felt you were doing to improve the performance of the boat. This made me realize some of these fine tunings may have made improvements, but that's very hard to measure with all the motion going on in boat and all the variables. It's hard to separate those different factors.”
The position data they obtained gave an accurate record of their route, providing the type of detail that Thistle and the rest of the crew agree would be valuable training data if presented in near real-time.
“I had some ideas about [real-time tracking in this race] but had enough to prepare without it,” Thistle says. “Even now, after looking at the data, I can see it would take more thought to figure out what is the best information to provide in real time and what is the best way to present it.”
The team at NovAtel considers the experiment a success. “There is a wealth of good measurement data from this equipment,” Thistle says. “I can see how it might be combined with wind and sail trim information and 'mined' to draw more conclusions about how best to sail a boat. This would take a lot more work, but some racing programs spend millions of dollars to optimize their boats and crews.” He adds, “It's important for companies to encourage people to try things like this. It's not really a failure if you go looking for something and you don't find it. It's all learning. We had some ideas but, in general, we said, 'let's go out and study this motion and capture it.'”
Even though Mother Nature changed the race dynamics, they learned a lot about each other during the process, and worked as a true team as they debated how to fill those sails, fix broken equipment, and solve various challenges that came up along the way. The team element is one of Thistle's favorite aspects of sailing, and he loves the interaction and ideas that come into play as they face each challenge.
Aside from all the technology, how did they do in the race? “We had a great time,” Thistle says with a smile. “We didn't really keep track of who won. But if there was a prize for best instruments or biggest fish...”
The next Van Isle 360 is slated for June 2015, and Thistle hasn't ruled out the idea of entering it. He tries to enter one race a year, and the thought of tackling those high winds and rough seas may lure him back yet again.