In July, OTUSA was not able to do foiling gybes as consistently as Team New Zealand. They were losing about 150 meters on their “good” gybes, and they felt they needed to get that down to about 30 meters. By early August, their engineers had developed a new foil control system that allowed them to gybe smoothly.
Using a “mechanical feedback loop” helmsman Jimmy Spithill was able to change the angle of the daggerboards in increments of 0.5° giving dramatically more stable foiling.
Lots more details and marked up photos and diagrams here.
Mounting the hydraulic valve on the movable daggerboard box, and the servo that controlled it on the fixed part of the boat allowed the helmsman to adjust the boards very precisely. More info here.
Each press on the buttons changed the daggerboard rake by 0.5° – precise control for stable hydrofoiling.