Winning the Rulebook: How Emirates Team New Zealand Redefined AC75 Power
Strategic Overview: The Fight for Righting Moment
In the high-stakes world of the , the battle isn't just fought on the water; it is won in the design office. (ETNZ) has executed a masterclass in rule interpretation by identifying a critical loophole regarding mast rotation. While the class rules fix the height of the mast ball rotation point relative to the foils, ETNZ realized the rules say nothing about the height of the deck surrounding that point. By lowering the deck and placing the mast on a plinth, they’ve essentially dropped the entire rig, gaining 18 inches of effective sail area in the most powerful zone of the boat.
Performance Breakdown: The Boomless Compromise
This lowering of the rig forced a radical departure in mainsheet geometry. Unlike the sleek, under-deck systems seen on , ETNZ utilizes a "clunky" boomless setup where the hydraulics sit directly within the sail's clew. To a casual observer, the fattened clew and exposed rams look agricultural and inefficient. However, the tactical advantage is undeniable. This configuration allows for a ball-and-socket joint that permits the sail skins to articulate independently, accommodating massive mast rotation and providing vertical play that acts as an automatic adjustment system for the trimmers.
Critical Innovation: The Upper Control Zone
At the top of the rig, the four-meter "Upper Control Zone" has become a laboratory for mental resilience and technical execution. initially experimented with heavy articulating booms to force sail shape, but found the weight penalty too high. The winning strategy has shifted toward tension-based manipulation. By adjusting lines connected to opposite skins, teams can now "pop" battens to invert the top of the sail. This creates drag but massively increases the righting moment, allowing the boat to carry immense power through the lower sections without capsizing the platform.
Future Implications: The Batwing Evolution
We are now seeing the emergence of "batwing" sails—a direct result of teams looking to shed sail area high up without the drag of an inverted profile. By cutting chunks out of the sail between battens, designers reduce the center of effort while staying within minimum size requirements. This trade-off between upwind drag reduction and downwind power will define the next generation of foiling tactics. ETNZ has proven that the team that unpicks the rulebook with the most courage is the team that dictates the pace of the game.
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America's Cup Mainsails: Another ETNZ Loophole! + Mysterious Upper Control Zone
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