Design


Extreme H2O: Designing the PB72, a semi-foiling


offshore machine


Ferdinand vanWest, project lead designer atMorrelli&Melvintakesus through thenaval architecture of ExtremeH20, the PB72, a semi-foiling offshoremachine


E


very now and then, a yacht begins not with a design brief, but with a question. In the case of the PB72, it started in the middle of the Pacific Ocean.


During the 2015 Transpac Race, a legendary offshore sprint from Los Angeles to Honolulu, known for its fast passages and trade wind surfing. But for Patrick Benz, owner and sailor of a Gunboat 66, that particular race became more than just a performance benchmark. That race, and the hundreds of hours of performance sailing that preceded it, planted a vision in Pat’s mind – one that would evolve into one of the most technically ambitious multihulls we've ever developed at Morrelli & Melvin. Midway through the race, flying


downwind aboard his sleek catamaran, Pat was struck by the limitations of the foiling systems then in use. The C-shaped foils on his Gunboat offered lift, sure—but they were inherently a compromise. The


78 SEAHORSE


curved design generated both vertical lift and lateral force at once, a coupling that made control more complex. What if, he wondered, those forces could be separated? What if you could decouple lift and leeway resistance, and do it all on a luxury cat designed not only to race, but also to live on? That question echoed through the


years that followed. It became a design brief, then a mission. And ultimately it became the PB72 – a 72ft semi-foiling performance catamaran that pushes beyond the boundaries of conventional multihull design.


Reimagining performance From the outset, the PB72 was never meant to be an iteration. At Morrelli & Melvin, we approached this project as a clean-slate opportunity to explore what’s possible when high-performance design tools, advanced hydrofoil systems and offshore capability all converge. Our


objective wasn’t to create a full-foiling machine suited only to narrow wind bands. It was to develop a next-generation platform capable of sustained, high-speed sailing in the real world. A major step forward came in the


foil configuration. Traditional curved daggerboards like those we used on earlier performance catamarans provide both lift and lateral resistance – but by combining those forces into a single element, you sacrifice precision and control. With the PB72 we opted to separate the tasks: straight high-aspect daggerboards handle leeway resistance; T-rudder foils with elevators manage pitch and directional stability; and the righting moment foils (RMFoils) generate vertical lift and massive righting moment – up to 180 per cent more – allowing the yacht to ride higher and faster while staying firmly under control. This setup allows the PB72 to operate in a semi-foiling mode, optimised for


PERSICO MARINE


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