Design & Technology · Naval architecture

Fat birds
don’t fly

It was the first rule Morrelli & Melvin gave the project. Every line of PB72 still answers to it.

“What if we tried this again? … Just start from scratch.”

Dr. Pat Benz · On the dinner that started PB72

The designers

Morrelli
& Melvin

From Newport Beach, California, Gino Morrelli and Pete Melvin have drawn America’s Cup yachts and many of the fastest catamarans ever built. They also designed the original Extreme H2O.

For PB72 they had something rare: a client with a decade of data from his previous boat, a willingness to start over, and a scientist’s appetite for simulation. The brief was not a faster version of the old boat. It was the boat the old one pointed to.

The engineer on PB72 is Ferdinand van West, who worked with Pat and Pete Melvin from the first conversation in Sarasota to the final general arrangement.

Morrelli & Melvin
Dr. Pat Benz explaining PB72 at the design boards

Proportion

Proper proportions
of hull and rig

To balance the boat for speed and keep the same saloon as the original, she had to grow to 72 feet, with a waterline close to her full length, a wider beam, and the mast moved back to the top of the cabin roof. Below foiling speed, a boat is fastest when her full length is in the water, so the hulls were proportioned to keep a full-length waterline at low speed; once she is on the foil, that no longer matters. Comfort was never allowed to dictate shape. The hulls stay long and fine; the cabin sits low and well aft, its roof doubling as the base for the boom so the mainsail sheets straight down onto the structure.

Computational flow visualisation of air moving over PB72’s hulls, cabin, beams and rig

Aerodynamics

Shaped
by the air

The cabin front is shaped like an aircraft windscreen. At foiling speed the apparent wind can top forty knots, and every square metre of frontal area costs speed.

So the air was modelled as carefully as the water. Computational flow simulations traced how it moves over the hulls, cabin, beams and rig.

Designed in simulation

A digital
ocean

“Designing a yacht like this requires you to sling out the textbook. The concepts don’t exist in old drawings or handed-down rules of thumb.”

Ferdinand van West · Seahorse, July 2025

PB72 sailing downwind in the Gomboc simulator, with helm targets and foil data on screen

Gomboc · Dynamic VPP

PB72 was sailed thousands of times before she was built, in Gomboc, the dynamic velocity-prediction program developed by SumToZero and used by Emirates Team New Zealand. Foil shapes, hull shapes and sail configurations were tested and refined in simulated wind and waves.

CFD visualisation of water flowing around PB72’s hull, righting-moment foil and rudders

CFD · Hydroflow

A CFD simulation of PB72 semi-foiling upwind at a predicted 26 knots, showing how the water moves around the hull, the righting-moment foil and the rudders. Upwind foiling is still to be tested in sea trials.

“Four giant hydraulic winches… each one can hold like twelve tons.”

Dr. Pat Benz · On the sail controls

Deck layout

Everything
led aft

Halyards come down the mast and run through tunnels in the cabin roof to a stand behind it. Every sheet comes to one of four hydraulic winches, two each side. The result is a 72-foot catamaran that a crew of four on each watch can sail fast, and nobody has to go forward at thirty-five knots.

Rig

A 32-metre
carbon mast

Mast tube
32.33 m
4° design rake
Mainsail
224 m²
Three reefs
J1
196 m²
A1 gennaker
365 m²
Air draft
37 m

The drawings

Side and
front views

The rig towers over two slender hulls; from the front, the curved foil reaches out to leeward. Click either drawing to see it full screen.

Drawing PDF
PB72 side view: hull, 32.3 m rig, sail plan, foil and rudder, with principal dimensions
Side view · looking to starboard
PB72 front view: both hulls, the rig and the curved lime foil deployed to leeward
Front view · looking aft

Morrelli & Melvin Design & Engineering · PB72_001 Rev A · 6 August 2022 · Reproduced with permission

NextFoils & flight control

Private enquiries

PB72 is in sea trials. Partnerships, racing programs, experiences and charter are discussed personally with our team.