Design & Technology
An aircraft’s logic,
a sailor’s sea
PB72 was approached as an aerodynamics problem: lift, drag, weight and control. Every answer is in the water, the rig or the carbon.
The idea
From 30% lift
to full flight
The original Extreme H2O’s C-foil carried about 30% of her weight at 23 to 25 knots, and any faster it pulled the boat to windward. Pat Benz wanted to know what would happen if the same idea were designed in from the start, on a bigger, lighter, stiffer boat, with nothing inherited.
Morrelli & Melvin started from a clean sheet. Thousands of velocity-prediction runs later, the answer was a 72-foot catamaran with a single, enormous lifting foil per side, independent daggerboards for leeway, raking T-foil rudders for pitch, and a flight-control system designed to manage it all once it is programmed after sea trials.
Then they took the weight out of everything else.
- Lifting foil
- 16 × 3 ft
- Curved carbon, hydraulic rake
- Foils per side
- 2
- Lift foil + daggerboard
- Hydraulic winches
- 4
- ≈ 12 t working load each
- Foiling from
- 11 kn
- True wind speed
- Predicted top speed
- 40+ kn
- Polar peak 40.7 kn
Designed in simulation
Flying
before she
floated
Before a single part was laminated, PB72 had sailed thousands of virtual miles. Morrelli & Melvin and North Sails “sailed” her in a six-degree-of-freedom simulation, starting at a 50% lift fraction, which everyone but Pat thought was the limit for control. Each step up was costly to run, but the boat stayed stable at 90% and then at 100%.
The coloured lines here trace the water as it streams off the foil: the same physics that now lifts the real boat.
“The foil that can lift this entire boat out of the water is about three feet wide and sixteen feet long.”
Inside the engineering
Four disciplines,
one yacht
- Naval architectureMorrelli & Melvin’s clean-sheet design, proportions and rig.
- Foils & flight controlThe righting-moment foil, T-foil rudders and fly-by-wire control.
- Structure & materialsCarbon over foam and Nomex, weighed to the gram, ISO Category A.
- Performance dataPolar speeds, foiling onset and what twice the wind feels like.
The drawings
Side and
front views
Morrelli & Melvin’s general arrangement: the full rig and sail plan from the side, and the curved foil reaching out to leeward from the front. Click either drawing to see it full screen.
Morrelli & Melvin Design & Engineering · PB72_001 Rev A · 6 August 2022 · Reproduced with permission
Lift the hull,
lose the drag
The foil beneath the surface
Private enquiries
PB72 is in sea trials. Partnerships, racing programs, experiences and charter are discussed personally with our team.
Extreme H2O · Foiling ocean catamaran · Technical specification
PB72 specifications
Morrelli & Melvin · GA PB72_001 Rev A · Persico Marine build spec
- Length overall
- 21.95 m
- 72.0 ft
- Beam
- 9.50 m
- 31.2 ft
- Racing displacement
- ≈ 21.5 t
- As built · VPP targets at 20.3 t
- Mast
- 32.33 m
- Air draft 37 m
- Upwind sail area
- 420 m²
- Main 224 + J1 196
- Fastest upwind
- J3 + main
- Full main 224 + J3 115 m²
- Fastest downwind
- MHO + main
- Full main 224 + MHO 358 m²
- Predicted top speed
- 40+ kn
- VPP
Principal dimensions
- Length overall
- 21.95 m72.0 ft
- Length incl. longeron
- 24.10 m79.1 ft
- Length waterline
- 21.45 m70.4 ft
- Beam overall
- 9.50 m31.2 ft
- Hull centreline spacing
- 7.52 m24.7 ft
- Freeboard
- 2.07 m6.8 ft
- Draft, boards down
- 5.31 m17.4 ft
- Draft, foils raised
- 0.65 m2.1 ft
- Air draft
- 37.00 m121.4 ft
Displacement & stability
- Light displacement
- ≈ 21,000 kgAs built · design 20,500 kg
- Racing displacement
- ≈ 21,500 kgAs built · as sailed in sea trials
- VPP target displacement
- 20,280 kgDesign racing weight used for the polar targets
- Design displacement (mLDC)
- 23,047 kgMaximum load condition
- Max total load (ISO 8666)
- 22,518 kg
- Steady-state sailing RM
- 830 kNmAt full-payload displacement
- Max dynamic RM
- 1,340 kNmRace mode, RMFoil deployed
Rig
- Mast tube length
- 32.33 m106.1 ft
- Mast design rake
- 4°
- P
- 31.285 mReefs: 26.604 · 21.970 · 14.190 m
- E
- 9.678 m
- I (1 · 2 · 3)
- 33.470 · 32.775 · 30.900 m
- I headstay (5 · 6)
- 28.050 · 25.720 m
- J (1 · 2 · 3)
- 12.180 · 11.730 · 10.980 m
- J headstay (5 · 6)
- 8.744 · 8.072 m
- BAD · HBI
- 1.906 · 2.019 m
Sail areas
- Mainsail, full
- 224 m²Reefs: 183 · 144 · 76.8 m²
- J0
- 219 m²
- J1
- 196 m²
- J3
- 115 m²
- J4 / staysail
- 87.3 m²
- FRO
- 304 m²
- MHO
- 358 m²
- A1
- 365 m²
- Fastest upwind setup
- J3 + full mainJ1 in marginal upwind conditions, 13–14 kn: partial foiling
- Fastest downwind setup
- MHO + full main
Foils & flight control
- Righting-moment foil
- ≈ 16 × 3 ftCurved carbon foil in a hydraulically raked case
- Daggerboards
- Centreline, per hullIndependent of the lifting foil
- Rudders
- Raking, T-foilConical titanium bearings · ≈ 6 ft T-foils
- Flight control
- Designed for fly-by-wireFoil lift and rudder-elevator control; programmed after sea trials
Construction & class
- Hull
- Carbon fibreFoam & Nomex sandwich
- Superstructure
- Carbon fibreFoam & Nomex sandwich
- Classification
- ISO 12215-7 Cat. ASER1 multihull · highest category, sport boat
- Propulsion
- 2 × 35 kW electricTorqeedo
Rig & deck hardware
- Mast
- Carbon rotating wing mastSupplied by SSNZ · single spreader, double diamond, running backstays
- Primary winches
- 4 × Harken 1125.3
- Secondary winches
- 2 × Harken 65.3 ST
- Windlass
- Lewmar V6 hydraulic
Propulsion & power
- Main engines
- 2 × Torqeedo electric25 kW continuous · 35 kW max each
- Drive
- Shaft driveStrut and P-bracket · Gori GP20 folding propellers
- Motoring speed
- 9.2 kn max7.5 kn cruise (estimated)
- Generators
- 2 × 20 kW Fischer Panda
- Propulsion battery
- 40 kWh lithium-ionBMW i3 cells
- Solar
- 2 kWPanels on the coachroof
- Electrical
- 120 V and 240 V AC400 V DC charging & hydraulic bus · 24 V domestic · Empirbus digital switching
Tankage
- Fuel
- 2 × 550 L
- Fresh water
- 2 × 450 LPlus 70 L drinking water
- Watermaker
- Schenker Modular Zen 50
- Black water
- 2 × 220 L
Comfort & systems
- Air conditioning
- 64,000 BTU/hTermodinamica
- Galley
- Gaggenau hobsPizza oven · Miele microwave · Miele coffee machine
- Refrigeration
- 3 × 172 L fridgesPlus Frigonautica freezer
- Navigation
- B&G / Simrad
- Communications
- VHF · 5G · SatcomSatellite broadband
- Steering
- Outside helms + inside helmFly-by-wire steering at the inside helm station
Performance
- Predicted top speed
- 40+ knPolar peak 40.7 kn
- Foiling onset
- 11–13 kn TWSDepending on sail set
- Upwind, 13 kn of wind
- ≈ 24 kn
- Downwind, 14 kn of wind
- ≈ 31 kn
- Crew
- 4 per watchTo sail her fast; two watches for round-the-clock ocean racing
Velocity prediction program, partially validated in sea trials.
Design & build
- Naval architecture
- Morrelli & MelvinNewport Beach, California
- Lead designer
- Ferdinand van WestThen at Morrelli & Melvin; now Van West Naval Architecture
- Interior architecture
- Design Unlimited
- Builder
- Persico MarineItaly
- Flight control
- Team New Zealand engineers
- General arrangement
- PB72_001 · Rev A6 August 2022
Figures from the Morrelli & Melvin general arrangement (PB72_001, Rev A, August 2022) and the Persico Marine build specification. Displacements are approximate as-built figures from Ferdinand van West (2026); righting moments are design estimates; performance figures are VPP predictions, calculated at the 20,280 kg design racing displacement.
Every cell is a predicted boat speed from the velocity prediction program. The circled cells are the targets PB72 has already hit in her first sea trials, with the foils still trimmed by hand. Each one came in on target.
| Wind angleTrue wind (kn) | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 18 | 20 | 22 | 24 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 45° | 7.6 | 8.4 | 9.1 | 9.8 | 10.4 | 11.3 | 12.6 | 13.6 | 14.4 | 15.1 | 16.0 | 17.4 | 20.5 | 23.4 | 24.0 | 23.7 |
| 50° | 8.0 | 8.9 | 9.7 | 10.5 | 11.2 | 12.8 | 14.3 | 15.1 | 16.3 | 17.6 | 19.5 | 21.6 | 27.1 | 27.5 | 27.0 | 26.5 |
| 55° | 8.4 | 9.3 | 10.2 | 11.2 | 12.2 | 14.2 | 15.7 | 17.0 | 18.8 | 20.8 | 23.4 | 27.6 | 30.1 | 30.2 | 29.5 | 28.9 |
| 60° | 8.8 | 9.7 | 10.7 | 11.8 | 13.2 | 15.3 | 17.1 | 19.3 | 21.5 | 26.1 | 28.6 | 30.2 | 32.4 | 32.3 | 31.6 | 30.9 |
| 65° | 9.1 | 10.1 | 11.2 | 12.3 | 14.3 | 16.4 | 19.1 | 21.5 | 26.1 | 29.0 | 30.8 | 32.2 | 34.3 | 34.2 | 33.4 | 32.4 |
| 70° | 9.3 | 10.4 | 11.5 | 12.7 | 14.9 | 17.9 | 20.9 | 24.1 | 28.6 | 30.8 | 32.4 | 33.8 | 35.8 | 35.7 | 34.8 | 32.3 |
| 75° | 9.5 | 10.6 | 11.8 | 13.1 | 15.4 | 19.4 | 22.6 | 27.3 | 30.2 | 32.2 | 33.7 | 35.1 | 37.1 | 37.1 | 36.2 | 34.0 |
| 80° | 9.7 | 11.0 | 12.3 | 13.9 | 15.8 | 20.6 | 25.1 | 28.7 | 31.4 | 33.2 | 34.7 | 36.1 | 38.1 | 38.2 | 37.3 | 36.2 |
| 85° | 9.8 | 11.2 | 12.6 | 14.2 | 16.2 | 21.3 | 26.9 | 29.8 | 32.2 | 34.0 | 35.5 | 36.9 | 39.0 | 39.1 | 38.3 | 37.5 |
| 90° | 9.9 | 11.3 | 12.7 | 14.4 | 16.4 | 21.5 | 27.7 | 31.5 | 33.5 | 35.1 | 36.3 | 37.5 | 39.6 | 39.8 | 39.1 | 38.7 |
| 95° | 9.9 | 11.3 | 12.8 | 14.4 | 16.5 | 21.0 | 28.7 | 31.7 | 33.9 | 35.5 | 36.8 | 37.9 | 40.0 | 40.3 | 39.8 | 39.5 |
| 100° | 9.9 | 11.3 | 12.7 | 14.2 | 16.3 | 22.3 | 28.8 | 31.7 | 34.2 | 35.8 | 37.0 | 38.1 | 40.3 | 40.6 | 40.3 | 40.0 |
| 105° | 9.8 | 11.1 | 12.5 | 14.0 | 15.7 | 21.0 | 28.3 | 31.4 | 34.0 | 35.8 | 37.1 | 38.2 | 40.3 | 40.7 | 40.5 | 40.3 |
| 110° | 9.7 | 10.9 | 12.2 | 13.6 | 15.1 | 17.7 | 26.8 | 31.0 | 33.3 | 35.5 | 37.0 | 38.2 | 40.2 | 40.7 | 40.6 | 40.4 |
| 115° | 9.5 | 10.6 | 11.8 | 13.1 | 14.5 | 16.5 | 19.9 | 30.0 | 32.6 | 34.8 | 36.6 | 37.9 | 40.0 | 40.3 | 40.4 | 40.1 |
| 120° | 9.2 | 10.3 | 11.4 | 12.5 | 13.7 | 14.9 | 17.4 | 25.8 | 31.8 | 34.0 | 35.6 | 37.4 | 39.6 | 40.0 | 40.0 | 39.6 |
| 125° | 8.9 | 9.9 | 10.8 | 11.6 | 12.4 | 13.5 | 14.7 | 16.3 | 29.7 | 32.9 | 34.9 | 36.4 | 39.0 | 39.6 | 39.6 | 39.1 |
| 130° | 8.5 | 9.4 | 10.0 | 10.8 | 11.9 | 13.1 | 14.3 | 15.5 | 17.1 | 18.0 | 33.4 | 35.4 | 38.1 | 38.9 | 39.1 | 38.6 |
| 135° | 8.2 | 8.7 | 9.5 | 10.5 | 11.5 | 12.6 | 13.7 | 14.8 | 16.2 | 17.3 | 18.4 | 20.0 | 37.0 | 38.0 | 38.2 | 37.7 |
| 140° | 7.6 | 8.2 | 9.1 | 9.9 | 10.9 | 11.9 | 12.9 | 14.0 | 15.2 | 16.4 | 17.7 | 19.1 | 22.1 | 35.4 | 30.7 | 35.0 |
Predicted speeds from the velocity prediction program. Sea-trial targets achieved with manual foil trim; the automatic flight-control system comes online after calibration.
- VPP targets calculated at
- 20,280 kg
- Design racing displacement
- Sea trials sailed at
- ≈ 21,500 kg
- As-built racing displacement
Every circled target was reached with the boat about 1.2 tonnes heavier than the weight the predictions assume.