I spent four years slamming yacht hulls in a tank

11 August 2026

Faculty of Engineering and Design, Science and technology, Doctoral

Brainwaves is a new weekly Post and Sunday Star-Times feature showcasing the best, brightest and most innovative minds in New Zealand through their masters or doctoral research. Each week, there are four first-hand accounts of research from the country's universities. These are republished on the University website two weeks later.

Have you ever driven fast over an undulating gravel road? It's a pretty rough experience. Teeth shaking. Car rattling. You're just waiting for something to break. Well, imagine that those bumps in the road are several metres high, and you're doing it without any suspension…now you have some idea about the conditions an ocean-racing yacht might experience.

Sailing at full speed in some of the worst conditions on the planet, these boats are constantly slamming into waves, which is one of the main causes for any structural damage they might experience. During racing in the 2021 Prada Cup, American Magic AC75 rose out of the water and slammed down causing serious damage and a major rescue operation off Auckland's East Coast Bays. This is exactly the sort of problem I was looking into - how to test hull strength under such scenarios.

Modelling the complex impact of a wave hitting the hull is too difficult and time-consuming to do in normal design.

Dr Connor Pearson, Faculty of Engineering and Design Waipapa Taumata Rau, University of Auckland

The problem is that 'slamming' is very hard to predict and design for.

Loads can depend on the boat's orientation, the shape of the hull, its speed and the sea state. This means that every time a boat slams, it's inherently a random event, and difficult to analyse. Modelling the complex impact of a wave hitting the hull is too difficult and time-consuming to do in normal design. Instead, traditional methods treat it as a single, evenly distributed pressure with the same total load. These methods don't account for the highly dynamic nature of a water impact, and so may not be appropriate for today's high-speed foiling yachts and power boats.

What the boats are now designed for is often not what they actually experience in the ocean. What looks good based on the engineer's calculations may inadvertently make the boat more susceptible to damage and failure. This is where my thesis research came in.

With advice from local and international industry partners, I set out to design and construct sections of racing yachts, then got to smash them into water using the unique testing facilities available in the Faculty of Engineering and Design at the University of Auckland.

It never gets old watching a one-metre-wide, 30kg section made of high-performance carbon fibre smash into the water at more than 30kph. On impact, 20 tonnes of load goes through the section in less than one hundredth of a second. It's an incredibly violent test. In fact, it is quite scary to be standing right next to the big tank when this happens … the whole building shakes, tonnes of water is blasted upwards, and you feel a wave of pressure pass over your skin.

These sections were covered in sensors, so I could measure exactly how a hull behaves during a slam. Undertaking some complex simulations, which combined the fluid and structural responses, I examined every detail. This included looking at how the water ran along the outside of the hull, how the section was twisted and deformed by the impact, and understanding exactly how and why the sections broke.

By comparing the results of these tests with those of the design engineers, I determined just how different a real-world slam is from the simplified models used by industry, and the answer is - a lot.

I found that the simplified method of strength testing and analysis for boat design cannot reliably predict the forces of a wave impact. This inaccuracy can result in a hull that is either too weak to survive an ocean race or so heavily built that it is no longer competitive. In the pursuit of speed and victory, neither of these is ideal.

I was able to then suggest some modifications to the simplified model to improve its accuracy. Some of these points are currently being considered by the International Standards Organisation for use on small high-speed watercraft worldwide.

In the future, if you're riding in a jetboat or sailing on a choppy day, the safety and resilience of your boat may well be down to the results from my experiments.

Associate Professor Tom Allen and Professor Mark Battley (both University of Auckland) supervised Connor Pearson's research.

Originally published on 26 July as part of the Sunday-Star Times Brainwaves feature. Read the original on The Post.

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