Carbon fibre steering wheel for the high-end marine market

The main challenge with this project was ensuring the steering wheel would meet certification standards. Carbon fibre marine steering wheels were rare at the time, and few had passed certification processes. The standards we had to adhere to were developed for stainless steel and were not particularly applicable to carbon fibre.

The most difficult requirement to meet was the impact test, which simulates a torso striking the wheel. An 80 kg weight swings into the weakest part of the wheel twice: one strike delivering around 160 joules, the second around 270 joules. To pass, the wheel can bend but not shatter; it must stay anchored to the helm shaft, and it has to remain usable as a steering wheel afterwards.

A significant technical contribution I made to the project was CAD modelling the tooling needed to manufacture the wheel’s carbon fibre knob and nut. I designed small trapped rubber tools to make carbon skins that would be bonded to stainless steel parts carrying the threads and mounting hardware. A challenge with the tooling design was being able to repeatedly produce the components. The tool had to produce the skin, release the silicone, then reload the cured skin with an alignment jig holding the steel part centred for bonding. Repeatability was particularly difficult to achieve for the knob tool as the knob spins on a bearing, and any offset shows up the moment it turns. To achieve consistent repeatability of the parts, I designed a cavity on either side of the tool, and a bar that the steel part bolted onto that would hold the part centred inside the skin.

The certification test was a stressful part of the project. We knew traditional carbon fibre construction would likely not pass, and we didn't want to manufacture parts and send them off to be tested by the certifying facility for time and money reasons, so we decided to replicate the test in-house. The client supplied a video of the official rig, and I got the job of building ours.

The first problem was how to safely swing the mass. Suspending 80 kg from the workshop ceiling and swinging it around didn't seem safe to me, so I reconsidered what we were actually trying to achieve. Less weight and more height would achieve a similar striking energy. We had silicon carbide sand available in the workshop, and after some calculations (E = mgh), I worked out I needed 20 kg of sand to achieve the required energy with a safe swing height. To get the amount of energy required, we had to raise the bag about 800 mm above the impact point for 160 joules, and 1400 mm for 270 joules. We bolted the wheel, just off the floor, to a steel shelving unit anchored to the floor, and swung away. It worked a treat.

As we ran through the testing using the sand bag rig I developed, it became clear why it was crucial for product certification. An early-generation wheel, made with carbon prepreg over Expancel core, was an outstanding product that delivered on the functional and aesthetic aspects of the scope. It was an amazing first part with an incredible finish straight from the tool, weighed next to nothing, and when my boss and a colleague dared me to stand on it, it didn't even flex. The sand bag test rig, however, absolutely obliterated it.

The wheel that did eventually pass was a different construction. The final product comprised two skin profiles made simultaneously in an aluminium tool with rubber trapped between. Once formed, the rubber was removed and the cavity packed with high-impact epoxy and unidirectional glass fibre. The weight difference between the Expancel wheel and this one was very noticeable, but it was not a concern to the client.

This project was a real starting point in my career. I learned the process of developing a product to scale, I designed my first production composite tooling, and built my first test rig.