Please select your home edition
Edition
C-Tech 2020 Battens 2 728x90 TOP

America's Cup: The importance of choosing the right materials and process - prepreg or infusion?

by Emirates Team NZ Media 19 Mar 03:05 PDT 19 March 2022
Emirates Team New Zealand Wind Powered Land Speed project - March 2022 © Emirates Team New Zealand

Like building anything, a house, a fence, a car or a boat, considerable thought is given to the materials used for the purpose of the build. It is one of the first considerations when matching objectives with budgets and time.

The Emirates Team New Zealand Wind Powered Land Speed project is exactly the same, as Mechanical engineer Tim Meldrum explains, "In the design process when we're trying to determine just how we're going to build all of these parts, the build team plays a major role, sitting around a table, thrashing out just what the process will be."

The build team are the Emirates Team New Zealand boat building team based in the ETNZ production facility on Auckland North Shore, a mix of young apprentices through to some of the most experienced boat builders in the New Zealand marine industry.

They know all there is to know about the materials used in their trade, and when it comes to composites, the main two options of construction are a pre-impregnated carbon fibre and dry fibre with a wet laminate.

"As the name suggests pre-preg is carbon fibre pre-impregnated with resin," explained boat builder Kurt Riechelmann. "We would usually use pre-preg because you get perfect resin ratios out of it and it is not until it gets hot that the resin will flow and it's almost like laying down dura-seal, or something like that."

However 'pre-preg' does not come cheap so you need to consider the costs and weight ramifications- like when weight savings are imperative in a foiling AC75 that needs to be as light as possible to take flight.

Emirates Team New Zealand build their AC75 hulls from pre-preg since a small saving over a larger area like a boat hull can add up a lot of weight. Also it allows the team to hit strict weight limits in the AC75 class rule, a lighter hull structure gives you more freedom to develop systems within the hull weight limit.

In the case of the land speed yacht, the pre-preg composites are reserved exclusively for what's in the air above the craft- but why? "We can be a bit more focused where we push the tech, so the mast, the wing, the spar, if we make that heavy it steals the righting moment and the stability that you need to generate power. So we are more weight conscious." explained Meldrum

But in the case of the mainfuselage body? "We will adding some ballast for downforce grip in the main body so it is much less sensitive to weight than the wing. Therefore with the land speed record craft the body is less mass critical, the weight is down low and does not affect righting moment too much. So pre-preg does not justify itself in this case so the smarter move is to save the time and money so we use dry fibre infusion and wet laminate."

Some of the main body elements lend themselves nicely to the infusion process where multiple layers of carbon are placed carefully in a mould dry, then a vacuum created within a bag and resin is released to flow into the carbon and cure as a rigid part. This process is great for thicker laminates without core and because the laminating process is done dry, it is not time pressured with resin curing.

Dry carbon fibre infusion is still a high tech material and process if you compare to the likes of a production trailer boat.

For the production team it is a more user friendly and speedier option than pre-preg in the construction. Estimates being that it would take a quarter of the time to lay up the body of the land speed craft as it would with pre-preg. But because it is slightly heavier way of laminating carbon, it is much harder to achieve the optimum resin to fibre ratio, so you end up carrying a little extra resin that you don't need in theory.

So the devil is in the detail and there are margins for error, but having the experience and knowledge of how to carefully set up the infusion process can be the difference between success or disaster in the production.

"It's a bit of a dark art, infusion." said veteran ETNZ boat builder Peter 'Pee Wee' Ockleston.

"It can go wrong and it can seriously go wrong, but the processes that we've been working on over the last 15 years or so, we've got it pretty close to getting right every time."

It is this talent and knowledge that the whole team relies on in the ETNZ production facility that is a hidden secret to success for many Emirates Team New Zealand production projects. "It's nice to have a real depth of experience within our build team so we can draw upon all forms of manufacture. We really can pick the process that best suits the part no matter what it is." concluded Tim Meldrum.

Related Articles

Project Land Speed: Horonuku arrives in Australia
Horonuku has arrived safely in Australia, clearing customs this week in Adelaide Horonuku has arrived safely in Australia, clearing customs this week in Adelaide after its journey via sea from Auckland over the past month or so. Posted on 5 Aug
Project Land Speed: Pod power explained
ETNZ's Tim Meldrum explains how the pod is used on Horonuku to optimise righting moment Emirates Team New Zealand's Tim Meldrum explains how the pod is used on Horonuku to optimise weight carried depending on the windspeed. Posted on 30 Jul
Emirates Team NZ designer wins Women's WASZPs
Elise Beavis was crowned Women's WASZP World Champion at the WASZP International Games in Lake Garda Emirates Team New Zealand designer Elise Beavis was crowned Women's WASZP World Champion at the Waszp International Games in Lake Garda, Italy. Posted on 18 Jul
Project Speed: Waiting is best, patience is a must
Constant evaluation and adjustments of plans are essential to the success of the overall objective With a project as highly contingent on weather and conditions as the Emirates Team New Zealand wind powered Land Speed World Record attempt, constant evaluation and adjustments of plans are essential to the success of the overall objective. Posted on 15 Jul
Project Speed: Waiting for the lake to dry
Venue for wind powered land speed record attempt still underwater - dates pushed back It would come as no surprise that a lake would normally have water in it. But what is surprising is that Lake Gairdner, the usually bone dry salt lake in South Australia, currently has a somewhat inconvenient amount of water in it. Posted on 10 Jul
America's Cup: Emirates Team NZ on the move
America's Cup champions to shift to new base in September on extended lease Emirates Team New Zealand confirmed today that the team has signed a lease of the former INEOS Britannia team base on Wynyard Point from Auckland Council and intends to have moved in by the end of September this year. Posted on 6 Jul
Project Speed: Certifying the record checklist
World records are not broken every day, nor are they ever easy to achieve, but they must be For Ashby, as the pilot at record breaking speeds that will need to exceed 202.9km/h, his control is not much more than a two finger operation on a lever, some foot pedal pumps and some small steering adjustments.. Posted on 2 Jul
ETNZ Project Speed: Ashby's Update -Testing ends
New Zealand-based testing program of Horonuku at Whenuapai Air Base - Phase 2 is complete! New Zealand-based testing program of Horonuku at Whenuapai Air Base - Phase 2 is complete! With the wonderful assistance of the RNZAF we have been able to sign off on the many pre-designed configurations and tuning of the main components of the yacht. Posted on 31 May
ETNZ Project Speed: Glenn's Diary Week 2 - Cut!
We are going to shorten the craft up and change the distance between the rear wheels and the centre Emirates Team NZ and the Project Speed team have been making the most of their testing at the Whenuapai base this past week in a range of weather which Glenn Ashby and the team have utilised to continue their sharp learning curve on ‘Horonuku' Posted on 27 May
Emirates Team New Zealand set to sail in Australia
Emirates Team NZ's next challenge will be to break one of the most difficult records in sailing After dominating on the water For the past 35 years, Emirates Team NZ's next challenge will be ashore, conducted in Australia, and aimed at breaking one of the hardest records in sailing. Posted on 25 May
Vaikobi 2021 Boots - FOOTERDoyle Sails 2020 - Redefining Boundaries 728x90 BOTTOMMarine Resources 2022 Salary Survey FOOTER