The incredible hull

By ROBIN BAILEY

A tiny, 4.6m jetboat is taking the New Zealand marine industry on an important first step into the future of building composite boats. It is lighter and tougher than the aluminium and GRP boats of the past. It also means a less hazardous work environment for the people building the boats.

Northland Contract Boatbuilders in Whangarei has just completed the hull of the first resin-infused boat to be built in New Zealand.

The finished product is the result of a long and expensive collaboration between the Whangarei builder and the Auckland leaders in composite construction, High Modulus and Adhesive Technologies.

NCBB principal Fraser Foote, a keen jetboater, says it is appropriate, given the history of river boating in New Zealand, that the first craft built by resin infusion is a jetboat. His recreational activities include adventure and whitewater jetboating action on the Wanganui, Motu and Waioeka rivers, among others.

"I had some success with a foam/Kevlar boat that convinced me to take a step further when I decided to build a new one," he says. "The boat wasn't an ideal whitewater performer, so after trying a Rapid Runner jetboat in the South Island I decided that was the way to go.

"I took a mould off the Rapid Runner and decided that if we could reduce the weight we would have a boat that performs better, bounces over rocks better and uses less fuel. An alloy jetboat weighs 850kg to 950kg complete, and we can get that down to 600kg complete using composites. Using resin infusion and a Kevlar/Herex foam sandwich, the hull weight drops from 250kg to 150kg."

Foote says the first hull weighs just 95kg. By the time the deck, floors, structure and screen are added the total will be 150kg. To achieve this result he sent NCBB production manager Jason Farr to study resin infusion at the University of Plymouth in Britain at a cost of $10,000.

"The resin-infusion technique is not simple," Foote says. "It takes technology, time and experience and we have put a lot of investment into getting it right. To be almost spot-on with our first boat is a real achievement."

High Modulus and Adhesive Technologies have also made a huge investment in understanding and developing the resin-infusion technology and are now geared to assist boatbuilders, as they have with NCBB, to take advantage of the technique.

Resin infusion was developed in the United States to help to meet stringent styrene emission and workplace health regulations, the sort of strictures that are now being introduced in this country.

High Modulus managing director Richard Downs Honey says the technique has an important role to play in the future of composite boatbuilding.

The benefits include excellent quality, better resin reinforcement ratios and fewer air voids, he says.

It also prevents volatile organic compounds from entering the air.

His company brought Mark Hildesley from the US to work on the new technique. Hildesley has extensive experience with infusion boatbuilding at two of the major American firms, North End Composites and the Hinckley Company.

High Modulus also sponsored a presentation to this year's NZ Boating Industries' Association conference in Auckland by Dr Tim Searle from the Advanced Composites manufacturing centre in Plymouth.

Infusion of resin

Resin infusion is a development of the proven vacuum-bagging technique. Special vacuum-bagging materials, and in some cases layers of laminate, assist the transfer of resin through the reinforcements.

The reinforcements are placed dry in the mould and covered with resin transfer materials and a vacuum bag. The vacuum pulls the wet resin into the spaces around the fibres and core materials to form the final laminate.


Infusion processes can utilise most reinforcements, although some styles of fabric are particularly suitable.

Also, there are certain characteristics in the resin system which can be varied to ensure optimum performance.

In effect, the boat is formed in a bag and the builders are not exposed to emissions that can cause health problems in traditional GRP boat- building.