Space-age materials for SkyPath

SkyPath would be slung under the city-bound clip-on and feature observation decks. Photo / Copeland Association Architects

Space-age composite materials evolved from New Zealand's boat-building and film-making industries are proposed for a cycling and walking path across Auckland Harbour Bridge.

A trust seeking Auckland Council underwriting support for a $31 million tolled "SkyPath" structure beneath the bridge's city-bound clip-on lanes is working with the Warkworth company that built most of the catamaran used by Oracle to win the America's Cup.

The firm, Core Builders Composites, hopes to share the proposed fabrication of 14m sections for the pathway among other industry players, potentially including the builders of Team NZ's catamaran.

Pathway trust project director Bevan Woodward said yesterday that his organisation favoured composite fibre and resin material over steel and aluminium, to produce a lighter and stronger structure for a similar price.

"It doesn't fatigue or degrade, will be easier to implement and will have much lower maintenance costs with a service life of well over 50 years."

He sees that as a strong selling point when the new council considers in December whether to support the project, as the trust intends gifting the pathway to the Super City within 20 years, once capital offered by a fund associated with the NZ Super Fund is repaid from tolls.

Those are expected to be set at $2 for each direct crossing, or $3.50 for access to two observation decks and exhibits beneath the pathway.

Mr Woodward said 63 modules, each weighing only about two tonnes, would be pre-cast and installed over fewer than 30 nights to minimise any disruption to bridge traffic.

The trust was also considering using ultra-light architectural mesh - developed as a spin-off from armoured costumes produced for the Lord of the Rings film trilogy - to wrap around the pathway, to shield cyclists and pedestrians from the elements.

Kaynemaile chief executive Kayne Horsham came up with the concept while working as artistic director for Weta Workshops, basing it on medieval chain-mail armour but now using advanced injection-moulding technology to produce mesh for buildings around the world, including a new block at Auckland University.

Mr Horsham said the structural integrity of the material was many times greater than that of other methods of assembly.

Core Builders co-construction manager Tim Smyth said his company has the capability to produce a master set of tooling, to farm out production of the pathway's structural modules to other boat-building firms while ensuring uniformity.

He said that even in the heat of the America's Cup campaign, the firm knew it needed to explore other opportunities, and put considerable work into developing "a composite solution" for the SkyPath project.

"This is not some temporary phenomenon - you will see a lot more bridges and structures built out of composites in the future."

Marine Industry Association executive director Peter Busfield hopes the SkyPath will become "an exciting showcase" for this country's technical expertise.