High-tech tool puts timber to test

By SIMON COLLINS, science reporter

A forestry business has developed a computerised tool to test the strength of timber in the field - but wood that fails the test will still be used to build local houses.

Carter Holt Harvey has developed the tool, called "Hitman", because it needs Machine-stress-graded timber for its new, $130 million laminated veneer lumber (LVL) mill at Marsden Pt.

It sees a multimillion-dollar worldwide market for the Hitman, especially in countries such as Australia which require machine-stress-grading for almost 100 per cent of home building.

But most home builders in New Zealand still choose timber simply by looking at it.

"We do use machine-stress-graded lumber in certain applications, but not usually in buildings," said Peter Carter, resource technology and commercialisation manager of Carter Holt's technology subsidiary, Fibre-gen.

machine-stress-graded timber is used for 40 to 50 per cent of new houses.

"Roof trusses have stress-graded lumber, but regular studs don't, and there is no regulation that says you have to use it. In Australia they have that requirement, and have had for some years."

As its name suggests, the Hitman works simply by being placed next to a log which is hit sharply with a hammer. The device gauges the log's stiffness by measuring the speed of the sound wave the hammer produces.

The Hitman's built-in computer records every result, which can be emailed back to head office to give the forestry company a real-time measure of its wood resources.

Scientists at Industrial Research designed the sturdy device to survive forestry's tough conditions.

An initial production run of 100 will sell at $10,000 apiece.

Mr Carter said that almost any trees left to grow for at least 30 years would be stiff enough to pass the Hitman test, making them suitable for scaffolding and other specialist building applications that use LVL.

But most trees were now felled after only 24 to 27 years, when only 40 to 50 per cent of the timber reached the Hitman standard.

"The wood that is not strong enough for those purposes is still fine for studs and for appearance as long as the sap stain doesn't get it, and for furniture and industrial uses."