Radial sawmilling makes sense however you slice it.
By Finn Seccombe
Australians have a peculiar knack for inventing. The polymer bank note, Wi-Fi, Vegemite, black box flight recorder, the bionic ear and the Hill’s Hoist to name a few. In Traralgon, Victoria, an inventor with a social conscience has come up with an idea that is changing the way we turn trees into timber. Andrew Knörr’s radial sawmill is possibly the first major innovation in milling technology since the industrial revolution. It slices up logs into long wedge-like segments, much like you would slice up a pie. This method has increased timber recovery radically and produces quarter- sawn and back-sawn boards with unrivalled stability and durability.
Andrew Knorr – the inventor.
The name Knörr has its origins in Viking culture. It was the name given to the robust Nordic sailing ships used for Atlantic voyages over a thousand years ago. It might seem like a bizarre coincidence, but these ships were constructed using planking from radially split logs. So durable were they, there are still intact remains of some of these original vessels. Coincidence or not, Andrew Knörr is busy applying the remarkable benefits of radial sawn timber to the complex needs of 21st century building and construction.
At heart, Knörr is a conservationist. The inspiration for his first sawmill invention, the “round pole milling machine”, was born out of a drive to make use of small plantation-grown hardwood. Substantial inefficiencies and waste in the native sawlog industry (particularly timber from old growth forests) spurred Knörr to devise a system to cope with cutting small diameter eucalypt. He adapted the round pole milling machine, which was specifically designed for pole frame construction, to be able to cut radial wedges for use as weatherboards and panelling.
In the early 1990s Knörr teamed up with highly-awarded Victorian architect Greg Burgess and was contracted to supply 40,000 linear metres of boards and panelling for the Eltham Library just outside of Melbourne. This required rebuilding the mill “on the run” and he scaled up the original prototype to cope with the size of the job. Burgess was very impressed with the quality and stability of the product and went on to specify radial timber for many projects, including the Uluru Kata-Tjuta National Park Cultural Centre and, more recently, his Mornington Peninsula “Stone House”.
Early on, there were many sceptics of this radical new approach to sawmilling. One old sawmiller said he would eat his hat if this crazy idea actually worked. (He was later reported to have a belly ache or some time…) After almost thirty years of operation, countless successful architectural projects and with the recent purchase and $6m upgrade of the original Yarram Mill, Knörr’s radial sawmill has certainly proved itself in the field.
Radial-sawn – what are the benefits?
Cutting boards out of a log with a conventional sawmill is much like trying to fit square pegs in a round hole. It doesn’t really fit; not without a whole lot of waste. The goal has always been to produce as much true quarter-sawn and back-sawn boards as possible.
Timber products with quarter-sawn and back-sawn grain alignments have the most desirable characteristics for industry – that is, stability, strength and durability. As the diameter of logs gets smaller, the recovery percentage of usable timber also shrinks. This means trees have to be of a significant age and girth (usually 50 years or more) before harvesting and sawing are viable.
Problems associated with cutting small diameter logs are further compounded by the phenomenon of “growth stress” – that is, the tendency for boards to bow or spring away from the heart of the tree as they’re cut. Apart from wasting large amounts of timber, this tendency also causes saw pinching and other related perils for the mill operator. Growth stress is especially prevalent in fast-grown eucalypt.
Knörr’s radial saw technology has been designed in a way that releases growth stresses evenly in each timber section. This means that stable boards can be cut from small diameter logs safely and efficiently. Waste is reduced dramatically and fewer logs are needed to produce a given amount of product. The radial mill at Yarram uses CNC (computer numerical control) for log alignment to make best possible use of any given log. Defects and asymmetry are taken into account, resulting in very little waste residue. Because the saw always cuts at right angles to the trees’ growth rings, every board is, in effect, quarter-sawn. These wedges can then be processed into boards which are perfectly back-sawn.
At this point you are probably asking: “But what about the sides or edges of the boards – won’t they be on an angle due to the radial saw pattern?” The answer is, of course, yes. Weatherboards were the first product to be sawn radially – an obvious choice as they are already made with tapered sides (this is so we don’t have to nail through the double thickness of a board when applying cladding). Architects have since used other products with tapered edges such as decking and vertical board cladding with great success. Most timber for building, however, requires that the boards, studs and beams have sides and edges at 90˚ to each other. If removal of the angled sides of the radial boards is required, it is achieved by re-sawing and machining using conventional milling processes. The percentage of timber wasted in this step is still significantly less than that which occurs in conventional sawmilling.
Radial-sawn and agro-forestry – how they fit together
Perhaps the most significant benefit of the radial sawmill is its ability to make high value product from fast-grown plantation timber. As access to old growth forest is becoming more restricted, less sustainable and increasingly unattractive to consumers, we are looking towards the plantation and agro-forestry sectors for answers. In the past it has not been viable to harvest hardwoods for high-quality timber younger than about 50 years. With this new technology, the turnaround can be 20 years or less. This opens up a unique opportunity for investors who were previously excluded from the industry due to the long wait on returns.
Chris McEvoy, former CSIRO wood scientist and owner of Radial Timber Australia Pty Ltd, has partnered with Heartwood Plantations and other industry bodies to launch an initiative called Touchwood. The Touchwood campaign aims to minimise the impact of the timber industry on the environment, while supplying Australians with beautiful, durable hardwood timbers. Together, Radial Timber Australia and Heartwood Plantations have planted over 2,000,000 trees in Gippsland Victoria, with the first plantations established in 2003. The species planted are indigenous to the Gippsland area: Yellow Stringy Bark, Southern Mahogany, Silvertop Ashand Spotted Gum – all known for their durability and fine aesthetic.
Heartwood confidently states: [with radial saw technology] “our hardwood plantations can be milled from 22 years and still yield the same as a 40+ year-old tree.”
Builders and architects: watch this space
Having worked as a shipwright and builder for many years, I am always dubious when I see an “innovative” new product on the market. The thought of receiving a call from an old client that says, “You’d better come and take a look at this – it’s not good” is enough to ruin anyone’s weekend. When I first heard about the radial sawmill more than 15 years ago I was intrigued, but not enough to draw me away from tried and tested methods. If it is going to fail in some unexpected way I would prefer it happened to an eager early adopter rather than me.
It has taken visionary architects like Greg Burgess, Simon Knott and Ric Zen to demonstrate to the industry that radially sawn timber is the way ahead. Their use of radial decking, cladding and structural timbers now goes back 20 years, and has shown that these products can stand the test of time in Australia’s harsh conditions. What’s more, builders and architects have applied their own ingenuity to come up with uses for radial timber (for example, pivoting louvres that control sun exposure), that the inventor and sawmiller hadn’t dreamed of.
Micro mills in the developing world
Developing countries such as Uganda and Kenya are currently investing large amounts of land and resources to plant eucalyptus species for building materials. Ideally, communities need fast access to cheap, durable timber. As the industry is quite new (and the trees relatively young), growers and sawmillers are faced with the challenge of meeting building demand with logs that are not suitable for conventional mills due to growth stresses and poor recovery rates.
Knörr believes that radial saw technology holds the answer. It can produce “off the saw” products that don’t need to be seasoned or machined. Boards are stable, strong and durable – even in Africa’s extreme climate. The technology is ideally suited to small diameter logs which can be utilised in as little as 15 years from planting in the hot tropics. It would not be unreasonable for a standing tree to be cut, milled and used on a building site within days. Radial saw technology would give farmers a much faster return on their investments, greater recovery from the trees they have grown, and at the same time reduce the impact of logging on dwindling native forests.
Changing consumer demand – who cares about sustainable timber?
All around us we are seeing consumers make demands on industry to supply cleaner and greener products for their bodies and homes, based on health concerns and environmental impact. Given the choice between buying a sustainably-sourced product and one that isn’t, many consumers will choose the former – provided it’s affordable and reliable. Likewise, as the X and Y generations take up leading roles in industry and small business, we are seeing a new code of ethics emerge that places high value on environmental sustainability. Forestry, sawmills and timber retailers are under increasing pressure to demonstrate an ethical chain of custody for timber products, and this movement will continue to grow.
Radial Timbers Australia and Heartwood Plantations have developed a partnership that is based on a vision for a sustainable future. They are busy buying up unused and degraded farmland to plant native hardwood species that will provide the sawmill with a sustainable livelihood into the future. Every step of the process has been carefully considered for both its impact on the environment and its ability to make a healthy profit. Technology that can turn plantation eucalypt into durable, high-quality building material is just what the industry needs to motivate a permanent shift away from logging native forests.
Architects like Ric Zen, Greg Burgess and Simon Knott are playing a vital role in championing radial timber. Their awe-inspiring projects demonstrate to clients and the public that “sustainable” can also be practical, aesthetically pleasing and affordable. Yes, you can have your cake and eat it too.
Australia’s timber deficit: keeping the buck here
Australia currently imports around $5.3 billion of timber and timber products per year, while our exports are $3.4 billion. That makes a $1.9 billion trade deficit. On the current trajectory of population increase, demand is only going to grow. Unfortunately, little investment has gone into long rotation hardwood plantations and the softwood industry has more or less flatlined. Foreign exporters take advantage of our strong currency, hurting local suppliers and forcing them to find efficiencies to stay in the game. It is clear that we need more plantation-grown trees and inventive ways of turning them into building materials and paper pulp with shorter turnaround times. There are many innovative processes such as rotary veneer and cross laminated timber (CLT) that are currently value-adding to what were previously considered low grade saw-logs.
Conventional sawmills have come a long way with automation and higher efficiencies but they are still restricted to saw logs that are half a century old. We simply don’t have enough logs of that age for a sustainable future. Andy Knörr’s radial mill may be just what the doctor ordered.
