Hi. I’m Keith Decent and this is From the Ground Up. A podcast about how we make what we make, the materials, the tools, and the stories behind the things we build.
You may have heard stories recently, or come across an article in your feed; mysterious groups of scientists doing new things with wood, vaguely written or told like stories of a secret government organization trying to create superhumans in an underground lab somewhere. Invisibility, check. Fire resistance, check. Enhanced strength and durability, check.
Whatever the motives for these new formulations of one of mankind’s greatest constructive resources, it seems we’ve really been pushing the concept of “engineered wood,” to the logical limits these days.
And why not? We’ve already given it the power of flight.
November 2, 1947. Long Beach Harbor, California. Howard Hughes, no stranger to controversy, has taxi’d his most contentious project yet, the H-4 Hercules, around for its third and final test run across the surface of the water. Of the 7 reporters on board, among 29 other guests and crew, 4 had already left for the day. The three that remained would bear witness to the fruits of a 23 million dollar price tag (almost 270 million in today’s dollars) and 5 years worth of development.
As always, Hughes was piloting his own test flights. He brings the gigantic flying boat around, pointing the massive wooden body down the channel facing Cabrillo Beach. The wings, longer than a football field, align with the test path and the engines roar.
Back in 42, the military had a huge issue. They needed to resupply the troops fighting the Axis powers in Europe, but there were sharks in the water. Invisible sharks. Invisible sharks with guns. German U-Boat submarines were decimating US convoys out on the open seas. They needed a solution, they needed a flying ship.
The job eventually fell to Hughes. To him, what he had designed, what he was building, was one of the greatest engineering feats of all time. To much of the press it was a joke. To his enemies in Washington D.C., it was a sham.
“The Spruce Goose,” they called it. The nickname seemed to really get under Hughes’ skin. Perhaps that’s why it had stuck, despite the plane being made almost entirely using Birch.
Not just birch, though. They had used a new process, called “Duramold” to form the body of the plane. It needed to be lightweight, but still strong and Duramold was as light and strong as aluminum, the preferred material for the aviation industry made scarce by the war effort.
As an explanation of the Duramold process, let me read a 1945 advertisement for Fairchild Engine and Airplane Corporation in Aviation Magazine:
“THIS IS NO ALCHEMISTS DREAM.
Alchemists of old, in long, labored attempts, tried vainly to change common ores into precious metals.
While Duramold hasn’t changed lead to gold, in essence, Duramold’s engineers have achieved the alchemists goal. They impart new character to common materials.
In light, pliant materials - cloth, paper, glass fiber, wood veneers, cellular rubber, and many others - the Duramold process creates a backbone of strength. Laminations of these materials are bonded with thermosetting resins under heat and pressure, frequently using synthetic, lightweight core materials between laminations.
Duramolding gives them new qualities. Their pliancy is gone. They assume rigid strength, molded to precise specifications in intricate and complexly curved patterns.
Here, then, in an industry now devoted entirely to production for the Air Forces, lies the promise - and the reality - of new materials for builders of peacetime products. Here, as in all Fairchild research and engineering, lies “the touch of tomorrow.”
The ad not only explains the Duramold process, but speaks to the methodology and mission behind all engineered wood products. We take what we have, and through modification, transform it into what we need. We experiment, design, and innovate to further our current goals and to provide for the challenges that lie ahead.
Back in the harbor, the Hercules, the great floating beast, was picking up speed. It’s 8 engines roaring loudly as it skipped and shook across the choppy surface. The guests and reporters began to shift uncomfortably in their seats. This wasn’t like the other two runs. Either something was going wrong, or Hughes was up to something, or both. His plane had been at the forefront of a series of hearings held by congress. They called it a waste of time and money, they called Hughes a war profiteer, an accusation he believed to be a cover for their true motives, trying to put him out of business by request of his competitors.
It must have occurred to more than a few of the guests that Hughes was just the sort to push a test beyond its parameters in order to prove a point.
Suddenly the shaking had stopped. The engines still screamed their gruff tune, and, for 26 seconds, Hughes had shown his detractors exactly what to make of the so-called “Spruce Goose.” It flew. At a height of 70 feet above the surface of the harbor for one mile, the largest airplane ever built flew. A new kind of ship, made from a new kind of wood.
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Wood and Earth. That’s the way we used to build things. We carved stone from the ground, and we felled and harvested the trees. As we grew to understand these materials more, and where they came from, we learned to tell what kinds of earth can be made into brick, and eventually cement, and what types can be melted into glass. We learned what types of stone can be smelted into metals and what type of metals can be combined into alloys. We perfected our glass and our steel and our concrete and we used them to build fantastic monuments to the modern age. We used them to build skyscrapers. One of them, even half a mile high. Grand palaces among the clouds.
In our lofty aspirations, we had nearly forgotten about wood. It didn’t seem, in our beautiful visions of the future, that the humble trees could offer us much beyond a modest home, a few stories above the ground.
Some, like Howard Hughes, have described a vision of the future, the near future, in which the trees can lift us up into the safety and sanctuary of the sky. We’ve talked extensively on this show about plywood, but we haven’t given much time to its cousins, and while MDF, OSB, LVL, glulam, rimboard and other engineered products have been around for quite some time, they have been relegated mostly to small scale construction, like stick-built and prefab houses.
In Germany and Austria, in the 1990s, a new form of engineered wood product was being designed. Called “CLT” or Cross Laminated Timber, each section consists of layers of kiln-dried boards, stacked in alternating directions, just like plywood. However instead of using veneers, CLT uses entire boards. The result is a rigid, lightweight panel with good insulating properties that can be cut to nearly any dimension of thickness. The panels can even be prefabricated before they reach a build site, making construction less costly, less messy, quicker and quieter.
The panels are strong enough to be used as flooring, walls, or roof material within a structure, and in the 2000s, after being thoroughly researched and tested, it began to spring up in the European markets as an alternative to traditional building materials.
The new material has lit up the sustainable architecture world, it seems. If you google “world’s tallest wooden building” right now, you’ll find a number of articles from 2016 until present that seem to name a new bearer of this title every year, and several more that warn of upcoming challengers.
As of this episode, the tallest is a mixed use building is in Norway containing shopping, apartments, office space, a pool, a restaurant, and the aptly named, Wood Hotel. I am not even going to attempt to pronounce the name of this building. One I can pronounce was the former tallest wooden building in the world, the Commons Tallwood House in Vancouver, though it is made with concrete as well. Treet, another Norwegian project, it means “Tree” in english, was the tallest all wood, residential building until this year, standing at 49 meters, or 160 feet. This new one is nearly double that, at 85.4 meters, or 280 feet.
And if that isn’t crazy enough, the list of proposed wooden “plyscrapers,” as they’ve become known, is intense. London has plans to build the 1000 foot tall, Oakwood Tower which would become the second tallest building in the city. In Tokyo, plans are underway for a 1200 foot tall timber tower, named the W350, to be completed by 2041.
They are part of what’s called the “Mass Timber” movement. Why move away from concrete and steel? Well, right now it’s more expensive to build plyscrapers instead of doing things the old fashioned way. However those costs are expected to drop rapidly if the market grows and the processes are streamlined. The wood is also lighter to transport, carry, and build with than concrete or steel. Less heavy machinery and fewer giant trucks not only save money in the long run, but it also makes for a quieter, less polluted construction site. The possibility of prefabricating the timber panels also makes construction much quicker.
The burning question that gets asked the most when talking about timber construction is fire safety. And the answer lies in the material. Small wooden objects, like you’d find in a traditionally stick-built house, burn much faster and act like kindling for a fire. The thick, laminated panels of CLT and other engineered woods are much harder to burn due to their mass and composition. They might even outperform many traditional concrete and steel structures. The rest is taken care of by modern technology. Better, redundant alarm and suppression systems, for example.
One of the largest upsides is that instead of expelling tons of carbon into the atmosphere, as the processes for creating steel and concrete famously do, the timber actually sequesters carbon. The trees themselves gather and store carbon dioxide for their entire lives, and when harvested, that carbon is locked away in the material for as long as it lasts.
The tower in Vancouver, for example, saved 2,432 tons of carbon dioxide compared to other construction materials. That’s like taking 500 cars off the road for a year.
Wood, in its natural state is composed of 3 main compounds. There’s cellulose, the fibrous cell-wall material that gives the wood it’s hardness, and there’s lignin, the complex organic polymer that binds it all together. The third element is Hemicellulose, which interacts with both to lend even more strength to the wood.
Industries have long been using chemical baths to dissolve the lignin out of wood and use the remaining cellulose to make paper. Much more recently, however, the process had been used to alter the physical properties of the wood. Scientists have been able to create superwoods without needing to use old school lamination techniques.
A team from the University of Maryland, led by Lianbing Hu, have managed to create a wood product that is stronger than many titanium alloys. They say it’s about 12 times stronger than the wood alone, and about 10 times tougher. They’ve even managed to get it to stop a bullet in ballistics tests.
The bulletproof wood is created by removing the lignin and hemicellulose in a boiling bath of sodium hydroxide and sodium sulfite. Afterwards, the remaining cellulose is mechanically pressed at 212 degrees Fahrenheit (100 degrees celsius). This squashes it down to 20% of its original thickness, but now the cellulose is compressed into a thin, highly dense arrangement, held together by strong hydrogen bonds. This new material is stronger than steel and a fraction of the weight.
But why be bulletproof when you can just be invisible? The U of Maryland team has also managed to produce a transparent material using delignified wood. The first part of the process is the same, but instead of compressing the cellulose, they replace the removed natural polymers with an epoxy. The process takes about an hour, and produces a transparent, yet still a bit hazy, chunk of what looks like clear plastic. The cellulose infrastructure, however also makes it incredibly strong. Like the bulletproof version, they claim it is as strong as steel.
Both of these new superwoods possess very good insulative properties compared to metal and glass, and could be used as a much more thermally efficient building material than each, while retaining the desired structural properties.
From our humble beginnings, gathering sticks and arranging them make shelter, to our current phase of engineering marvels, wood has always been an incredible resource for humanity. Through the evolution of our understanding, we have rediscovered, time and again, how we can further manipulate this natural, renewable material in order to suit our needs. The needs of an ever changing society, the needs of a growing population, and the needs of our home, the planet. The earth gave us the material, we studied it and used it to get smarter, and now we use that knowledge to help ourselves, and the world in which we, and the trees, live.
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Thank you all, and I’m looking forward to another great year!
Until next time, this is Keith Decent saying, later makers.