Crafting a Life - Episode 14

Tuesday, April 12 2016

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Hello, and welcome to Crafting a Life.
I’m Evan Dunstone and this is the Dunstone Design podcast
Episode 14, “What do you do when it all goes terribly wrong?”

Craftsmanship is a relationship with materials. The really exciting craftsmen are those who take wood and, through a deep understanding of it, go to the edge. This is where new ideas, new forms and fresh approaches come from. This is also how national styles of furniture emerge.

Let’s look at the Windsor chair for a second. Traditionally, English Windsor chairs were made from ash and elm. The specific properties of both these timbers were understood and taken advantage of by traditional craftsmen. You used Elm for the seat and ash for the spindles. Elm is strong and relatively light, and, most importantly, it resists splitting when a round through wedged tenon is driven home. Ash steam bends well and turns well. If you split ash with a froe, you will find the right line in the grain and get sure, dependable stock to work with. A Windsor chair properly made with Ash and Elm is a perfect harmony of materials. They are like Ginger Rogers and Fed Astaire, strawberries and cream, Torville and Dean; the properties of one are enhanced by the properties of the other.

Only an idiot would try to make a Windsor chair out of a timber such as red gum. Almost every property and characteristic of red gum would fight the design logic of the Windsor chair. As it happens, the early settlers quickly discovered that very few Australian timbers had the properties required to make Windsor chairs, so designs like the Jimmy Possum chair, which responded to Australian timbers, emerged. Modern Australian chair makers should be trying to understand the properties of cranky timbers like red gum, and then designing a chair form that benefits from those properties, but I must say that such experiments come with a lot of risk.

We currently have a superb set of Australian designed and made chairs in our workshop undergoing repairs. They need repairs because the laminated sections of these chairs have failed rather catastrophically.

The designer/maker of these chairs is now retired from woodwork, but he was most active in the 1990’s and I really enjoyed his work. This guy, we’ll call him Darryl, was exploring some of the minor Australian species, and trying to push those timbers to their limits. In particular, he used a lot of Sydney blue gum and forest oak, a type of Casuarina. He experimented with a lot of curved laminations, because he thought that this was the best way to take advantage of the properties of his material.

The timbers he used are hard and full of resins. I suspect that Darryl read the same CSIRO article on gluing Australian hardwoods that I did back in the 1990’s and it recommended Urea formaldehyde. If I remember correctly, the tests were all based on the long grain gluing of uniform boards. Sometimes these sorts of test results can be misleading, because the results “in the field” can differ from the testing environment, with some pretty alarming results.

Let me tell you a little story. In my first year out in business, it so happened that I glued up a set of eight chair seats, but I ran out of urea formaldehyde after six seats. I was under time pressure to deliver the chairs, so I guiltily glued up the remaining two seats with a cross linking PVA. That was on a Friday. All weekend I worried about those two seats. I should have just ordered in some more urea formaldehyde and waited until it was delivered. Surely the clients would have understood?

On Monday I went back into the workshop, shaped and sanded the seats, and fitted them to the frames. All the seats had been carefully selected from the same tree, a particularly nicely figured red ironbark.

The next afternoon I was sitting in my office and the day had warmed up, with a storm brewing. Around 3pm I heard a loud bang. I walked into the workshop but I couldn’t find what was amiss.  A few minutes later, the same bang. This time I discovered that two of the 8 seats had popped along the glue lines. A third popped while I watched. I was devastated. Six of the eight seats failed. When I removed the seats, I found that they were all cupping in the same direction, due to the shaping I had done the day before. I had released the stress on one side of the seat without balancing it out on the other. All it needed was a change in the humidity and the temperature, and off they went.

But why had two not cracked? Sure they were badly cupped and thus unusable, but the glue lines had held. They were the two seats that I had glued with the cross linking PVA. I knew this, because I had marked them on the underneath, precisely because I was worried about them.

There were two lessons here; the urea formaldehyde had failed as soon as the conditions were no longer ideal, and you can’t just hog out a shape on one side of a piece of Australian hardwood without consequences. Incidentally, this technique would have been fine with a nice piece of quarter sawn black walnut. This was back in 1998. These days we take a hardwood board, resaw it on a special bandsaw, pre-shape it to remove the stress, re-flatten it on a special jig prior to assembly, spin out an interlocking edge profile and glue it up with a polyurethane glue. This is our famous wave seat.  We can make the wave out of any Australian hardwood, and any other timber for that matter, as long as the grain is sound. They are thin, light, comfortable and beautiful; most importantly, they respond to properties and eccentricities of Australian timbers.

So why had Darryl’s chairs failed? He was using twisted, tapered laminations. He was gluing up “off the saw” using the urea formaldehyde. I know this is getting a bit technical, but stick with me. A curved lamination is made from gluing several thin strips of wood around a curved jig. When the glue sets, the shape is now held. A twisted, tapered lamination is the same thing, however the jig has a twist as well as a curve, and the thin strips are thicker at one end than the other.  The glue lines are under a fair bit of strain, just like the glue lines on those cupped seats of mine. Urea formaldehyde sticks well, but it is brittle and it literally breaks under the right type of stress.

Then there is the way that Darryl used to cut his laminations. He glued them up straight off the table saw. In theory, this is good technique, because the saw blade leaves fine striations on the face of the timber, giving you a keyed surface to glue to. This technique crops up from time to time in various articles and books, but they are almost invariably talking about northern hemisphere timbers. Unfortunately, I don’t think that this technique is ideal for the Australian timbers that Darryl was using, because they are so hard that when clamped up, those striations don’t compress the way American walnut, for example, might. Our face to face laminations here at Dunstone Design are done out of a wide belt sander, and we have never suffered a delamination. It has been my experience that Australian timbers are better abraded than cut when preparing them for lamination.

As I already mentioned, Darryl’s chairs were beautifully engineered, and all the non-lamination joints are as sound as a bell on these 20 year old chairs. And even though the back legs, the crest rails and the curved back slats have literally fallen apart because the failing laminations, the rest of the chair is in excellent shape. Why do I care? Well, the frame is incredibly light and flexible. The chair is wonderfully supple and alive. This was only possible because of the nature of the timber used and the way Darryl had designed in the flex, taking advantage of the strength and resilience of our timbers.

Darryl had come within a cigarette paper of developing a superb chair that responded to the very nature of our timbers. I suppose he looks back on this episode with some bitterness, because a whole body of his work has suffered this delamination problem, but I think cutting the laminations straight off the saw, in conjunction with a glue (urea formaldehyde) that had both been developed for the properties of typical northern hemisphere timbers were Darryl’s undoing.

Looking at the technical successes of the design, I note that it features an outrigger leg with a single vertical tenon. I would have bet a case of good beer that those front legs would have failed by now. Years ago, I used basically the same joint on one of my chair designs, but we suddenly started getting a few back with broken tenons. The first couple of times we blamed the different clients for being too rough on their chairs. The third time we got a chair back with exactly the same break point, we knew that we had a design flaw. This led to our developing the twin tenon joinery you will now find on all our chairs that feature outrigger legs. Australian timbers are hard and strong, but they can also be quite brittle. If you make a rigid chair frame and then put an outrigger leg on it with a single tenon, the energy from any sudden jarring received by the front leg is transferred directly up to that single tenon. Snap. I have repaired this fault on my own chairs, as well as two different designs made by two of the most respected makers in Australia. It is a common mistake.

Darryl’s front leg joinery had survived, and I am confident that this is largely because his chair frame was so elastic. I think the shock was able to transfer through the whole frame of Darryl’s chair, just like a good sword flexes under shock, rather than snapping. I hasten to say that I still think that a twin tenon is prudent, but Darryl’s flexible frame worked.

Darryl was doing what a craftsman should do; addressing the nature of local materials. If he had been working with northern hemisphere timbers, he probably could have followed northern hemisphere rules without much danger. Yes, it went horribly wrong for him in some ways, but he got a lot more correct than I think he realises. I have learned a lot from his failures, and I would like to think that, in some ways, I kept going where he left off.

I should close by pointing out that I am not repairing these chairs of Darryl’s just because I’m a big hearted bloke. No, the original client has approached me to reverse engineer these chairs and re-build them because she loves them so much. She has approached Darryl to do this work, but he is long out of the game and is not in a position to do the work. All his jigs, templates and equipment are gone.

I am delighted that the client has such an attachment to the design, and I hope that Darryl takes heart from these level of appreciation.  As you can imagine, the reverse engineering of a chair like this takes time and the repairs will cost at least as much as she paid for them originally, but she can see beyond the technical shortcomings of the laminations and appreciate the design for what it is; an excellent attempt at the perfect Australian chair.

You have been listening to Crafting a Life, the Dunstone Design podcast on all things furniture and woodwork. I’m Evan Dunstone, and I look forward to your company next time.



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