Lost Art Press

Category: The Stick Chair Book

Add Strength Without Bulk

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This week I am building a Hobbit-y chair for a customer in black cherry instead of white oak. Is cherry strong enough for a stick chair such as this? Of course. How do I know? I added 1/8” in diameter and thickness to some key components. So now I can sleep without worry.

If the above paragraph makes little sense, then you haven’t read my chapter on wood in “The Stick Chair Book.” No, this isn’t an advertisement to twist your arm into buying the book. Instead, I hope to help you think about the strength of wood in a different way.

First, I think we can agree that when we increase the thickness of a tenon, that it will be stronger. Right? So let’s say we have a 1/2”-thick tenon and we decide to double its thickness to 1”. Because we have doubled the thickness, that should double its strength. Right?

Wrong.

When we double the thickness of that 1/2” tenon, it can increase the strength of the component by four-fold or eight-fold. How much additional strength you get depends on the component – whether you are testing its “modulus of rupture” or its “shear strength” (this is covered in detail in the book – this is still not a commercial, I promise!). 

The bottom line is this: small increases in the size of components can increase their strength dramatically. This is hugely important when building chairs, stools, benches, workbenches or any object that will see abuse.

Let’s get back to this Hobbit-y chair for a moment. Cherry is weaker than oak. But if I increase the diameter of the leg tenons or the thickness of the seat by a mere 1/8”, I will more than make up for the difference between the two species. And the 1/8” added thickness isn’t really noticeable to the naked eye.

Take a look at these charts for some details.

These formulas are not my doing. They are created using the formulas from the “Wood Handbook” from the U.S. Department of Agriculture (a free download). For me, they help me design furniture that is strong without being bulky. I know that I can increase the thickness of a tenon by 1/8” and get a disproportionate increase in strength. I can do the math to prove it to myself. 

Or, as I discussed before, I can prove it with a sledgehammer.

— Christopher Schwarz

Wood for Stick Chairs

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WAIT, FROM THE LUMBERYARD?
You can build a stick chair with almost any wood. Yes, you can rive it from green wood. But you can also buy it at the lumberyard and get parts that are plenty strong enough.

Editor’s note: What follows is a short excerpt from “The Stick Chair Book,” which is scheduled to be released in hardcover form in early November. Until that date, you can buy an “Early Adopter Digital Package” of the book for $25. This digital package includes lots of extra goodies. When the hardcover book is released, this package will go away forever.

Most chairmakers are ridiculously worried about the wood they use in their chairs. Is it strong enough? Is it dry/wet enough? Is the grain straight enough? Can I get the parts I need from this chunk on my workbench?

But aside from those narrow concerns, there is a lot of flexibility when it comes to the wood you use to make a chair. The wood can be:

• almost any species
• air-dried, kiln-dried or vacuum-dried
• a softwood or hardwood
• sawn or riven
• ring-porous, semi-diffuse-porous or diffuse-porous
• from the lumberyard, the log yard or your backyard.

Put another way, almost any wood can be used in a chair as long as it is strong enough, dry enough and the right size. What follows is how to evaluate your stock in terms of its strength, moisture and size – without turning you into an intern at the Forest Products Laboratory.

TWO STICKS, ONE DISASTER
The stick at top has grain running its entire length. The one below has short grain and is doomed to snap. Training your eye to see short grain at a glance is a helpful skill.

Strength
Every stick of wood is a bundle of wood fibers. If the fibers run continuously from one end of the stick to the other, that stick will take far more abuse compared to a stick where some of the fibers run across the width of the board (sometimes called “short grain”).

You can create one of these super-strong sticks using a few methods. You can rive the wood – like firewood – so it splits along its long fibers. You can saw it out by following the direction of the fibers with your saw blade. Or you can use a combination of these two methods.

Neither method is magic. As long as the fibers run straight through the stick, you have done your job.
The other aspect of strength derives from the species of wood. A strong species, such as white oak, can be extraordinarily tough when it is only 1/2″ in diameter and its fibers run continuously from one end to the other. A similar stick of cherry or walnut might have to be 3/4″ in diameter (or larger) to possess equal strength.

While it sounds like I am about to offer a chart, graph or equation to determine the optimal-sized chair part, I’m not. Instead, I’m going to suggest you find a sledgehammer.

SLEDGEHAMMER TEST
When I make a chair, I make a few extra sticks and hit them with a sledge. I recommend it. You will learn a lot about how wood breaks and how some species (like ash) seem indestructible. Below are two victims. Short-grain walnut and brash cherry.

You can easily test a sample chair part by propping it up on two blocks of wood, one on either end of the stick. Hold the stick in place with one hand and strike the stick with a small sledgehammer (2 lbs. or 3 lbs. will do). If the stick survives the strike, the part is strong enough. If it snaps, you should increase the bulk of the stick or find one with straighter grain.

Why isn’t there a Holy Chart of Diameters and Species with recommendations for chairmaking? Because wood is so variable. For example: Slow-growth and fast-growth oak can be radically different when it comes to strength. (Slow-growth oak is far more porous and easily snapped.) How the tree grew, how it was dried and how straight you cut it all play a part in how strong a stick is. But one way to resolve all the variables is to hit a sample stick with the sledge.

The idea for this test came from fellow chairmaker Chris Williams, who was looking for a way to test wood for brashness – a defect where the wood is so brittle it can be snapped like a corn chip. It is also a method that the USDA Forest Products Laboratory has used to test brittle woods.

How hard should you hit the stick? Like you are striking a nail. Should you use a surviving stick in the chair after you hit it? It’s your call, but I usually use them.

— Christopher Schwarz

‘The Stick Chair Book’ Errata

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A reader named Jason Stick (he claims that’s his real name) pointed out an error in ‘The Stick Chair Book’ that I’d like to point out to you.

On page 494 of the chapter on the lowback, the text says the resultant angle for the front legs is 25°, and the resultant for the back legs is 28°. But in the drawings, the resultant is shown at 23° for both.

Here’s the good news: Either will work. Use the 23° resultant if you want to match the cherry lowback shown on the opening page of the chapter. Use 25° and 28° if you want a little more dramatic rake and splay to the legs. I used more drama when I built the first two prototypes of this chair, but then dialed it back for the final chair. I did this mostly so the resultants would match two other chairs in the book (for the sake of simplicity).

Shame on me for not catching this inconsistency, which will appear in the first edition. Bad Zoot!

Printer update: The book is due to ship from the printing plant’s dock on Nov. 5. We are fortunate that it’s Nov. 5 of this year and not next year.

— Christopher Schwarz

Learn to See With Your Pencil

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I think that writing a good song or designing a nice chair is a skill you can learn. 

The problem is that learning to write or design is not like memorizing the capitals of the 50 states. For me, that sort of rote learning is like gathering up a good collection of bottle caps and stashing them in a drawer.

Learning to design and write, on the other hand, is more like building a bottling machine when you’ve never even seen one before. You have to assemble lots of unfamiliar parts and get them working in concert.

One common piece of advice is to visit lots of other bottling plants to see how their machines work. In other words, listen to a lot of really good music to learn to write a song. Look at a lot of really beautiful pieces of furniture to learn to design your own pieces.

I give that piece of advice all the time. But it leaves out an important first step. You first need to learn to see and to listen. And learning to see or listen is damn hard. 

That’s because when we look at a piece of furniture or listen to the radio, our brain simplifies the stimulus into a single object or sound, when it really is a combination of a bunch of complex shapes and sounds.

How do you force yourself to see? Here’s how I do it.

It came by accident when I was working on “Campaign Furniture.” Many of the drawings in that book are tracings that I made of photos I’d taken in years prior. As I traced each piece, I was forced to examine the shape of every turning, moulding and component. I had to draw both the major forms and all the minor details. In other words, it forced my brain to stop seeing the whole piece and focus on all the small elements.

As I traced more than 100 pieces, I began to see obvious patterns. The handles of campaign chests were spaced above the centerline of each drawer. The stacking chests had drawers that refused to graduate (Fibonacci is a fibber). Sometimes the pieces got away with awkward drawer arrangements that looked dang good.

I also noticed so many little details. The best chests used drawer blades that were hidden – a detail I missed until I started drawing them. And I got a great feel for the beads and tapered cylinders that made up the feet of the chests.

So when I decided to stop copying old stick chairs and strike out on my own, my first step was to buy a pad of tracing paper at the grocery store. I then opened the enormous folder on my laptop of chairs that I love, picked the 50 best and printed them out. Then I began tracing them.

To be honest, once I started tracing chairs, it was difficult to stop. My pencil forced me to see so many things I had glossed over before. Chair shapes that I thought were complex were reduced to the squares, circles, rectangles and arcs I learned at Robin Wood Elementary.

I saw – for the first time – how certain elements were grouped together. Many beginners think that a design element should be carried throughout the entire piece. Matchy-matchy – like Garanimals. That’s how we got the California Roundover style, the nadir of furniture during my lifetime.

Instead, I learned how circles and rectangles worked together with the occasional irregular curve to make something that looks right.

I know, this is a boring and arduous way to learn design. There’s no Zen koan. Instead, it is a gradual revealing of the structure behind our world – one pencil stroke at a time.

— Christopher Schwarz

P.S. And if you want to learn to write a good song (and to learn to listen), try this.

Full-Size Chair Patterns Available (and Other Stuff)

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Folded printed plans for chairs inside a manila envelope on a workbench. Chair patterns sit next to the envelope.

When I think about the things I would grab from my shop during a fire, my chair patterns would be at the top of the list. The patterns I own have evolved during the last 18 years and began with some tracings I made during my first chair class.

These patterns are still my jumping-off point for all my existing and new chair designs.

In order to help readers of “The Stick Chair Book” begin their own collection of patterns, we’ve made five sheets of full-size patterns for all the major components in the five chairs in “The Stick Chair Book.” NOTE: If you have bought the Early Adopter Digital Package for this book, you already have these patterns in your possession. No need to buy them twice or thrice.

We are selling the patterns two ways.

For $20 plus shipping, you will receive five 22” x 34” sheets printed on lightweight paper used for architectural drawings. These can be easily cut out and stuck to thin plywood to make templates. The patterns include mortise locations for the legs and sticks. And the sightlines for drilling the leg mortises.

For $10 you can download a pdf of the five sheets, which you can get printed out at your local copy shop, reprographics firm or office supply store.

You can buy the patterns in our store here.

A couple other updates: We have restocked on Crucible Type 2 Dividers and have another big load on the way to the warehouse. 

Also, we were hoping to launch our Lost Art Press beer steins this week, but we hit a snag. We didn’t receive our full shipment of them. So we decided to hold off on launching them until we had our entire order. Stay tuned.

— Christopher Schwarz