Completed prototype in white oak with cushions by Renaissance Cushions.
Poul Jensen's Z Chair is an icon of mid-century modern design. But unlike a lot of modern furniture, this chair was designed for strength and comfort. Its a sophisticated form that uses simple parts and smart joinery. To my eye, its a timeless classic and a chair I think I would enjoy making 100 times over.
I eyeballed some photos and guessed at some of the angles. Joinery for the arms is nearly identical to a Maloof rocking chair. I scaled all of the parts from one dimension: the seat front rises 12" above the floor.
No fancy tools needed. Table saw, bandsaw, router, spokeshave, blockplane, screwdrivers, awl, rasps, fine-tooth saw, clamps, and forstner drill bits.
Here's Prototype #1:
The wood is recycled white oak flooring from our Idaho house and one wide board I bought from Second Chance, a local recycler. Loose tenon joinery is reinforced with epoxy, screws, and oak plugs. In all, there are 24 parts to this chair, plus 10 long screws and 10 half inch dowel-plugs. Each of the strapping pieces is about 32" long, attached with 72 pan head screws (nearly a whole box).
I found a roll of this 2" seat belt strapping on Ebay for cheap. Its tripled over, then screwed down. Hardware stores often have this stuff for sale by the foot. If you use screws like I have here, be fastidious about how you space and align them. An be neat about the folds as messy work will draw the eye immediately.
The seat frame is made of 8 parts and uses lap joints. The square frame sits in four 1/4" deep mortises cut into the inside faces of the leg assemblies. There is a horizontal cross rail (unseen) beneath the front edge that sits in blind mortises in the front legs. The head rest is through-tenoned and wedged.The arm-front leg joint is doweled blind and epoxied. Most of the frame parts are 1-3/8" thick. Feet taper to 1-1/8". The 3/4" diameter dowels for the backrest were tapered and fit with a spokeshave and wedged both top and bottom. Apply at least 3 coats of wipe on poly, then some paste wax once dry.
Mind the parallels, Josh Stockwell. Use the square edges and width of your stock to establish 3 important parallels, 1.) The seat back-to-long leg joint, 2.) the front leg-to-long leg joint, and 3.) he lower line of the long leg are parallel to the edge of your board. The rest is just straight tapers, shaped radii (start with Forstner bit holes), and bevel cuts at the back foot and long leg-to-arm joint. There's always some tweaking needed for each joint (a good block plane is one key to fitting chair joints well). Make and fit all joints in square stock - like Sam taught us - before you cut a single taper or reach for the router & roundover.
Measurements from first completed prototype (for Chad). I would keep most of these dimensions, but would probably tweak some of the joinery details.
A few more measurements from the completed prototype.
My initial notes made from photos I found online - educated guesses, really. Some of the rough part sizes were worked out during the prototype build. Other things were changed along the way as well.
A tip for the budget-minded chairmaker: The cost of new cushions may be several times more than all of the other materials combined. You might want to first locate some cushions and then size your chair to fit them. Or cut the foam down from larger blanks. Recycling the foam blanks from a not-too-worn-out sofa, replacing the batting wrapped around them, and having a local seamstress make zippered covers to fit will absolutely save you money. For comparison, quality custom made cushions for this chair will run $150-250 USD. That said, I really like the cushions Renaissance Cushions made me.
Now for the cushions and fabric. 3" foam for the seat, 2" for the back. Make sure its quality foam with firmness specifically for chair seats and chair backs. Maybe something like this?