My father-in-law has been a long-time builder of Adirondack chairs. He’s retiring this year, so I decided to build him a custom Adirondack chair for his retirement. I looked around a bit for inspiration, and really liked this chair by Michael Brown:
The lines are nice, and I like the idea of the bentwood slats for the back and seat, to be more comfortable than the traditional Adirondack design. I posted a question about it on one of the forums, and Andrew Kopac of 24HourDesign.co was kind enough to contact me and offer to put together a design based on the photo:
Andrew did a couple of iterations with me to adjust some of the features and did a really great job. I recommend him if you’re looking for someone to put together a design!
I had a general notion for the profiles of the chair and back slats, but I was a little concerned about the exact dimensions. I ended up ordering rocking chair plans (and the book) from Hal Taylor's Rocking Chair University. I was able to make a template for the back slates more-or-less directly from Hal’s plans. Hal’s rocking chairs have carved seats, so there isn’t a profile in the plan, but I put one together based upon the general dimensions and it turned out to be very comfortable.
I originally intended to make laminated slats, but since I wasn’t too confident in my ability to resaw a bunch of 1/8” plies I decided to try steam-bending the slats. I purchased a steam bending kit from Rockler and put together a steam box. Embedding videos doesn’t seem to be working, but if you care to follow the link here it is, quietly percolating away:
As you might be able to tell from that video, I built the steam box out of 1/2” pine, which turned out to be a bad idea. The steam started warping and destroying the box pretty quickly. After a few uses I had to build a new box. This time I used 1/2” plywood and finished the inside with spar varnish. The second box has held up much better, although the plywood has started to delaminate at the door end where it is more exposed to the steam.
I also took a couple of tries to settle on workable bending jigs. I initially tried to create a jig with dowels at the key bending points. This actually worked very well, but the pressure on the dowels ended up denting the wood. So I ended up building more complete forms for the bending jigs. As it happens, they fit nicely on a standard 2×4:
As you might guess from that picture, I initially made the forms from 2×4 stock, but they turned out to not quite be tall enough for the slats I was using. (I used 1/2” craft slats I could get pre-cut at a Big Box Lumber Store. They are 2.5” wide. For the final chair, I’ll probably do 2” slats.) So I had to add another layer of plywood to each of the bending blocks.
Pine is apparently not the best wood for steam bending, but after 8 seat slats and 8 back slats I got pretty good at bending. So steam bending looks like it will work for the final chair, but it’s clear that it will be important to be very consistent, otherwise the slats don’t match up well when placed side-by-side.
Based upon Andrew’s design, some of the comments on the forums and some of my own ideas I put together a mock-up in pine. I wanted to do a mock up so that I could play around with the seat and backrest angles, the height of the chair, the geometry of the arm-rests and so on. This was a good idea, as my initial seat angle was too steep and the back had to be much more upright than I expected. Here’s what the mock up looks like:
As you can see, the mock-up has adjustable arms. The back pivots on dowels at the bottom, and by changing holes on the front of each arm I can adjust the angle of the back. As you can see from the number of adjustment holes, my initial guess was pretty far off!
I’m pretty happy with the fit of the mock-up. I was a little worried that the back wouldn’t be sturdy enough made out of 3/8” thick slats and anchored very low, but it turned out to be quite solid. It flexes enough to be very comfortable. It isn’t obvious in the above picture, but both the seat and the back are dished. The seat is dished 1/2” over 22”. The back starts the same and ends up dished 1” over 23” at the top. (The back fans out slightly.) For the final chair I may increase the amount of dish.
The next challenge will be to do the arms. They need to be flat at the front (i.e., to hold a drink), slant backwards for comfort, and then slant again to fit to the cross-piece on the back.