Redryder asked about the steam-bending process. I’ve covered that a little bit earlier in the series, but I bent the arms (well, one so far) today, so I took some photos along the way.
Here’s the basic set-up. The box is made out of plywood, dado-ed, glued together and caulked on the seams. It has held up fairly well but is starting to come apart in some places and I’ve had to reinforce it. The steamer is the standard Rockler kit. The kit comes with the brass fitting to hook the hose to the steam box.
Here’s the bending jig for the arms. For this project, I found that I could use a one-sided form and I didn’t need strapping. This jig has to be pretty tall because the arms are mirror images but bend the same way, so the jig has to accommodate an arm facing either way. Notice the rounding on the bending corners to reduce the stress when bending. For reference, here’s an arm on the jig:
No action photos of this next part because it is time-critical. After the piece has been steaming sufficiently long (recommended 1 hour per inch) you pull it out of the steamer (with gloves!) and quickly bend it onto the jig. It ends up like this:
(The blue painter’s tape is there to remind me which side is the top so that I bend it the right way!) What’s key to the bending is the heat—it loosens the lignin bonds in the wood and let’s it be reshaped. The fact that steam is wet is actually irrelevant—steam just happens to be a good way to move heat around.
This view shows that the arm ends up in a graceful curve. If I had wanted sharper bends and a flat middle section, I would have needed a more complex jig (like the one for the back slats).
I find that leaving the piece on the jig for 24 hours yields the most consistent results. If the result isn’t quite right, I’ll re-steam and re-bend. The wood is more pliable on subsequent steamings.