Here is the finished cherry, butternut and hickory rocker that I have been building. The design and construction had a lot of interesting lessons that I plan to take forward into new work.
Here is where the design of the back began. I used my student Stacy to test out the curve of the spindles, which I cut into a 4 inch thick chunk of pine left over from my timberframing (I will get back to that soon!). By notching the back of a dummy seat and clamping the rig to my shave horse, I was able to adjust both the curvature of the bend and the relationship between the back and the seat. Also, by slipping a wedge under the seat, I was able to adjust the tilt of the chair. It worked out great and I based all of my curves and angles on it.
Here is the bending jig that I used to bend 8 spindles (one extra!). It worked out nicely.
Here are some more images of the finished chair. It is very comfortable. I had a variety of folks sit in it at the Narrowsburg Riverfest on Sunday and got uniformly positive reviews. I plan to delve even further into the physics of rocking and comfort on the next chair. I also played with the spread and splay of the front legs to balance out the large and shapely top.
My next rocker will be all white oak with a butternut seat. I plan to fume the whole finished piece in ammonia to darken the oak. I've done this before on tables and small kitchen pieces and love the results. I am also adjusting the design to make it possible to finish nearly all of the surfaces with a spokeshave, I have seen too much of my old nemesis sandpaper lately. Next week brings a new student into the shop, so I'd better get out there and get my personal fussing overwith!