The college where I work has several of these wonderful Model 3107 plywood chairs designed by Arne Jacobsen. Our local symphony orchestra uses them when they perform in our campus theatre. When the chairs are not in use, they are usually stowed away for safekeeping. But recently, a few have somehow found their way into a classroom or two where they have come to a bad end. A couple of weeks ago I saw one broken in half and lying on a pile of trash bags. Well, I couldn't let it be tossed away, so I grabbed it to see if I could somehow save it.
Step 1: Assessing the Damage
I removed the frame from the seat of the chair. The tubular frame is attached to the chair seat with three screws and the screw plate is covered with a plastic cap. Easy stuff to do. The frame looked pretty good but as you can see the plywood edge is pretty ragged.
Step 2: Repairing the Damage
First thing I did was to glue the plywood, where it had started to split, back together. I used Elmer's Wood Glue. I wedged the splits open with a scraper and forced glue into the seams. Then I clamped the whole thing together and let it set for 24 hours.
Step 3: Cutting a Curved Back
Next, I decided to trim up the edge. I traced the existing curves of the chair seat onto a sheet of paper and modified it until it looked good. I transferred the curve onto the front and back of the chair. The front so that I could see what it would look like and the back because I would need to cut the curve from the underside of the seat. I used a jigsaw for this part. Sorry, no shots of the cutting.