After a few classes understanding the basic mechanics of power tools, ergonomics, the dimensions of the human body, material characteristics, and the story they wanted to tell through their chair design, we settled on a hybrid cardboard/plywood form. The cardboard, as paper, represented their scholarship as students. This prototype was one of three proposed, the other two having mirrored single arms, so that the group of three chairs could be pushed together to make one couch-like structure, giving the user Options.
A comfortable, low-slung plywood frame cradles a soft, inviting cardboard seating surface, made of wheatpaste-laminated strips. We were in a bit of a hurry at the end of the semester, but with a little more care, one could also plug the screws with dowels, paint the frame, or make other aesthetic improvements. The end result is great to sit in, remarkably cheap, and easy to put together with basic tools. While we did use a chop saw and a table saw, partly for the sake of education, this whole project could be done with just some clamps, a circular saw, and a drill. We looked to some other Instructables for inspiration, including the Telephone Book Chair.
With all-recycled cardboard, wheatpaste that costs cents on the gallon, and cheap plywood scraps, this chair is lean, sustainable, handsome addition to the living room.
You will need these materials:
1 4' x 8' x 3/4" sheet of plywood
Scrap corrugated cardboard
1-1/4" drywall screws
2" drywall screws
4" drywall/deck screws
You will need these tools:
Step 1: Cardboardin'
My recipe for wheatpaste is simple: 1 part flour to 6 parts water. This is a little thin compared to other recipes, but it thickens as it cools. Boil a pot of salted water, reserving a small bowl of your total water to the side. The salt serves as a preservative. Whisk the flour into the small bowl of cold water, making a smooth flour/water concentrate. Once the water is boiling, whisk in your concentrate until well dissolved. Add a few teaspoons of sugar to enhance stickiness and continue whisking until the mixture returns to a boil. Turn off heat and let cool.
We made the laminated cardboard a few ways. One method is to cut strips of cardboard on the table saw, lay down your wheatpaste on each strip, and then put them together under clamps. Another method is to glue up sheets of cardboard, weight them down with plywood or similar, then cut them into strips later on the table saw. Make sure to alternate the "grain" of the cardboard, laying every other sheet with opposing corrugation for maximum strength and stability.
Once the wheatpaste has dried, cut the resultant strips (ours were 3" wide) on the chop saw. Set up a stop to get consistent lengths. The seat contains strips 20" long, and the back is 14" long.
Lastly, the strips need a rabbet so that they interface with the plywood frame. Clamp your strips together, aligning one end to a straightedge so they stay straight. Raise the table saw blade to 2-1/2", then run the clamped-together strips over the blade to create a groove of consistent depth. Finish off the rabbet with a box cutter, cutting back the strips.
Laminate the strips together permanently with wheatpaste, or wait until final assembly. Our design was 20" wide, yours may vary.
Step 2: Framin'
Use a pencil to lay out the silhouette of the chair. We made the seat start 16" off the ground, dropping 1" from front to back. It is 20" long. The back goes up about 18". We started at 90º off of the sloping seat, and then reclined it a further 15º for a nice, laid-back posture. Each frame member is 3" deep, the same as the laminated cardboard. The rear leg kicks out the same amount as the back, to prevent tipping over. We put a small taper on the legs for looks.
Use a circular saw to cut out the frame. Finish the tight internal corners with a handsaw. Use this as your "master", and trace it onto the plywood elsewhere and cut out a matching piece. Trace and cut out four legs, only, to reinforce the structure. Cut four 2-1/2" strips, 20" long for the cross-pieces.
Step 3: Assembly
Use 2" screws to put the 2-1/2" strips in, bracing the frame apart at four points. Put a dab of glue on each joint as well. The bottom of the strips should be aligned with the bottom of the seat frame and back. Use two screws per strip, pre-drilling each hole so the wood doesn't split.
Put the cardboard strips in, either as a block if you've pre-laminated with wheatpaste, or one at a time, putting glue between each layer. Once all in, pop a 4" screw in the center of each side to pull everything together.
Take a seat!