GeoShift Transforming Chair

I had my parts lasercut at Pagoda Arts in San Francisco, but an alternative option would be to print the file at full scale, tack the template to the hexacomb, and cut the parts out by hand. It is definitely a practice of patience, but I have done it this way before and I can say it is at the very least possible.

The chair is comprised of four sections, scored so that each of the four flat parts can be folded up into the four chunks of the chair. Make sure that you save the six circles that are cut from the center of the parts, you will glue these back in later to make the depression for the rotating joint.

You can see in the pictures that I also cut support structures for the inside of the chunks, but they didn't end up being necessary, this hexacomb cardboard is strong stuff!

The set up for gluing the pieces together it crucial, because there is a little bit of wiggle in the folded cardboard forms. What I did first was to line up the corresponding faces with holes that will eventually get the rotating joint. I did this by setting the faces together, then sticking one of the cutout circles halfway in so it was part way into both sides. This kept the holes aligned while everything was glued.

Next, tape the form together with blue tape to make sure everything is lining up, and that it sits flat on the ground.

Now comes the fun part, going hog wild with the old hot glue gun. The gluing doesn't have to be too clean, I was getting the full seam inside and out, nice and globby. You won't end up seeing either of these areas so aesthetics is of minimal importance.

I got super long glue sticks so I wouldn't have to reload as much, and it might also be wise to invest in a higher power hot glue gun. I kept having to take breaks because the tip would cool down from all the glue I was pushing through it.

Keep everything taped up while you glue and just shot around the tape, then take it off and touched up once it is all stable. Leave one flap open so you can come back through and run a bead along the inside of each seam for extra strength, or you can come through the side holes to touch up the inside, but it is a little tight.

At this point, the basic form is together and stable. It is now time to fill in the notched corners that result from bending in the 1" thick hexacomb cardboard. This is a four step process:

1. Filling in the round edges
2. Filling in the square edges. I chose to make sharp corners at any edge that touched another (See pictures for clarity) This makes the primary chair form appear more monolithic. Rounding all of the corners is certainly an option (and perhaps an easier one), it is just a matter of aesthetics.
3. Fill the edges with spray foam
4. Rounding and finishing the corners.

Filling in the Round Edges:

Since the cardboard is one inch thick, I used 2" diameter cardboard shipping tubes to finish all of the round edges. To fit the tube to each of the different angles, you follow these steps:

1. nest the tube into the edge
2. using the outside surfaces of the cardboard form as your straight edge, cut out a section of the tube
3. flip that piece over 180 degrees and it will fit over the notched corner to make a nice rounded edge.

(I have added the animated GIF above as I am finding the process difficult to describe)

As you finish each corner, cut it to the correct length of the corresponding edge, and hot glue it down into place. Be sure that the glue joint fills in the entire length of both edges. I would recommend coming in heavy with the hot glue and shaving the excess down afterword with a razor blade, just to be sure

Filling in the Square Edges:

In place of the cardboard tube, I used some scraps of 1/2" thick foamcore to fill in the square edges. I first cut a wide strip, then cut a v groove down the length of the center, leaving the paper on one side of the foamcore intact. You can then fold the length of the length of the strip in on the v groove and you have a clean sharp edge on the outside, all one continuous piece of folded paper. The process is similar to the tube at this point:

1. Set the angled foamcore into the edge you want to fill in
2. Scribe a line & cut off the excess material so it fits snug when flipped
3. Apply liberal amounts of hot glue.

Note that you may have to cut the v notch on the inside of the bend to be broader to match some of the tighter angled edges. This is a bit of a trial and error process, just make sure it matches up before it gets glued in.

Adding Foam:

Next, you get a big area prepped with newspapers/trashbags/biohazard containment equipment, basically anything you can gather to protect you and your property from the mess that is urethane foam (I seriously couldn't get the stuff off my hands for days. do wear gloves). You can buy this at any big box hardware store under the name "Great Stuff" (or an equivalent brand). it is spray foam that gets squirted into voids to fill them up and seal up your house, but it also works for squirting down cardboard tubes to add a little extra strength.

I was not able to photograph the process due to the mess, but you can see the open corner in the last picture where the tubes meet up. Just stick the Great Stuff tube in that end of the hole and squeeze the trigger until foam comes out of the other end of the tube. Do this at each corner, filling all of the edge tubes with foam, then set it and let it cure for a couple hours.

The foam expand as it dries, just let it balloon out at the corners and once it is cured, carve back the excess foam with a razor blade. There will be a lot of excess foam, but it comes off easy with a sharp blade once cured. Do your best to shape the foam at the corners to set just in from the final form of the rounded corner.

Rounding the corners:

Now that there is foam in the corners, you have a substrate to build up on. I applied a thick layer of hot glue onto the exposed foam at the corners, which makes a nice rubbery strong shell, with the foam underneath having a bit of give. This is important because the corners will be bumped often, so they need to be strong, but flexible.

use the hot glue to shape the corners to a smooth rounded partial sphere (or a square edge where needed), I used the hot tip of the glue gun to smooth down the surfaces of these corners and sculpt them into shape. Cut away any exposed foam that is preventing the hot glue shell from sticking to the surrounding cardboard tubes. This should be a strong connection, and no foam should be coming through the glue. Once the shape is pretty close, I did some final shaping by shaving down the hot glue corners with a razor blade.

Now begins the laborious process of the finish work. Go over all of the forms and fill in any voids with spackle, shave away any bulges, and repair any structural weaknesses. This mostly involved a lot of spackling the edges to hide the seams, coming back over lightly with sand paper to smooth it all out. I like to use the pink spackle that turns white once it is cured so I am not waiting any longer than I need to.

You can see in the last picture two of the corners that were sculpted in the previous step. The corner in the back needed an extra layer of spackle to get the shape correct, but the corner in the foreground is a thick layer of shaped hot glue. Nice and sturdy.

Next is the blocking for the Lazy Susan joint. Make sure you still have all of the cardboard disks that were cut out from the forms at the beginning. lay out the Lazy Susans from McMaster Carr on the cardboard circles and mark where all of the screw holes will need to be.

Find some scrap wood to add as structural blocking, I cut up some 1-1/2" square wood stakes from the garden section of the hardware store to be about 3" in length. Cut out a hole for the blocking at each screw hole location on your cardboard discs, and glu the blocking in flush to the face of the cardboard, letting the wood stick out of the back side. Apply a bunch of additional hot glue to the back of the cardboard disk around each wood block for added support. Now remark your screw holes using the Lazy Susans as a template (they should fall near the center of each block), and drill a 3/8" hole roughly 2-1/2" deep. Make sure the hole does not come through the back of the blocking, this hole will need epoxy to pool in it later without spilling out the back.

Set the circle with the wood blocking into the hole in the side of the form, and allow the circle to set in depressed from the face of the form. It should be depressed 1/2 of the thickness of the Lazy Susan so the forms touch eachother when they are ultimately put together. Use shims and tape to make sure this depression stays even while you glue in the circle.

To glue the circle into the side of the form, use the nose of the glue gun like a syringe to pump large amounts of hot glue into the openings in the edge of the cardboard where the circle is depressed. There will be cells exposed due to the structure of the cardboard, go from cell to cell filling them up with hot glue, down into the inside of where the cardboard edges meet up, until the cell won't take any more glue. It uses a lot of glue sticks, but it really welds the circle in there.

Take your pieces down to an open minded truck bed lining outfit, I took mine to A-1 Rhino Lining in Colma, CA. Jim helped me, he was excellent, here are some shots of him coating the forms. We started by attempting a white truck bed liner, but it wasn't going on as smoothly as the standard black. Ultimately, Jim and I made the call to go all black.

You are all set to finish this beast up! All we have to do now is install the Lazy Susans.

Bolt in your threaded rod to the Lazy Susans so they have 8 bolts sticking out, 4 on each side. Make sure they all spin freely, if the bolt heads are too big they may hit eachother. Go back over the holes in the blocking on your forms to make sure they are clear, then fill them full of epoxy resin (I used the 5 min stuff because I am impatient, but the 2 ton stuff might be a better option). Apply a bit more of the epoxy to the face of the circle, then squish your Lazy Suzan down into the holes, down onto the face of the depressed circle.

Repeat this process to add a lazy suzan to each of three forms, then do the epoxy on the rest of the forms and squish it all together making sure the forms line up. I used an extension cord to hold it all together overnight while the epoxy cured.

And you are done! You now own the least useful, but most fun chair on your block. Have fun swiveling the portions around and seeing how much not like furniture you can make it. Amaze your friends, wow your coworkers, impress that special someone. The world is yours with this most special chair, yours for the low low price of doing it yourself! (some material fees may apply ;P)

I exhibited this chair for three months in a public outdoor space, exposed to heat cold and moisture, and it held up even better than I was expecting! I took the photos above when I picked it up at the end of the exhibition, a bit dirty from the grass but in surprisingly good shape for cardboard, hot glue, and spackle.

This was a really fun project, thank you for sticking with my lengthy descriptions if you have made it this far.

All the best,

keep making stuff,

dswaim