Making the Torso
The torso is made from a plywood frame covered in a couple plies of poster board. I chose poster board since it's relatively stiff but bends smoothly. Using something like a cardboard box wouldn't make a nice smooth curve around the frame as it would tend to crinkle at the corrugations.
The dimensions are somewhat important: too small and you won't be able to get into it; too large and you may not get through doors in your house (many inside doors are 24" wide). I settled on a top ring with a 20" outside diameter, tapering down to a bottom ring of 18". Each ring is ½" wide, which made it so that each ring nested perfectly within the next one, making for efficient cutting.
The torso height I chose is 25", although you might have to go a bit taller if you're a tall person. Four pieces of ¼" thick wood about 1" wide form the vertical struts that tie the rings together, and they're glued to the inside of the struts. A good thing about these dimensions is that standard 28x22" poster board fits nicely without requiring too many seams.
At the neck you need a ring with a 10" inside diameter to fit the head down inside. The head will eventually sink about 2" below that ring, and that provided the right depth (when the sonotube rested on my shoulders) so that I could see out the mesh mouth.
The 'shoulders' of Bender's torso are sloped upwards, so to get the angle I used a Dremel with a small drum sander attachment to sand out small angled reliefs in the top ring. I sanded out similar angles on the ends of the five supports that hold it in position. This way the supports ended up being flush at the outside perimeter of the top ring.
All wood parts were glued together using regular carpenter's glue, held together with normal spring clamps while drying. Everything else was a hot glue gun. I had no issues with the strength of any joints.
As noted above the skin was two layers of poster board glued together. Each layer is offset by half on the other layer, kinda like rows of bricks. I made it two layers because I wanted a bit more strength, and it would be easier to hide the joints since I would need three poster boards to get around the circumference.
The top/shoulder of the torso is similarly two plies of poster board glued together. I first cut out the rough dimensions, leaving about 2" of extra material on both the inside and outside diameters: an 8" hole in the middle, and about 22" (max width of the poster board) on the outside. Then I cut a slit from the outside to the inside, which enabled me to curve it into a shallow cone shape, kinda like one of those cones a dog gets when he comes home from the vet. Then I used the hot glue gun to glue it to the frame, starting at the slit/seam and slowly making my way around.
Once glued, I used a razor knife to trim it perfectly to the neck hole and outside frame.
The skin around the torso goes on pretty straightforwardly. The main thing is that you don't want one of the seams of the skin to be visible from the front, so you should start the skin close to where one of your arms will go. Conveniently, starting at one of the struts accomplishes this. Then just gradually roll and glue until you get to the end.
I cut the arms holes out after the skin was glued on. I made them slightly oval, to give enough room for the natural motion of your arms.
For the bezel around the arm holes, I used a single ply of poster board. With a bit of trial and error you'll get the size you need (a fabric seamstress's tape comes in handy for his build). Below you can see one finished bezel and one cut from the flat poster board before it's glued into the cone shape. If you look carefully you'll see that the flat cutout isn't a perfect circle shape; a perfect circle would make a cone that sits flat, but Bender is a cylinder, so by making it the shape you see here, it more closely conformed to Bender's cylinder when glued together. Then just hot glue it to Bender's body around the arm hole.
The last step is to place the head inside the torso. If you're using the sonotube to rest on your shoulders to support the entire body, you'll want to adjust its depth so that you can see clearly through Bender's mouth. Then hot glue it in place.
