Building The Torso
Updated July 4, 2023
I have no experience at all with either fiberglass or mold-making. So of course I started by making a home-built robot torso! Inspired by B9 builder Mike Joyce's process, I decided to mold the upper and lower domes and the conical middle, then join them together. I also decided that the details like trim and front panel would be added afterward.
Starting Out - Molding
Ready to start making the upper dome mold. I started with a simple cardboard bowl shape and a homemade arm. I cut the upper and lower dome profiles out of steel and made them to attach to the arm.
The mold after several layers of premixed drywall compound. The first layers cracked a lot when they dried. But the last layers were thin and smooth.
The neon opening was then traced onto the drywall mold from a paper template and walled off prior to molding.
It actually turned out better than expected. I only roughed in the trim around the neon opening. It will be filled out later.
I did not use any mold release, though that would have made things easier. I think I sprayed gloss black paint on the drywall before molding, to little effect.
The bottom dome was done the same way as the top. Here I am building up areas for the vent openings. The smaller front opening is at the top of the photo.
I used masking tape and parts of a manila folder to wall off areas to add drywall compound. The more orange-looking circles are rolled up pieces of folder, used like little springs to push back against the weight of the drywall I was adding.
For the conical middle section, I took scraps of foam insulation and hot glued blocks along the outlines for the upper and lower edges of the funnel shape.
I hot glued polypropylene around the blocks.
As you can already tell, this is the wrong way around because the fiberglass should be added INSIDE the mold, not outside.
I decided to proceed to fiberglass the outside anyway and deal with smoothing it later. I had a lot of serious personal issues going on at the time and was not as focused on doing a good job as I should have been.
By the way, to make the tapered cone shape requires a slightly “rainbow-shaped” piece of plastic.
I made a super long drawing compass out of some boards for this. Not easy or precise, but it worked! It must have been something like 30 feet long and didn’t move easily.
It seems a bit "mental" to go to these lengths, but like I said, I had a lot of personal stuff going on at the time.
Here is the piece of polypropylene next to 2 yardsticks to show you the slight curvature.
I attached an acrylic plate to the top and bottom domes and connected them with threaded rod. This is only temporary until I finish connecting the 3 molded pieces with fiberglass. Then I can add the trim and the belly panel. I also cut the middle part so that I could make it match up better with the domes.
Continuing after Hiatus - Corrections & Major Details
The torso sat in this state for several years until I was able to work on it again. I discovered that it was not only crooked but the distance between the domes didn't match a profile template I had made. So I took the drastic step of cutting the top dome off to re-align and reattach it.
I cut pieces of plastic from the top edge of a tote and used them as brackets to hold the dome in position while I filled the gaps with Bondo Glass, a fiberglass-filled auto body filler.
The robot's front panel curvature should match the bottom of the conical part of the body so that it has the same radius all the way up instead of being tapered like the rest of the body. So I figured out what this radius is on my torso and cut foam board shapes to match. Then put a folder on top of it to make a mold. I used a sheet of baking parchment to keep the fiberglass from sticking.
The next steps were:
1. Add vertical foam strips inside the torso and fiberglass over them, creating support ribs.
2. Remove the support rods & acrylic plates.
3. Cut the opening for the chest panel.
4. Cut the large openings for the arm sockets.
5. Put the chest panel in place and start cutting holes for the lights and buttons.
It is finally starting to look like something!
In order to create the arm sockets, I hot-glued styrofoam panels inside the torso, using a level to make sure they were vertical. I then pinned the egg-shaped piece of folder to the styrofoam in a position where the distance from the front and side of the cutout were correct.
After pinning strips of folder around the "egg" and taping them to fit the cutout, I applied a generous layer of fiberglass resin before applying the first layer of fiberglass.
Note that the bottom of the neon opening is starting to be formed with epoxy putty. The plan at this point is to attach the rigid shape firmly to the torso and fill in the top. Once everything is in place, the styrofoam backing will be removed, along (hopefully) with the pins.
Here you can see some of the styrofoam support system inside the torso, as well as the start of trimwork around the neon opening using epoxy putty.