The next morning, I was happy to see the balloon was still in shape, so I begin cutting paper for another coat, when from my kitchen table I heard the loud "pow!" of failure.
This attempt, too, failed. The balloon burst, probably trying to expand with the heat of the day into the rigid shell of the dried paper mache. The entire thing just crumpled up into a big ball of crinkling failure as the latex tried to contract around the dry paper mache. It sounded like popcorn and smelled like tears.
Time for Some Pragmatism
it is at this juncture, that I decided to stop trying to build the Dome structure, myself.
On my desk, a stack of Home Depot, Lowes & Amazon receipts totaling several hundred dollars, including $175 in just big silly balloons.
Add on copious quantities of fiberglass @ $30/gallon, 4 gallons of StyroSpray at $70/Gallon, 3 gallons of Elmers Glue @ $15/gallon, $20 in Sunday newspapers, PVC, wood and other materials, my attempts to do this on the cheap started to really stack up to be not-so-cheap-anymore.
All this investment (not to mention time) and I had very little to show for my efforts. Plus, my wife really wanted the garage back. :)
It was time to just go buy a dome (besides there are plenty of other components needing to be built to finish out the project.)
Along the way I had been talking to everyone you can imagine, trying to source a dome structure. I tried everything I could reasonably think of and many sources suggested by smarter folks. It still seems like there HAS to be a low-tech plasticky (or other) dome structure out there that could be repurposed for this.
I tried spas/ tubs, koi pond parts, custom aquariums, fire pit inserts and lids, farming silos, industrial tanks, cut-down propane tanks, playground parts, skylights and various plastics and acrylics suppliers. I went to three scrap yards and talked to all sorts of people who gave me weird looks when I tried to explain what I was looking for.
I talked to every plastics and acrylics fabricator and many-many fiberglass fab shops within a 200 mile radius. A few could do it but needed to build a form, first. That cost ranged from $1400 up to $85,000 depending on who I talked to. They would basically CNC, cut circles of plywood until they built out the 6 ft dome of stacked plywood. Then, lay fiberglass or melt down plastics over top of it.
Many responders were downright discouraging with snarky comments like "6ft?! What the heck are you building over there, a rocket?"
Yes, I'm ordering the equivalent of a 6 foot rubbermaid trash can lid, it MUST be rocket science.. :)
Sourcing a Dome
If you want a dome made, here are your options (at least from what I've found).
You can reach out to local fabricators. Two options I've found are Fiberglass or Acrylic.
The Fiberglass folks need a good mold to work with. If they build you a mold, the average cost of a CNC-cut mold is going to be about $3500. Each dome from that mold will cost about $1500. Unless you find a fiberglass shop that happens to have a giant round ball sitting around.
For Acrylics, I've found that many shops simply do not have an oven large enough to heat that large of a sheet. 69" Diameter is about as large as most can do to limitations in either material availability or oven size.
In the Acrylics-Plastics side of things, you are looking for a thermo-molding fabricator. Ideally, someone that already has a round mold to work with or has some other ability to mold plastics, such as vacuum-forming or free-blowing.
If you aren't going with a local fabricator, there are a few places online that sell domes for skylights, buildings, churches, etc.
These guys make them:
http://www.eztopsworldwide.com/domes.htm
Their prices are really fair. Sadly, shipping costs as much (more, actually) as the dome. I almost ordered from them but I was concerned that when I got the dome home and tried to cut the plane / truncation out - I may crack or otherwise damage the acryllic.
I really wanted a full-service shop to just do all of that cutting for me.
