There has been some discussion lately about building domes, I thought I would toss my two cents in. First Disclaimer, I have not built a dome using this method, but some basic experiments on the technique look promising.
Start with purchasing the 4' x 8' sheets of 1" EPS foam insulation (typically pink or blue).
Cut out your gores (using Ron's formula).
Build a simple jig to hold two of the gore sections bent to the correct radius with their edges in contact with each other.
Apply either 3" fiberglass tape or two layers of Henry 296 roof patching tape.
Coat the tape from above with either Epoxy (not available at Home Depot) or Minwax Polycrylic water base clear finish (more discussion below).
After the coating is dry, fill the V shaped gap on the back side where the gores are touching with Great Stuff foam.
Repeat to add additional gores. Perhaps build sections of multiple gores that you can bolt together (requires a flange bonded to the edges with epoxy and filler).
For an indoor dome, just paint. For an outdoor dome, cover with a layer of fiberglas mat and a layer of fiberglas cloth, then paint.
NOTE - You can NOT use the fiberglass resin that is sold at Home Depot for this project, it will melt the foam. You have to use either epoxy (expensive) or Minwax Polycrylic (not cheap, but half the cost of epoxy).
Attached are photos of the Minwax, the Henry repair tape and a test foam piece I made.
My experiments indicate that the Minwax has roughly the same peel strength of epoxy with a failure mode of peeling the top surface of foam off.
The test piece was edge glued together using Gorilla Glue for foam. I believe that it would be very difficult to maintain an even enough bevel to allow a consistend foam to foam glue line, hence I would just cut the gores sides square and then fill the resulting gap with Great Stuff.
As I said, I have not made a dome this way yet, but intend to replace my 10' cloth dome with a 12' foam dome "sometime". Obviously it would be smart to build just a couple of gores this way before committing a bunch of $$ to raw materials.
I have build props using these methods do I am highly convinced that a dome can be successfully build this way. Anyone up for the challenge?
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