As you can see from the picture below, the star ceiling will sit flush with the bottom of the sheetrock. We left 1&1/2" above the foam for clearance of the fiber optic strands. The extra 1/2" from the drywall gave a solid 2", plus a little more in some areas with the cavity in the floor joists. After running some of the fiber optics, 2" is more than enough space.
One item I neglected to mention earlier is that the projector will end up being mounted in the star ceiling. I needed to determine the depth and size for the blocking, and I had initially marked a few stars where the projector was going to sit, so those needed to get moved:
Here we are looking at some trim options for once the panel is permanently installed:
Once we had the projector mount centered, we were able to determine the size of the blocking to house a conduit for the HDMI cable, and have an outlet box included. You can see in the below photo there was a little sag in the 1&1/2" foam board, so we installed 1/2" plywood around the perimeter of the blocking that we can screw the foam board into if necessary. At this point we still hadn't attached boards to the back of the foam panels to lock them together yet.
Firming things up was the next order of business. I purchased 2 1"X6' plank boards to use to bolt the foam boards together. With the use of 3" bolts, large washers on the foam side and nuts with lock washers on the board side, we were able to secure the foam boards together. It pulled the seams together tight, although there was still a little bit showing. My dilemma was, risk sanding them smooth and have a rogue sander make mince meat of my foam board, or leave the very slight seam and hope that the fabric hides it. I elected to trust the fabric to hide the seam, we'll see if that pays off in the future.
Another item I didn't mention before was drilling the holes in the foam for the stars. I used the smallest drill bit I could find with 3" of length to drill the holes. The drill really wanted to wander when it touched the foam, so it took a steady hand, and I found that higher RPM of the drill resulted in less wandering of the bit before it began to sink it. Care needs to be taken not to press too hard and end up with divets in the foam. I drilled from the viewing side, so I really took care not to make any dents or imprints on this end of the foam. I had lightly tightened the plank boards onto the foam panels and was able to locate the holes needed for the fiber optics by the small imprint from drilling through the foam. Once I was done drilling all the holes, I removed the boards, and drilled larger holes to feed the fiber optics through:
I found a 75" wide polyester fabric at JoAnn's that looked like it would be perfect for this project. I purchased 12' for around 30 bucks if I recall correctly. Now that all the holes were drilled, it was time to apply the fabric to the foam boards. First main regret, I should have painted the 2X6 boards while the panel was apart, or at the very least before the fabric was applied. I made it work after the fact, but it would have been much easier, and cleaner, if I would have done so sooner. Not much of the 2X6 will be visible, but enough of it will that I wanted to make sure it was blackened out.
First order of business, tighten the bolts to recess them into the foam panel. We did a couple of tests on a scrap piece of foam using a forstener bit, but in the end we found it wasn't needed and we could just simply tighten the bolts and recess the washers and bolt heads into the foam. My brother is one handed at the moment due to a pinky injury that went from bad to worse. His pinky is currently attached to his chest for a skin graft, but he still has one good working hand, so I put his butt to work.
We thought about using a filler for the bolt heads, but decided to leave the holes blank and let the tension of the fabric do its magic. It was a chance, but it worked out well and we weren't able to see the 12 holes (6 per board). We laid the fabric down and disconnected two ends of the panel to separate the foam boards in order to wrap the fabric:
Here is our sticky stuff. One can worked out well to get the entire center of the fabric and the foam sprayed, but it did not leave any for the sides. By design, we had made this a very tight fit, so ultimately I don't feel we needed the adhesive on the sides, but it would have been a nice insurance, and may have helped hold the fabric better while we were trying to reassemble the entire panel:
I gave Jeremy the honors of applying the Super 77. He sprayed the fabric, then the foam and we waited a couple of minutes for it to get tacky to the touch. Once it was tacky, my brother, Jon, held up one end and my wife came down to hold up the other end. Jeremy and I worked the fabric from the center to the edge with our hands to apply it smooth onto the board. We kept a slow and steady pace, and it was really going on well. We had to keep very consistent or the fabric would start to wander to one side. This happened on the first half, and I believe it was due to either my wife or Jon pulling a little harder on the fabric. Luckily there was enough slack to keep enough of a flap to go completely into the channel for putting the panel back together. The second side went much smoother as we had a little experience from the first side. It only took a minute or so for the fabric to be set onto the foam, and it wasn't going to go anywhere.
We all put a quick signature on the top of the panel and put it up on the saw horses for me to start the final work:
Shortly after, I wrapped up sheetrocking the theater, and my mudder/painter was to begin the next day. He was going to be 10 days or so to finish up, so that was my timeline to work on the star ceiling and get it finished up: