I've been active in the "Pearl Silver Laminate" thread, and thought this would be the appropriate forum to post some information about the rather unusual construction of our screen. For a variety of reasons, we opted for a 4:3 screen, made out of WilsonArt "Pearl Silver Crystal" laminate. We also wanted to make the screen adjustable from a torus (required for our current stone-age projector), to flat (if the old dinosaur dies, or if someone donates a better PJ!
I've stolen a lot of great ideas from this group, and I really appreciate the depth of knowlege available in the AVS forum.
The first interesting fact is that the "four-foot by eight-foot" sheet of laminate actually measured closer to 49 1/4 x 97 1/4 inches! I'm guessing that's so in case the edges get chipped in shipping, the customer can still get a 48"x96" sheet out of it. We cut ours to 48 3/4" x 64 3/4", which we planned to leave a 1/8" clearance all the way around, inside our frame. We first 'rough cut' the sheet with laminate snips, then cut it to final size with a router. Here's a photo of the cut sheet -
We made a frame out of nominal 1"x4" poplar (actually 3/4" x 3 1/2"). We used half-lap joints made on the tablesaw for the corners, and reinforced them with triangles cut from the poplar- raised 1/4" above, and set into the back of the frame- which will also support the back of the screen when in 'flat' configuration. (photos below). The frame is 50 1/2" x 66 1/2" outside measure, and 49" x 65" inside dimensions. We used "Titebond III" wood glue for all wood joints. Here's a shot of one of the corners-
We then made a vertical 'crossbar assembly' out of nominal 1"x2" red oak (actually 3/4" x 1 1/2"), again with half-lap joints, and glued and screwed it to the back of the frame. This will be the attachment point for the mounting plate described and pictured below. Here's a shot of the assembled frame-
After running the numbers for a torus, we decided to fudge just a little. We cut four corner blocks 2 1/4" high, at an 83 degree slope to support the corners of the screen above the rear of the frame- for the 'torus' configuration. These blocks are screwed-in, but not glued, so they can be removed. Again, a photo of the blocks is below-
We attached 'cleats' at each corner, and at the center of each board, to rear-mount a velvet-covered 'picture frame'.
Lastly, we made a 'mounting plate' for the center of the finished screen. This was a piece of 24" x 32" (very nice, silver-coated) pegboard, with the corners cut off at 6" in (to allow the outside corners of the screen to flex smoothly). We made a cross-shaped brace (1"x2" poplar and half-laps, again...), and glued and screwed it to the 'rough side' of the pegboard mounting plate. This makes for a flatter center than a perfect torus, but not by much- the ideal screen torus for our setup curves very
little at the center-- and we needed enough surface area for a good bond with the contact cement. Here is a photo of the rear of the completed 'mounting plate', showing the crossbrace-
Then we ground down the screw heads and any 'stress-swollen' masonite around the screwheads. After grinding, they were filled with "JB Kwik" epoxy, and sanded flat again (I've worked with laminate in the past, and it 'telegraphs' things like screwheads somethin' awful....). Here's the 'face' of the mounting plate, with the epoxy covering the screwheads-
After thoroughly cleaning and drying both the pegboard and the back of screen, we masked-off the area on the back of the screen where the mounting-plate was to be affixed. Using a roller, we applied two coats of contact cement (solvent-based) onto both the masked-off area of the screen, and on the entire 'smooth-side' of the pegboard, according to the directions on the can.
We peeled off the masking tape, and affixed the pegboard to the screen (with contact cement, you get exactly ONE chance at this!). We used a "J-roller", and then for good measure, a wood block and hammer (it wants 75 pounds per square inch for proper adhesion). This stuff adheres instantly, but doesn't achieve full strength for 7 days, so we then left it alone for a week- it'll be under some
stress, so we let it rest. Here is the rear of the screen, with the pegboard mounting plate attached-
We've made a "picture frame", mitered at the corners, with an inside diameter of 48" x 64" (od= 55" x 71"), also made of the nominal 1x4 poplar. One of the guys is covering it with the black velvet we got. We'll also be using the black velvet on the inside of the frame. In both cases we'll be using 3M 77 multipurpose spray adhesive to hold the stuff on. Finally, everything will get a coat of 'Rust-O-Leum satin black applied with a foam brush.
I just 'dropped-in' the screen assembly to take these next photos--
Screen in 'flat' configuration-
Screen in 'torus' configuration-
We haven't "pinned-down" the corners yet, so these photos were all taken with the laminate just 'laying' on the frame. The curves are exactly what we were hoping. I'll get some more photos as we continue to assemble and test this thing!