Our church has an elevated area behind the altar and pulpits that is used to display banners and seasonal displays. They had some risers they used for displaying a nativity set at Christmas time. The original risers were made out of 3/4" particle board and 2 X 4's and 2 x 6's. Some were six feet long. They were all very heavy and took up a lot of room for storage. They were also very difficult to lift up 8 feet to the raised area and some were broken. The asked me to design something that would take up less space, be strong enough to support the weight of the large figures and be easy to handle.
At that time, I had been inspired by a torsion box design that Frank Pratt did. I put together a Sketchup drawing to show the committee what I was thinking of making for them. After a bit of back and for, I gave them an estimated cost for materials, which they approved. We finalized the design by settling on two foot and four foot lengths and how many of each.
Here is the completed set of risers. The panels have a frame that is made of select 2 x 4's cut to 1 x 1-1/2 with lap joint corners. The skins are 5mm plywood from the big box store and the foam insert came from the same place. The skins are glued to the wood with wood glue and the foam is glued with polyurethane glue that was spread over the entire surface. I weight tested the first one by placing 35 pounds on the center of the 4 foot span. The dial indicator under it deflected less that 0.01 inches. There are 8", 12" and 16" legs, which are all interchageable. I coated all the surfaces with 2 coats of oil based polyurethane to give the plywood some protection. There is also a storage box for all the legs that is not shown. The legs in the photo appear to be crooked, because they are not screwed all the way in....
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The committee is very pleased with the end result. The true test will come in December when they go to use them.