For Once Upon a Mattress we built a set of spiral stairs. As with most things built for theater, the stairs were not built as one would build a set for a house.
You can see the lighting boom on the floor.

Holes were drilled in 2x8 lumber and placed on the boom. Wood spacers are separating each step support. The boom is the center of the circle. n2.jpg
You can see additional spacers holding the steps apart; further away from the center. Once we are done building, you'll see that the steps protrude out of the castle tower. These were latter changed to a 2x10 stringer. n3.jpg
We stacked the treads and inserted the pipe through a hole in both the top and bottom platforms. After the pipe was guided down to the floor, we placed spacers near the pipe in between each tread.
We've installed a stringer to support the treads near the middle of the treadsn6.jpg n5.jpg
Curved Plywood! Yup, curved... We made this ourselves. Several 9" wide strips of 1/8" plywood are glued & screwed together in the shape needed. Once the glue dries, the curve is very strong.n8.jpg n7.jpg
Jeff & Christina test our stairs. You can see the clamps that held the plywood together while the glue dried. n9.jpg
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