I was asked to make a curved ramp to fit in with set designed by Neil Irish for the Theatre piece Eliza and the Swans.
The request was for a 0 to 2m high ramp that follows the curve of an arc across the surface of the stage. The arc angle needed to extend close to 210 degrees, with the inside radius x.m. The ramp was intended to be used at the Polsk Theatre, London and was designed to best fit the venues stage plan.
Use and tech specs
I needed to figure out the most efficient, modular construction method to fit these requirements.
The designed structure for this was formed by using a vertically rising helix curve and scaling this out from the central axis in the two dimensions across the horizontal plane. This created the width of the ramp and its path where the inside edge and the outside edge were level at the same angle formed on the horizontal plane around the axis.
I divided the ramp into sections at 36deg and maximised the width to best fit 8ft x 4ft ply sheets for the top surface.
The ramp structure is built from a combination of marine ply and spruce ply rather with no steel structure. By carefully fitting cuts into supplied sheet sizes, this material selection kept costs down and removed the need for cladding to create a clean smooth result, it also kept the fabrication within one department. To create the curved sections a double layer of either 9mm or 12mm ply was used.
The principle of this build method is to first create the second deck. This is the first complete 36degrees section, forms a straight forward curved block and simplest to build. It also provides a template to build all further sections from.
This section is made up from 6 rectangular cross-sections cut from 18mm spruce ply. These can be aligned on a marked out 2440mm x1220mm work panel. The curved walls can be easily measured and cut, with the top edges forming a straight line before bending. These are then rolled on and secured to the 18mm cross-sections.
The twin layered 12mm top surface can then be laid on as an uncut sheets one sheet at a time- bending it down, securing and trimmed with the aid of a router with a flush cutting bit.
The further sections can then be assembled on top of this base section. These sections follow a simple bearer and joist structure with the bearers follow the line of the helix and the joists bridging in a level line between. To do this, I temporarily secured steel angled section to the walls of section B and used clamps to hold the curved bearers in shape. The joist could then be slotted into position and fixed.