Theatre Design & Technology - Winter 1980 - 16

The Ride Across Lake Constance
The design, again by Roos, was based on a movie palace metaphor, with a long double staircase converging on a central landing
and then spilling down centerstage. The two converging staircases
had to cantilever from the central landing and needed to be finished
underneath. The lower portion of the stair unit was conventionally
constructed (Fig. 8).
The cantilever structure stretched the working-drawing's processdescription (Fig. 9). The drawing revealed an 18' cantilever over the
floor while showing that the two wings of the upper staircases did not
meet at a straight angle.
Dropping the front rise and rear rise for each step from the floor
plan and then drawing in the scaled treads placed the rise/tread progression for the step unit. Under this almost French-curve progression was drawn the curvature for the underside of the cantilever. Paralleling two imaginary lines inside the stair structure and either side of
a center line for the cantilever placed forming jigs within the drawing.
These jigs could then be abstracted for a structural drawing.
The two skins were 112" ply and the lamination was 8" thick, consistent with the rise of the treads within the set and the necessary thickness of the upper platforms. Two legs were laminated into this sandwich, which emerged from the end to become bottom. As both side
staircase cantilevers converged at an angle, and as the distance between the laminations was insufficient to bring the lamination to the
floor without crossing each other on the upstage side, the legs allowed placement flexibility without a difficult drafting solution involving the lines along which the laminations might meet under the
center platform. The core material was notched to place the legs
emerging from the lower straight portion of the formation.

Figure 8: The Ride Across Lake Constance, designer's model. The two
upper platforms are 8' above Ihe stage floor and represent a cantilever of
about 22" (curved beam length).

r---r-'·-------+----+---i

Both the lower portion of the lamination which would back the
stairs, and the upper end of the lamination which would form the upper platform were straight. For the curved portion between, 'I." plywood was laminated into the forming jig. The 'I." sheeting was staggered for binding to become 112" thick, while the 112" ply sheets on
either end of this bent section were attached by glued and screwed
plywood laps (Fig. 10).
First one plywood surface was placed onto the forming jigs and
joined. Then, after the application of white glue, core material was
stretched and laid onto the sheeting after having been notched where
appropriate. The upper surface of the lamination was then placed,
again using curvable 'I." ply to form a consistent 112" surface fiber.
After about four days of curing time, the jigs were removed and the
weights taken off of the laminations. The "wings" were turned over
and raised into position for placement either side of the center landing
unit. Treads were then attached, using custom fitting procedures.
With the onstage edge shapes being translated directly from the plan
view, only the sheet edges meeting the lamination needed to be cut to
fit.
The central portion of any honeycomb lamination is stronger than
the edges because the weight applied to the surface radiates in all directions. When a load is applied nearer the edges, the load distribution can only radiate up to about 180 0 * This sandwich edge is called
the close-out, as the sandwich must be closed with facing. In this unit
the close-out facing was to protrude above the edge considerably,
both upstage and downstage, with the front-edge masonite forming
the railing. When the designer removed the upstage protruding facing
and left only the distance between the surfaces to serve as the closeout space, apprehension grew--but the unit carried without a problem.

Figure 9b: Working drawing for the structuring forming jigs. The drawing
does not detail the actual jig structure, but only grids the curved portion of
the lamination and indicates the lengths necessary for the jig.

Figure 9a: Working drawing used to layout the lamination for the cantilevered platforms. The master drawing used the right half of the symmetrical floor plan to drop a front elevation based on the rise/tread ascent of
the front and rear edges of the shaped staircase. Locating the sheeting on
the plan view could then provide angfes for the projected jigs to form the
lamination.

Figure 10: Surface sheeting of ~" and laminated ~" plywood lying on
the forming jigs. After framing and spacing the jigs, the bottom lamination
surface was edge-joined. The top sheeting was done similarly after the
core material was laid down with glue. The whole lamination was formed
and weighted at the same time to save two drying times for core adhesion.

Table of Contents for the Digital Edition of Theatre Design & Technology - Winter 1980