AA Design + Make students construct an experimental lightweight tensile timber canopy in Dorset woodland
Generations of students at the Architectural Association have designed and built experimental timber structures at Hooke Park, the school’s woodland campus in Dorset. The latest is a sawmill shelter created by students on the Design + Make masters programme, En-Kai Kuo, Rolando Madrigal, Eleni McKirahan and Evgenia Spyridonos.
The tensile-timber canopy is intended as a ‘test-bed’ for the experimental prototyping of structural systems that will be deployed in the next planned construction at Hooke Park – a lecture hall and library.
“The main investigation was to test the limits of use of timber in tension in the form of an anticlastic surface that can resist both snow loads and wind uplift”, explain the designers. The timber net spans about 11 metres and is formed from 38 by 38mm laths of western red cedar, sourced from an adjacent stand of trees. To remove imperfections, the laths were assembled from shorter sections using a glued finger-jointed scarfed splice that was developed and tested at Hooke Park.
Ph: Evgenia Spyridonos
Each lath carries up to two tonnes of tension, “demonstrating the remarkable – and generally underexploited – strength of wood under tension”, note the designers.
The project draws on the spirit of earlier work conducted at Hooke Park, particularly the 1987 Prototype House designed by Frei Otto and Ahrends Burton Koralek, which uses roundwood spruce thinnings in tension to form the roof. Speculating that its innovative use of low-value timber and epoxy connections have further potential in lightweight timber construction, the Design + Make students proposed sought to test this in their own canopy.
Parallel research by student En-Kai Kuo explored the use of large-scale steam bending of whole trees. By slicing the end of tree trunks into laminas, steaming those laminas, and bending them around an adjustable bending jig a curve of 500mm to 1100mm radius could be formed in the 250mm-diameter logs. A set of 18 of these elements were used to support at one end of the canopy.
The roof surface is clad with aluminium sheet panels backed by CNC-patterned 6mm plywood, defined, fabricated and installed by the next cohort of students. The project was supported by tutors Martin Self, Emmanuel Vercruysse, Charley Brentnall and Zachary Mollica, with engineering consultancy by Arup and construction coordination by Edward Coe.
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