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A gridshell is a structure with the shape and strength of a double curvature
shell, but made of a grid instead of a solid surface. The grid can be made
of any kind of material steel, aluminium, or even cardboard tubes - but the
Downland Gridshell is made of slender oak laths bent into shape.
To prepare the oak laths for use all defects were removed and the resulting
pieces finger-jointed together into standard lengths of 20 feet (6m). Six of
these pieces were then joined to form 120 foot (36m) laths.
The diagonal grid of laths was initially formed flat on top of a supporting
scaffold. The edges of the grid were then lowered gradually, and the grid
bent into shape, until the full shell was formed and secured to the edges of
the timber platform above the basement.
The grid is actually a double layer, with two laths in each direction. This
is necessary in order to combine the required degree of flexibility with
sufficient cross section for strength.
A fifth layer triangulates the grid to increase its stiffness. The laths are
connected at the nodes of the grid with a patented system of steel plates
and bolts.
The Downland Gridshell is one of a very small number of gridshell structures
in Britain, and its design and method of construction are unique. A very
high degree of carpentry skill went into its fabrication, emulating but not
imitating the traditional framed buildings at the Museum.
The workshop area enclosed by the gridshell is known as the Jerwood
Gridshell Space to reflect the Jerwood Foundation's generous support of this
unique building.
Further details and illustrations of the construction of the Downland
Gridshell can be found on the
Museum's
website.
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