To net or not to net - 3rd edition - Department of Primary Industries

Figure 20. 12 mm quad hail net
Net colour
hail is possible. The tighter the stitch density, the more expensive
the net and the structure required to support it.
One indicator of the strength of a net is the weight per square metre
(remember to compare nets of the same mesh size). Another is the
thickness of the monofilament fibres, which is measured in ‘denier’.
More light is intercepted by heavier, stronger nets and they have a
greater impact on the orchard microclimate than lighter nets made
from thinner monofilaments; however, lighter nets probably will not
last as long as heavier nets. Lightweight vine net may have a weight
of around 30 g/m 2 , while a 12 mm quad net typically weighs about
90 g/m 2 .
In the past, other types of net have been used to protect orchards.
These nets may still be available, but they are not as suitable as
knitted nets for orchard netting. Extruded nets consist of a grid of
extruded plastic. Extruded nets are cheap, but not as strong as
knitted nets, and do not last as long. Knotted nets are made from
monofilaments twisted together to form multifilament strands
(rope), which are knotted together to form a square mesh net
with a knot at each corner. Knotted nets are heavy and relatively
expensive. Knotted nets are better than extruded nets but not as
good as knitted nets.
Traditionally, white nets were cheaper than black nets but had a life expectancy about two-thirds of black
nets, which used carbon black as a UV stabiliser and had the best durability. However, modern white nets
incorporate chemical UV stabilisers that do not colour the material and have comparable life spans to
black nets.
Prices are now the same or very similar for either black or white nets. White nets tend to ‘bounce’ light
through the mesh and reduce light levels less than black nets with equivalent mesh size. Grey nets with
properties intermediate to white and black nets are also available from some suppliers.
Net width
Net panel widths should coincide, if at all possible, with tree row widths or multiples of these. Panels
are usually 10–15 m wide but can be specially manufactured to any width up to 50 m. Wider nets are
generally favoured where available as they reduce installation costs because there is less joining;
however, very wide nets can be difficult to handle when erecting.
Generally speaking, a good way to determine a net’s optimum width for handling is to convert the mesh
size in millimetres (not including any cross-stitch) to metres (e.g. a quad net with 12 mm mesh is best
hung using 12 m wide net). With flat canopy designs, panel widths greater than 10 m may require a
support wire down the centre of the panel to reduce sag.
Doors
Plan the position of doors carefully for efficient access. Doors can be as simple as a curtain drop of net
with a pipe weight at the bottom. A more elaborate hinged-gate design, consisting of a metal frame
covered with the net material, can also be used.
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To net or not to net