Redpath Cosecant Curved Rafter
Condensation Safe Ridge:
Redpath is leading greenhouse design with a range
of innovative features to optimize growing conditions and reduce risk of
crop failure. The innovative technology of the cosecant curved rafter
and raised ridge options have minimized the condensation drip in both single
and twin skin structures.
In the single skin straight rafter buildings it
is not possible to keep sufficient tension on the plastic to prevent
the plastic from flapping and causing the condensation to be flicked on
to the crop beneath before it can run off the film and into the gutters.
Latterly the use of twin skin inflated plastic on straight rafter structures
has exacerbated the problem of condensation drip as the lower skin of plastic
of the twin skin (double-poly) structure is pushed downwards by the air
pressure between the skins causing a greater reduction in the pitch angle
of the plastic. The reduced pitch angle of inflated plastic skins
can produce a condensation drip zone up to one metre (three feet) either
side of the gutter and up to ½ metre(39”) at the lower end of the
vent in straight rafter buildings, greatly reducing the safe growing area
(see diagram 1). The recent introduction of AF films has resulted
in even greater condensation run off from the roof skin causing more condensation
to flow to the drip zone. The drip zone provides an ideal environment
for disease entry that can impact on the whole crop, resulting in a reduced
growing area as well as additional spraying and energy consumption to dry
out and ventilate the environment to prevent crop infection.
Redpath's innovative approaches to greenhouse design
have resulted in a larger safe growing zone for the crop, reducing risk
to the grower from plant disease as well as increasing the effective growing
area giving significant returns to the grower. The combination of
the Cosecant Curved Rafter and Redpath Triple R feature provide the optimum
in greenhouse ventilation under the adverse conditions of rain and high
humidity condensation conditions (see diagram 2).
Cosecant Curved Rafter
The cosecant curved rafter has provided the additional
angle required on the lower skin of twin skin houses to allow the condensation
runoff to flow to the condensation trays at the gully. The effective
safe growing area can be increased by more than 25% with the curved rafter
design compared to the straight rafter house. In single skin structures
with the cosecant curved rafter the plastic naturally ‘tracks’ the shape
of the curve providing excellent condensation runoff.
(Note: The cosecant curved rafter has superior
crop loading capacity compared to straight rafter structures, this is particularly
important with the higher pole height used in modern buildings)
Triple-R Feature
The Redpath Raised Ridge Feature provides the
ideal ventilation for the environment. Increasing the pitch of the vents
has two major advantages firstly by allowing a wider vent opening under
rain conditions and still shed the water this is particularly suited to
the warm wet growing conditions where heat stress on the plants can be
a major problem. The rain vent position has been increased from 250mm
recommended opening to 420mm (a 68% increase). Secondly, the Triple R feature
allows the vents to be opened further under high condensation conditions
without condensation ‘run back’ to the ridge particularly in single skin
environments. The condensation purge position has increased from
150mm(6”) to 320mm(12”) (over 100% increase) reducing the disease risk
through better condensation control.
1 NZ Reg. Design No. 25666
2 Patent Pending App. No. 337731
