| |
|
How
to assemble:
A windbreak
Windbreaks:
Why
install windbreaks?
There
are a number of advantages to be gained from the assembling of windbreaks.
- Prevents
physical damage to plants such as wind scarring, broken branches and
fruit and blossom losses
- Slows
evaporation which means more efficient use of water
- Windbreaks
raises soil temperature which helps crops ripen earlier
- It
prevents soil erosion
- It
also prevents the spread of soil and wind-borne diseases
- Windbreaks
assist pollination and increases the efficiency of micro-sprays and
other forms of irrigation.
- In
some cases, a windbreak can help retain humidity levels enough to prevent
overnight frost.
In
contrast to natural windbreaks, Alnet windbreaks are quickly erected,
save potentially productive land and do not compete with your crops
for plant foods and fertilizers. Alnet windbreaks do not harbor harmful
insects and bacteria. They can also be erected in any configuration which
least inconveniences the use and passage of tractors and implements.
How to assemble a windbreak:
Position:
The best results are achieved when a windbreak is positioned as near as
possible to a 90-degree angle to the prevailing wind direction. Roughly
speaking, a windbreak thus positioned will protect a horizontal area 10-15
times the height of the windbreak.
Remember:
Extend the ends of the windbreak by a few extra meters on both sides to
allow for faster airflow, or "spill-round", which occurs at
the ends.
Bracing:
Many variables such as:
- topography
- wind
direction
- nature
of the soil
- height
of the windbreak
- and
working space required
will
influence the choice of your bracing system. The structural stability
of the windbreak is only as good as the bracing used and the higher the
windbreak, the more critical the strength of the bracing. No matter how
well they are planted, the poles alone are inadequate to control the considerable
force of an average wind.
Spacing
of poles:
As a general rule, the maximum surface area of material between poles
should not exceed 196.85 ft² (60m²) for 40% shadecloth and 147.63
ft² (45m²) for 55% shadecloth.
In
very windy areas, or anywhere where a height of 19.68 ft (6m) is to be
exceeded, the space between poles should be decreased accordingly. It
is worth remembering that lower windbreaks are easier to erect and maintain,
and are thus more practical despite the closer spacing required between
breaks.
Anchors
and struts:
The accompanying illustrations show some of the more commonly used types
of anchors and struts.
Assembly of the windbreak:
Note:
The example which follows is based on a windbreak 164.04 ft (50m) in length
and 9.84 ft (3m) in height. The same basic method will apply equally for
higher structures.
| (a)
|
Before
planting the poles, drill holes and cut notches to accept the braces.
If the poles are particularly rough, or have been treated with Creosote,
cover the sides of the poles which will come into contact with the
shade netting with narrow strips of old PVC water piping. This will
minimize chafing or adverse chemical reactions. |
| (b) |
Now
plant the poles and brace them securely. |
| (c) |
The
windbreak material has rows of eyelets along its length.
Five
lengths of high-tensile steel wire are threaded through the eyelets,
using only one of the two center rows. In order to leave a piece
of material free for attaching to the first and last poles, start
threading only at the fifth eyelet, ending at the fifth eyelet from
the end.
When
all 5 wires have been threaded, tie wire 'A' to the top (9.84 ft
(3m)) of the first pole and pass the other end of this wire through
a heavy staple at the top of the last pole.
|
| (d)
|
Now
tension wire 'A', causing the material to lift and hang like a curtain. |
| (e) |
Gather
and tie the material loosely at the first pole to prevent it sliding
along the wire. Measure 9.84 ft (3m) down from wire 'A', and fix wire
'E' to the first pole, after which you can also fix wires 'B', 'C'
and 'D' to the pole. |
| (f) |
Now
fold the loose flap of unthreaded material a few times and nail
it to the pole from top to bottom using old PVC water piping and
large head nails. If using steel poles, wrap it around the pole,
fold the end double and sew it back onto itself.
|
| (g)
|
Move
your ladder to the top of the second pole and slide the material along
wire 'A' until the top edge is taut. |
| (h) |
Position
the wire at 9.84 ft (3m) above ground level, and staple the wire and
material to the pole. Working over the top of the pole from the back
for greatest comfort, repeat the process, pole by, taking up any slack
which develops. |
| (i)
|
Having
completely fixed wire 'A', pass wire 'E' through a heavy staple nailed
9.84 ft (3m) below wire 'A' on the last pole and tension but do not
fix it. Wire 'E' will tend to bow upwards as shown in the illustration.
|
| (j) |
Move
to the second pole and pull the material taut whilst pulling wire
'E' down to its position 9.84 ft (3m) below wire 'A'. Now staple wire
'E' and the material to the pole, and repeat the process, pole by
pole, taking up the slack which develops each time the bow is pulled
down. |
| (k) |
Now
tension and staple wires 'B', 'C' and 'D' to each pole in turn.
|
| (l) |
Finally,
fold the loose flap of unthreaded material at the end of the roll
around the last pole and either nail or sew it, as described earlier
and depending whether wooden or steel poles are being used. |
The
basic windbreak is now complete except that, if the design calls for bracing
on the side to which the material is attached, this must now be done.
Stabilizing the billowing effect:
To
prevent the material billowing back and forth in the wind - which eventually
causes the threaded wires to break at the points where they are fixed
to the poles - additional wires are tensioned parallel to wires 'B', 'C'
and 'D', but on the opposite side of the poles.
The
poles thus act as spacers between the two parallel sets of wires and this
space can be increased by nailing wooden blocks onto the poles.
Now
roughly divide the distance between the poles into three, and bind the
parallel wires together at these points. This stabilizes the billowing
effect.
Other
building projects:
|
|
