Z47 Vineyard Posts

Benefits of a STEEL Z 47 trellis system for your vineyard

Wood vs. Steel Traditional vs. New

Why look to steel in your new vineyard?
A steel post offers many benefits to grape growers and has been successfully used in New Zealand vineyards for many years.
But the BIG question mark with steel is STRENGTH?

Are they strong enough to handle canopy loadings of 15 to 20 kg/m?
Are they strong enough to handle high wind loadings under full canopy?

Good Questions.

The Good News
Steel is a strong and versatile material and can be rolled or formed to any shape. Comes in many grades of strength and thickness and can be protected for long life.
These features allow for great movement in design

The Answer
A post designed for use as a grape trellis post, strength plus flexibility, easy on wires….

We've called it the Z-47

Steel offers Benefits like:

  1. Ease of installation and use compared to wood posts
  2. Ready to use once they are driven into the ground, just string your wires up
  3. Increased versatility (lots of built in options for EASY wire placement)
  4. No need for plastic clips, staples nails etc….
  5. More efficient harvesting with mechanical harvesters (more fruit harvested with less beater power of harvesters)
  6. More consistent QUALITY than wooden posts
  7. Environment friendly- and can be easily recycled after its useful life.

If you follow the guidelines outlined here, we know you will enjoy the many benefits of the new revolutionary steel Z-47 post for many years to come.

Strength-Pull Test

High strength galvanised steel.
The Z-47 is made from HIGH strength (G500) Hot dipped (Z450) galvanised coil steel. This zinc coating is almost twice that of a galvanised steel roof.
The Z-47 is available in 1.6mm thick coil and 1.9mm thick coil.

Z47 Vineyard Posts
Close up of the unique Z section.

Superior Strength- the Z 47 and the Z 47 S
The Z-47 is the only post (that we know of) that is Z in section. This unique shape offers great strength under heavy loads and excessive wind loads.

Because the weakest point of any post is at ground level, we have designed this point for MAXIMUM strength.
The addition of a sleeve crimped to the Z 47 post at this point has resulted in a post that is unbreakable at ground level.
That's right, a post with its weakest point now it's STRONGEST.

WE have called this post the Z 47 S

Pull Test Results

Posts were 1.9mm thick x 2.4m long
Pulled at 1.2m above the ground with 0.6m of post in firm soil over clay
Z 47
Z 47 S
No. of kg
Deflection (mm)
No. of kg
Deflection (mm)

The Z47 about to be tested
The Z 47 SL under load at 185 kg.
Note the ground movement Post after test.


Motorway Median Barrier
We don't recommend you stop and take a look but the wire ropes used on the motorway median barrier are supported by a post that is Z in section

Post flexing under load

Flexibility with Strength
Why design a flexible post? Why not a solid post?
A solid or rigid post is not able to absorb high energy. (Have you seen harvesters break wooden posts)
If a rigid post is not of sufficient diameter it will not remain secure.
They may have gaps at ground level and “wobble “a bit. A flexible post absorbs energy better; be it from harvesters or wind.

It is important that a flexible post has good in ground stability to absorb this energy and remain firm in the ground without “wobble”.

Superior In ground stability

At 55mm wide the Z 47 S offers a wide face for resistance to ground movement.
Its open shape offers a LARGE surface area for soil to grip the post.

Z 47 S posts are FIRMLY held in soil

For normal ranges of productivity in reasonable strength soil as well as drained loams over light clay there will be no noticeable settlement.

The standard embedment depth into firm ground is 600mm. This allows for a top layer of 100mm of loose organic loam

Fixing of Wires

The REVOLUTIONARY Wire Friendly Retention Tongues

Revolutionary Wire Friendly Retention Tongues

Other steel posts are very abrasive on wire, or they come with a plastic clip that needs to be attached.
Well we've designed a tongue that cares for your wire

No Abrasive edges.
No wire damage caused by wind movement.

The new wire friendly tongues unique profile is designed to CARE for your wires.
The tongues are curved to allow the wire to SLIDE.
The tongues are able to accommodate up or down loads in undulating land.

Because the wire is held snugly in a V formed tongue there is no wind chatter
For good retention the wires are twisted slightly to enter tongues.
The BEST for wire security

(Because some may want the plastic wire care clip; we have provided a built in option,-a hole at each tongue to accept a plastic clip fastener.
But try the tongues FIRST)


Benefits of steel Strength- Pull Test Flexibility Fixing of Wires Installation Long Life

Recommend MAXIMUM post spacing

There are three broad categories of situation:

  1. Perimeter Rows
  2. End 10m of any row
  3. Internal Rows

The spacing are based on typical rural levels of wind exposure.
In addition there are situations where the wind is accelerated for local reasons such as (in order of increasing severity)

Particularly bare surrounding paddocks
Small scale funnels caused by gaps between nearby trees or buildings
Large scale funnels caused by valleys or the lees of hills
Ridges and escarpments.

The table below gives post spacing for the main grape growing regions and the three situations identified.
In most locations the strongest storms come from an identifiable quarter. (often the West)
Perimeter rows and end of rows with high wind exposure should have Z 47 S posts at the recommended spacing
This spacing should extend to the 2 rows inside that.

Recommended Maximum Post Spacing
Zoning Note (1)
Post Usage (spacing in meters)
Perimeter Rows
Note (2)
End 10m of any Row
Note (3)
Internal Row
Note (4)
I: Exposed sloping ground
II: Within 500m from the sea or large lake
III: All other vine growing areas

Wind Zone I is equivilalent to lee or exposed zone of NZS 3604
Wind Zone II is equivilalent to open terrain of NZS 3604
Wind Zone III is equivilalent to rural terrain of NZS 360

(2) Perimeter row is that on the exposed outside of a interior row.
(3) This is the exposed end of 10m of all rows.
(4) This is the internal row inside the perimeter and ends.

Wind Loadings

The 10 year return period winds for the main grape growing areas in New Zealand are as follows:

Kumeu 34 m/sec
Gisborne 30m/sec
Hastings 32m/sec
Martinborough 39m/sec
Blenheim 32m/sec
Canterbury 34m/sec

This means that for example with the 34m/sec, a 120kph wind measured at 10m above ground level is likely to occur once every 10 years if the block is equally exposed from all quarters.
If the vineyard is sheltered from one quarter the probability of a trellis-damaging wind is reduced according.

Driving posts into ground
Posts are best installed using a percussion driver or a hydraulic ram pushing the post down.
Ideally the post should be guided in a tube with the hydraulic ram pushing the post through.
Posts can be installed by hand using a hand driver.( But driving these posts by hand are hard yakka)
In gravel or stony ground (when stones are greater than 50mm) pilot holes should be pre-formed either by ripping the ground or spiking (solid rod or crowbar).

We recommend 600mm in the ground.

Long Life

Long life expectancy

Life expectancy of steel is determined by the environment and corrosion resistant coatings that are applied
The durability of the Z 47 post is very dependant upon the soil type (acidity/Ph level) and drainage.

Above 300mm from ground the Z 47 post will exceed normal usage life of the post.
Above ground to 300mm above ground the rate of corrosion is determined by the corrosion at the ground level.
The corrosion behaviour of buried galvanised steel varies greatly with the type of soil.
Knowledge of local conditions is therefore essential in estimating the life of galvanized steel posts with best life performance in alkaline and oxidising soils.
Fortunately soil conditions in vineyards are generally conducive to giving steel long life.

Galvanizing is well recognized for its protection of steel but did you know that LANOLIN has been used as a natural corrosion inhibitor on steel for over 50 years.
YES, LANOLIN, the greasy substance in wool.
It does a great job of protecting steel.
Accelerated laboratory tests show lanolin rubbed in over galvanized steel greatly INCREASES the life of steel.
We are able to offer this added protection.

Sheep never get wet
The lanolin on the wool absorbs moisture. It is the greasy substance on the wool that PROTECTS the fibres from the environment Fine wool breeds, such as merino, yield the most grease.

The Z-47 is made from a wide (mother) coil, slit to 122mm wide, then rolled and punched (tongues formed).
Because the tongues are formed after the galvanizing process the cuts have no zinc to protect them .
Fortunately the sacrificial nature of a zinc coating ensures that no more than a slight discolouration will blemish the appearance.

Corrugated Iron
Have you ever seen corrugated iron roof rust from the cut end? Or rust formed across the end of a cut wire.
The sacrificial nature of zinc means it will self heal any small cuts or surface Scratches

Deal Direct with the factory
Because the posts are made right here in South Auckland (not far from Glenbrook Steel Mill) you can enjoy all the benefits of a 100% New Zealand made post

Benefits like:

  1. Posts made to ANY length
  2. Tongue positions to suit your trellis configuration
  3. Accommodating your frost protection sprinklers
  4. Competitive freight costs to your vineyard