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Which wires do you tension on a trellis?

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mark g

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In a VSP trellis system you have several wires running between end posts. A bottom wire to support the horizontal replacement rods, a top wire and several moveable wires in between. I have read several presentations on trellising and they mention tensioning of wires to somewhere between 230 and 300 lb.

The problem is they do not mention which wires this load applies to. Should each and every wire between end posts be individually tensioned to 300 lb? Perhaps it's only the top and bottom wires. The more wires that are tensioned to the 230-300 lb range then the greater is the horizontal load on the endposts ie it becomes multiples of 230-300 lb. If I'm using a relatively flexible metal end post then the endpost will flex heavily unless the anchor wire is also tensioned to multiples of 230-300 lb.

Could someone please provide a bit of guidance on this tensioning busines? I know inflexible deeply sunk rail sleepers would remove this problem but metal posts is what I have and what I need to figure out how to use.

Cheers, Mark
 

balatonwine

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All wires should be under tension. Vines can have a lot of weight that needs to be supported.

Bottom wire supports the canes.

Second to bottom wire supports the grape clusters.

Remaining wires prevents the vines from sagging into the rows. And to help prevent deformation in high winds.

But.... That being said.

I managed a vineyard this year that had absolutely no tension on the wires, for reasons I won't get into here. It was really a pain on many levels, especially during winter pruning and trying to tie down the canes. But, it was not a total disaster either because it had a double wire setup (that is, wire on each side that the vine grew up and between for support -- so twice the amount of wire I use on my own single wire setup). It did take more work to trim and deal with the vines, and I had to green prune more, including more frequent hedging on the top because there was no possibility of delaying this or any "comb over" due to no wire tension. But it is "doable" (as long as you either have a lot of time, or not many vines ;) ).
 

mark g

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Thanks for the reply. Definitely helpful to know all wires should be tensioned. If I had an 8 wire VSP set-up then I could end up loading the posts with 8x300 lb force due to wire tensioning plus an additional amount for the weight of the vines plus any wind load on them. It seems like there is little info available on this subject other than loading on individual wires rather than loading on the endpost anchor. If anyone could point me to some literature it would be a big help

Many thanks

Mark
 

BigH

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I have read several presentations on trellising and they mention tensioning of wires to somewhere between 230 and 300 lb....The problem is they do not mention which wires this load applies to. Should each and every wire between end posts be individually tensioned to 300 lb?
I keep the fruiting/cordon wire under "proper" tension, but don't tension the catch wires aggressively. The first year I had everything tight and I noticed the 6" end post of my H brace moved a bit from the horizontal load on it. Have not had a problem since I reduced tension on the catch wires.

I have seen videos of vineyards that use moveable catch wires that they swing from the ground up to a latch on the post, catching shoots a pulling them upward in the process. The catch wires did not seem all that tight. Maybe they go back and tighten them, but that would take quite a bit of time in a large vineyard.

H
 

balatonwine

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Thanks for the reply. Definitely helpful to know all wires should be tensioned. If I had an 8 wire VSP set-up then I could end up loading the posts with 8x300 lb force due to wire tensioning plus an additional amount for the weight of the vines plus any wind load on them.
The tension force you are reading is best for vineyards with properly installed anchor posts, and ideal with high tensile wire (which should not stretch, and since it does not really bend well, may break by lateral stress from the vines if kept too loose). I would not worry too much about such high tension if your end posts can not sustain that, or if you are using normal wire since such wire will stretch over time, and in a few weeks it will be loose anyway. So don't over think this.

I assume your eight wire system is doubled (two wires at the same height on each side of the post, so a total of 4 wire rows). For, that as I said above, I would just try to keep the wires "snug" during the season to keep a reasonable stable and upright growth platform (re-tighten wire when and if needed) and tuck the growing shoots between the wires. You should be fine.
 
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