Wednesday, April 5, 2017

High tensile fence, 5 years experience

There is nothing that a cow finds more delicious than young fruit trees, and they'll destroy them if they get the chance.  So I'm putting a good fence around my new orchard to protect it. 

I've been using high-tensile fences as my go-to fence for the last 5 years.  When I first started I made 8 or 10 wire fences; right now my current standard is 4 wire fences, and I find that works well to keep the pigs and cows where they should be, and also works with dogs, which was a bonus for my airedale pack.

When I started using high tensile fences I used 4x4 posts for the braces.   Even pressure treated they don't hold up very well to cattle and pigs; a cow won't break your high tensile fence running into it, but may very well snap the post and lay the fence down in that area enough so that they can get out.  So I switched for a while to 6x6 posts for the braces, and then downgraded to 4x6 braces for cost reasons.  My current braces are constructed of 4x6 posts, and the field posts are also 4x6 to make them more resistant to snapping if they get heavy contact from livestock or a careless tractor operator.
H brace details.  Black is wood, green is wire
 High tensile is not meant for short distances - it's great for long runs, but at the end of every run there needs to be a brace, and most of the time it's a double H brace.  The picture above shows a double-h brace (top) and a wire-reinforced double H brace, bottom.  The wire helps support the H brace against pulls to the left and right, and if you're going to have a good tight fence you need this sort of really sturdy H brace to make it go. 

In my area 4x6 timbers are $18 each, so the brace itself costs $90 for the wood.  I use (3) 80lb sacks of concrete at the base of each post at $4 each, adding another $36.  Each individual line will need a spring and a tensioner, that run about $8 each, so for my four wire setup you're going to add another $32.  the ceramic insulators that I  use are a couple of bucks (more on these later).

I mention that because its' basically $126 in material costs for each end of your run, plus $32 for the hardware between it.  The wire itself is about 3 cents a foot.  For long runs I put a double H brace every 500 feet, or on either side of a gate opening wherever they are.

So the cost of a high tensile fence 4 strands and 50' long would be (126 + 126 + 32 + 50*4*.03) for the ends, and $18 for each of the two field posts, for a total of  $326 - or $6.50/foot

The cost of a high tensile fence 4 strands and 500' long would be $632 or $1.20/foot. (the brace costs + 16 4x6 field posts)

The longer the run the better the economics are. 

I'm describing a really hefty brace for a reason; I've pulled braces out that were set on driven-posts, were constructed of too light a timber, or just weren't beefy enough and I squished them as I tensioned the fence.  If you want a good fence you make a good brace. 


My final brace design.  Red are electric wires, black are inert
 The picture above shows an end-of-run fence brace.  I electrify the top and bottom wire of the brace.  The wires are spaced 1' apart, starting 1' off the ground.  I have tried wires lower than 1' and it's just too much of a nuisance with weeds and other stuff contacting the lower wire.  12" seems to be low enough to deter pigs, but high enough to reduce fence shorts. 

The top wire is 48" above the ground level, and is the primary wire that keeps the cows in. 

The two wires in the middle are just there to prevent animals from ducking  under the top wire, or jumping over the bottom wire.  I will place field posts so that I can direct the wire up or down to follow the ground contour, and I'll smooth the ground so that there's no depressions under the fence.  

I used to run my hot wires across the H brace but I had problems both insulating the hot wires from contact with the brace reinforcing wires (green in the pictures above) and with the posts.  there are various plastic tubes you can use, but I've never been happy with any of them.  I've switched to ceramic insulators and they do the job nicely. 
Ceramic insulator that is considering flipping (bad)

ceramic insulator being good

post ceramic insulator

Note position of ceramic insulator outside of brace area. 
 I put my tensioners in the brace area.  With the ceramic insulators placed, I can then tighten the fence without having to turn the fence off, and I have a cleaner electric fence line - so I can go longer distances and deliver a better shock.  The less contact the live wires have the more range you get out of your fence charger. 

So I'll make a brace at one end, and t hen the other, and then I'll run a neutral (non-electric wire) between the two.  I'll tension that wire, and that gives me a line to place my field posts.  I've settled on 30 to 40 feet between fence posts, and found that for a pretty fence an even spacing is all that you need.


1 comment:

Nick Keenan said...

Thanks Bruce, I like seeing the different ways people do things. If you have the insulator even with the front brace post, how do you keep animals off the fence between the back brace post and the front post? Do you just rely on the strength of the brace and the crossbeam and diagonal wire? I think pigs would be through there in a heartbeat.

As you note, for high-tensile the longer the run the better the economics. I've been using 1/4" electric rope a lot lately for short runs. It's easier to work with and doesn't have to be as tight as high-tensile, which means the bracing doesn't have to be as stout. It's good for semi-permanent spots because it's easier to take up.