Sunday, July 14, 2013

High tensile fencing


So in keeping animals there's something that will wake me from a deep sleep with chills.  It usually starts with a phone call, but it doesn't end there. 
 
"Hello?"
 
"Hi Bruce.  This is Cora, your neighbor.  Your cows are out!"
 
"Uh, thanks.  I'll go get them"
 
You can substitute pigs or sheep for cows, and it has the same effect.  Having a good fence allows me to sleep at night, and a good perimeter fence takes part of the panic when an animal gets out of its pen.   A good fence is right at the top of the list of things I do when I've bought a new piece of land or a new farm. 
 
The new farm is the largest area I've ever thought about fencing, and because of the sheer number of feet of fencing required, I've had to sit down and pencil out fencing costs.
 
  Don't get me wrong here:  I'm not interested in a cheap fence, or an easy to construct fence, I'm interested in a fence that will be serviceable for 10 to 20 years, is relatively easy to maintain, and has the lowest cost for the function that I'd like to put it to, in about that order. 
 
The traditional fence for large acreage is a barbed wire fence.  There is a barbed wire fence around parts of this property, but it's in poor condition and it's not much more work to just replace than it is to repair.  It's also sized for cattle, which means that it doesn't work for pigs or sheep, and it doesn't do anything to exclude predators. 
 
High-tensile fencing is a very strong wire that is stretched tightly between braces.  Between the braces there is a field pole every 30 to 100 feet, and you can either use the fence with or without electricity.  I'm constructing an 8 strand fence with alternating strands of grounded wire and electric wire. 
 
 This is the story pole for this fencing project.  It marks the locations of the wire and which strands are electric and which are not, and is designed to be used from the top of the brace poles.  I've nailed a scrap of wood to the top so that you just hang it from the brace while you transfer the markings to the poles. 
 Each of the 8 strands of fencing are tensioned to 250lbs, which means that we need a strong brace to hold up against the 2,000 pound static pull that the fence will put on this brace, and the brace needs to be strong enough to withstand the force if an animal runs into the fencing full-tilt.  Each wire has a breaking strength of about 1600 pounds, and with 8 of them in play, that's a potential force of  12,800lbs.  So for the braces I've chosen pressure treated 6x6 posts.  They're buried 3 feet into the ground.  Some are tamped in, some are cemented in, depending on how firm the ground is.  Each brace is braced diagonally with wire - a single diagonal brace if the force is from one direction only, an X brace if the pull is from two directions. The brace wire is notched into the post with a chainsaw so that it doesn't slip.   People claim you need one of these braces for every 400 to 650' of fence run.  This particular brace is at the end of a 435' run. 

 This wire is particularly prone to breaking if it has even a single kink in it.  I purchased the jenny kit to unspool it, and then built the sawhorse to hold it up while we unspooled it.   The cheap simple sawhorse has been super useful over the years.  

 Each strand is tied to the post at the far end, and then tensioned from this end.  The tension ratchets come in two flavors; I chose this one that's $0.50 more expensive because it comes with a square lug on it that allows me to use standard tools to tighten it.  The cheaper one required me to buy a special handle, which I always loose. I don't need any more special tools; well worth the $4 more per brace ($0.50 more for 8 ratchets)  for the better ratchet.   
Each strand also gets a spring.  This allows the line to flex in case of impact, and also allows you to measure the strain on each strand as you tension it.  You measure the length of the coil with a tape measure.  It starts out 9" long, and is 7.5" long when the fence is under 250lbs of tension.  I used that big crescent wrench to tighten it as it fit over the square drive sprocket easily, and gave me enough lever-arm to make the tightening easy. 
 The fence stables are there to guide the wire; you want it to be able to move back and forth, and you also don't want to nick or otherwise damage the wire, creating a weak spot. 

 This particular run goes from the brace at right to the telephone pole you see in the distance in the photo above. 
 Here's the finished product.  The top wire is a ground, and is grounded with grounding stakes at either end of this fence run, for lightning protection. The electrified strands are equipped with insulators, and the whole thing is super tight.    The barbed wire fence that I'm replacing is in the foreground on the left in the picture above.  I'm moving the fence 3' so that there's clearance around the electrical utility poles.  I don't want the line crew to damage my fence if they need to do maintenance on the poles at some point in the future.  The original fence was stapled to the utility poles.  Bad practice. 

I mounted the spring and tensioners at the house-end of the strands so that it would be easy to see and adjust the strands with a short walk.  if one is broken or loose the adjustment point is close in and can be fixed with a couple of minutes of work.   For other runs I'll have to walk to them, but I've been working on having all of the adjustment areas as close to each other as I can. 

The electrical part will join this fence via a trench from the house.  I'll use some 1" water line scrap that I have from the water project as a protective pipe for the electrical line.  Inside that protective pipe will go the insulated hot fence wire.  Burying the supply lines means that there's nothing to get caught if you bring something tall through the gate, and that you can locate your fence chargers someplace easy to get to and maintain instead of on random fence posts. 

  It'll go underground near the house, travel underground to the fence post and then be attached.  I'm not sure whether I'll equip each fence run with a cut-off device.  On the one hand it's nice to be able to turn on or off fencing for a given section, but on the other hand it's something that can either break or be left off, or have an animal or person disable.  Given that the high-tensile fence is still a viable fence even with power off, I'll probably just set it up so that each charger charges a particularly area and I'll turn it on or off from the house. 

7 comments:

Rich said...

Most of my perimeter fences are barb wire with a single offset high-tensile wire so I can drop an interior electric fence almost anywhere on the farm.

I found some insulated ratchet strainers at the local feed store from Gallagher that I really like (the description says you need a tool, but I just use a wrench or pliers to tightnen it up).

http://www.gallagherusa.com/electric-fencing/permanent.component.aspx?mktprodid=1387

With the insulated strainer, it's a lot quicker, easier, and a little cheaper to put up a fence.

Of course with just a single wire, I don't worry about using the tensioning springs and let the springiness of the wire act as my tensioner (I've got 1/2 mile runs that seem to stay tight enough).

They also sell some double insulated high tensile wire that's designed to be buried. I run it under gates, etc. so I always keep the fence energized when I open a gate. The insulation is some tough stuff and I don't have to worry about getting a short in the buried parts of my fence.

Bruce King said...

Those insulated ratchets are a nice find; they didn't have any at my local supply place.

Using a high-tensile for long-span electric fence support is a great idea. That's part of the reason that I chose to electrify the perimeter fence -- you can use temporary fences attached to this one for rotational grazing.

I don't have any runs that are 1/2 mile -- the manufacturer suggested a double H brace (as pictured) every 400 to 600 feet. The springs increase the cost of the brace assembly by about $30, but I like being able to see that the lines are tight enough.

My runs are a bit shorter too because I put gates in at the corners and around areas where I might have access issues. I've had the experience of having an animal go through a hole and then having to herd them 1/2 mile back to the nearest gate, and so I usually drop a man gate or equipment gate every 1000' or so just on general principal, particularly on corners or areas that adjoin roads. makes it easier to get stuff in and out, too.

I'm going to tear down the old barbed wire fence when I'm done; I don't want to take the chance that an animal will get stuck between the two fence lines and panic. the high tensile electric should be plenty of fence.

Lee Johnson said...

I prefer high tensile smooth wire to the other fence types we've worked with. It's rare to see it in our area, let alone installed as well as yours.

I've read that beyond 500' feet you don't need the springs to provide adequate tension, but they help keep the lines tight when the weather gets hot. Some of our high tensile woven wire can get a little saggy looking when it's 90* out.

If you haven't already, you might compare prices at Premier1Supplies. They have pretty much everything related to high tensile and they were cheaper than our local farm store even with shipping.

George said...

Premier and Kencove are pretty must my favorite fencing companies.

Looks like a good job installing that fence. I'd go with some cutoffs however. It is nice to have when you're using a lot of cross fencing or want to shut down certain pastures not in use etc, to keep your kV up. I've yet to have one just up and break in years....

Mike English said...

Question from a high tensile novice. I notice you attached directly to wooden posts using the staple to hold it in place. Does the electric not go to ground through the post in damp or wet weather?

We have used both barbed wire and regular electric and if I can help it when we build our new pastures they will be high tensile!

Unknown said...

Could you comment on why your using 8 wires? Around here (in northern MN) people generally use 4 wires for cattle, and I think the most I've seen is 5 for folks with sheep.

I enjoy your blog, keep it up!

Paul said...

In addition to the above question about 8 vs 4 or 5 strands of wire. Did you figure up what the fence ended up costing you per foot?