Trellis pole spacing

[Genacide]

I'm planning on setting 2 - 4x6 posts that are 20 foot long about 3 feet into the ground for my trellis. My question is can I set these without a guide wire to the ground, just a wire from the top of the posts to the other, and how far apart can I go before I should consider adding a post in the middle?
Many Thanks

 

[nagmay]

I have 2 - 4x6, 20' posts for my trellis. They are about 30' apart, which is enough for 8 hop plants evenly spaced. each pole is only 3' in the ground.

However, I do have guy-wires running to ground anchors on each end. This is what holds the posts into the ground and keeps them from being pushed over in a strong wind. Without the wires, I could have easily pushed the poles over by hand. With the wires this thing is a tank!

 

[GVH_Dan]

Figure each plant weighs 35 lbs with cyclic loading from wind that doubles that or more. If you have a good canopy going, it becomes a sail. guy-wires are usually required.

 

[nagmay]

Few more notes about guy-wires:

A common angle would be 45°, but I didn't have 17' on the ends to make this happen. Mine are about 8.5 out (so 67.5°). You can calculate the tension on the guy (and ground anchor) using the following formula:

• force / cos(angle) = tension

So, lets say there is a max of 1000 lbs of force due to the weight of the hops and wind gusts.

• 1000 / cos(45°) = 1414 lbs
• 1000 / cos(67.5°) = 2613 lbs

 

[Genacide]

What is the preferred way to anchor the guy wires to the ground?

 

[Genacide]

Would cementing in the poles be a good alternative to guy wires? Reason being is I don't have the room for long guy wires.

 

[nagmay]

What is the preferred way to anchor the guy wires to the ground?

I used 3/4" x 4' auger anchors, but they can be hard to get in. Others have used "duckbill" style earth anchors. Just make sure that they can hold the tension (+2600 lbs in my case).

Would cementing in the poles be a good alternative to guy wires? Reason being is I don't have the room for long guy wires.

Cement is used to make a snug fit and add a little weight. It's not going to add much support with those size poles - unless you sink them much, much further into the ground.

If it's any comfort, I asked all the same questions when setting up my first trellis. Unfortunatly, with the forces involved, you really need some guy-line support.

 

[Genacide]

Should the guy lines extend out to the sides of the main poles, in line with the main wire that runs between the poles, or perpendicular to them at 90 degrees?

 

[nagmay]

Should the guy lines extend out to the sides of the main poles, in line with the main wire that runs between the poles, or perpendicular to them at 90 degrees?

A single line needs to be directly in line with the top wire. Anything else will pull the post out of alignment.

You could, instead, have 2 wires on each end spread apart at 45 degrees. This would be super strong, but harder to implement. I was originally going to do this, but I am glad that I did not. 3 years in the ground, the single wire has been sufficient.

 

[BeerFst]

Would cementing in the poles be a good alternative to guy wires? Reason being is I don't have the room for long guy wires.

You could do something like this, http://www.solutioninn.com/images3/50-E-C-S (1850).PNG

basically put a length of tube to meet the wire part way through the 45 degree and then run it straight down from there

 

[Genacide]

Should earth anchors be put in straight down or at an angle from the post (angled toward or away)?

 

[nagmay]

Straight down.

This gets it as deep as possible.

 

[tjpfeister]

*technically* the strongest way to put your earth anchors in is in the same angle as your guywire. This can be tricky, but if you start vertical for the first few inches then keep applying pressure towards your angle as you screw the anchor in, it can be done fairly easily. Your next best option is just straight down. I only had 8 to put in, so I went angled. If I had several acres, I'd consider straight down because I'd likely have a bobcat or something to power them in with.

View attachment 1431054505772.jpg

 

[nagmay]

*technically* the strongest way to put your earth anchors in is in the same angle as your guywire.

Not according to the USDA and Forest services:

"The anchor should be installed perpendicular to the ground surface. As the angle of pull nears perpendicular to the ground, the anchor should be installed vertically. The objective is to avoid having the direction of pull in line with the direction of installation and to maximize the distance of undisturbed soil."

Via: http://www.fs.fed.us/eng/pubs/html/93241804/93241804.html#anchorinst

 

[tjpfeister]

The physics of the above link bother me. I agree that the soil in line with the anchor would be disturbed, and thus the weakest soil. However, by design, the anchor *itself* is strongest when you pull in line with it (and perpendicular to the to the greatest friction surface, like the auger on the bottom). But who am I to argue with the Federal Government?

Unfortunately, when you start googling the subject the above link keeps appearing at the top of the search and the above link is about the only one that spells out an actual angle in writing. Frustrating for forming my argument, right? The manufacturer's websites constantly show them being installed at angles parallel to the cable, but generally don't state that in writing. Perhaps this is a liability thing. Or perhaps it is a "every case is different" thing. Or perhaps every municipality is different. I know if I go outside and take a walk down my road that every power pole with a guy wire will have a parallel anchor.

That said, I'm not here to hijack this thread. My pole spacing is 36' with 11 plants in between. However, this is my first year with this trellis, so I am not able to report how well this will work, just that it is slightly wider than most published commercial layouts.

Oh, I did find one manufacturer that states "The DUCKBILL® can be driven at any angle. In guy applications the angle of the installation should closely match the angle of the guy line."
That can be found here, on page 4 (labelled as 3):
http://www.earthanchor.com/wp-content/uploads/2014/03/FOR-3213-DUCKBILL-InstallationV2.pdf