trellis backbone question

[JUST_BREW_IT]

What are you guys using as your backbone for your trellis systems? I'm looking at some vinyl covered galvanized rope wire like this. Will this do?

http://www.ebay.com/itm/Clear-Vinyl...5780201?pt=LH_DefaultDomain_0&hash=item233529 b169

 

[rgauthier20420]

This is very similar to what I've got spanning a 30' gap between 2 EMT poles in the ground. We are using a turnbuckle in between the poles and the poles are counter supported on the other end with another turnbuckle that's clamped to a piece of EMT that's been pounded into the ground. It's working very nicely.

I wouldn't use this unless you use turnbuckles for tightening.

 

[JUST_BREW_IT]

I'm going to use an old come along or hand winch for tightening when the backbone begins to sag. Do you think the rope wire I attached would hold the weight?

 

[rgauthier20420]

Hmmm the listing says it's got a break strength of 920lbs....so I think so

 

[JUST_BREW_IT]

but the working load limit is 184 lbs. I'm not sure what the difference is?

 

[rgauthier20420]

but the working load limit is 184 lbs. I'm not sure what the difference is?

I found this nice description of the 2:

There is a difference between the tensile strength of a rope and its safe working load. Tensile strength is the force required to break it, which can be determined by testing. However, in the real world of rivers and the outdoors there are factors that impact or reduce the strength of any rope. These include; tying a knot in the rope, its age, environmental deterioration (hot and cold), abrasion and rubbing on objects, harmful substances, water and sand/grit, and the rope's previous use and care. If a person is on the end of a line we obviously don't want the rope to break. To factor in the above variables we use an arbitrary number to reduce the actual load that is placed on the rope. This number is called the safe working load. The ratio between the working load and the rope's tensile strength is termed the safety margin. If a rope is rated at 5000 lbs tensile and we wanted to maintain a 10:1 safety margin, the maximum working load would be 500 lbs.

Looks like it's a safety margin. How many plants are on the line? A full grown plant can weight up to 30lbs, so that puts about 6 plants on based on the "working load". However, I'd imagine you'd be more than safe putting many more on there just based on the description above.

 

[nagmay]

I just set up a trellis using 20'poles (4' in the ground). At this height, you need to consider more than just the weight of the hops. A good gust of wind can turn the bines into a sail and put a lot of extra force on the wire.

I went with 1/4 galvanized 7x7. Twice the price, but 1400# working, 8000# breaking (listed wrong on site). This is what people use for zip lines.

I am not a structural engineer, so take the following with a grain of salt:

There are professional yards that use 3/16 between the poles and 1/4+ guy-wires from the poles to the ground at a 60deg angle. The reason you need thicker wire is that any angle away from the horizontal means greater tension. At 60deg, the tension is about twice that of the horizontal weight. With 22' above ground, you are going to need guys - or - really, really strong poles and wire.

 

[JUST_BREW_IT]

I ended up going with this stuff. What do you guys think?

http://www.ebay.com/itm/151070331453?redirect=mobile

 

[atsorrento]

Glad I came across this thread. I live in central Florida (hurricane alley) and have sandy soil. I put two 16X4x4's about 3.5ft in the ground w/a 12ftX2"X5" cross beam at the top. I was thinking of re-enforcing the vertical beams as they do telephone poles. Overkill?

 

[JUST_BREW_IT]

Glad I came across this thread. I live in central Florida (hurricane alley) and have sandy soil. I put two 16X4x4's about 3.5ft in the ground w/a 12ftX2"X5" cross beam at the top. I was thinking of re-enforcing the vertical beams as they do telephone poles. Overkill?

I honestly don't think utility poles are going to be overkill. You can get different diameter poles and I think the smaller diameter poles will do just fine and can be had for cheap at your local power company in the way of old, used poles. I think I am going to get my utility poles for 10 bucks per pole. In my area 16 foot 4x4 are roughly $22 so there is a significant savings there AND you will be able to get much higher.

My brother inlaw is a carpenter (very good one at that) and he told me to stay away from 4x4 in such an application where the majority of the poles will be stand alone above ground. He said that the poles will warp horribly in the summer sun and look awful. He said that 6x6's would not warp. There again, 6x6's are pretty darn expensive in comparison to the utility poles I'm eyeing. I think a guy would paint or possibly stain old utility poles where the majority of the creosote has worn off and have them look pretty good............ I'm going to find out

 

[JUST_BREW_IT]

Glad I came across this thread. I live in central Florida (hurricane alley) and have sandy soil. I put two 16X4x4's about 3.5ft in the ground w/a 12ftX2"X5" cross beam at the top. I was thinking of re-enforcing the vertical beams as they do telephone poles. Overkill?

Ah, I misread. You're talking about reinforcing with guy wires. Search the site. Many on here do just that.

 

[atsorrento]

Good point about the 'old' utility poles. As they say, one man's trash is another man's treasure


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