This plot is in a community garden and I initially wanted a trellis that could be pulled up if needed. I also wanted something lightweight that I could install myself. If I recall, our club president at the time, Kevin, came up with this design and it's still standing almost four years later with only a couple of modifications.
We were constrained by materials that are available at our local hardware stores, so we decided on 10-foot trellises. This works out fine because the tallest ladder I can carry in my truck allows me to reach 10 or 11 feet in the air.
As it turns out, the coir twine I buy to string up the hops is just the right length to toss over the 10-foot wire. The relatively short height of the trellis may impact our yield, but for now we're focusing on good management practices instead. Besides, it doesn't do us any good to have hops reaching up to the sky if we have no way to harvest them.
This trellis is in no way heavy duty. There are nine plants that grow up it and it doesn't need to carry a heavy load. If you're looking for designs that require winches and telephone poles, click back to Google and on to the next site.
We used the fenceposts instead of securing the cable guy-wire style in the ground because of the size restriction of our garden. It would be a safety hazard (tripping and garroting) to angle the cable in the ground. The neighbors' fenceposts are cemented in the ground and are very secure.
The main drawback of this system is the cost. The green fenceposts we used were pretty heavy-duty and cost $15 each ($60). The PVC pipes were $7.40 each ($30) and the 1/8-inch cable was $18. All the other bits and pieces added about $10. Our wood trellises ended up being cheaper, even with using a bag of cement in each hole.
I was able to get all the materials at Kendall's Hardware in Clarksville, Maryland. I didn't go to a big-box store because Kendall's had the sturdy T-posts and they have an excellent selection of hardware (eyebolts, etc.).
This is a good system if you only have a few plants, you don't want to dig holes, you need to install it yourself, or you don't want a permanent trellis. As I said above, four years out, this is holding up pretty well and I think it's a pretty elegant design.