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Howdy
Any engineers out there?
I need to span my 60' chicken pen to hang netting or wire, to keep out hawks and owls.
I'm thinking to make trusses with 3/8" rebar. Two straight on bottom, with a single curved on top. Triangulated supports every foot, bottom pieces parallel at 6", top curve 6" at center. Hopefully I described it well enough.
Thing is, on a 60' span, is it going to hold up some netting/wire, let alone collapse from its own weight. I've calculated the weight @ 72lb per truss.
We do blueberries with poles and a galvanized steel wire. The pole tops are 9 to 10 feet at the top, and the wire - I don't remember the gauge but it's about .090" .. I can verify that if needed. The poles are about 40 foot apart. The netting is a 1/2" opening and when we were in it deep, we covered 3 1/2 acres!
It took 4 to 5 people 7 days to get it all up and tied together and secured to the wire. Then we'd pray that there wouldn't be a Nor'Easter or a hurricane.
The wire and poles makes more sence than hanging all that iron in the air. You'd have to have walls or columns to support that weight. I put up a lot of overhead cranes you don't realize the weight when you start. Poles and wire work for me.
sixty by what ?
I would not use rebar, to heavy. You can put a row of support poles down the middle every 10' and use 1/8' clothes line cable to support your 2" mesh chicken wire. Use cage clips to hook your wire to cables.
Sixty by sixty. 1" EMT, 10' sticks, every 10'. Buried 18" with concrete.
What are cage clips?
Cage clips are used to make wire cages for various animals. Click here.
You could also use those galvanized chain link ties. Most home supply stores carry them.
My preferred option would be wire too.
We ran some commercial hydroponic beds for some years, and at various times had to cover them with shade-cloth; which is quite surprisingly heavy.
Our overhead wires were 12.5 gauge high tensile wire, at spacings of (from memory,) about 8ft, and never had a failure.
To tension the wire we used these: https://www.google.co.nz/search?q=ha...Wdm4CwDA&gbv=2
The black plastics in those pics are insulators for electric fencing, which you won't need.
From the pics it appears they're being used there in vineyards or kiwifruit orchards, and using the same 12.5 wire we did.
So it appears to be a fairly universal option.
P.s. Also shown there is the handle you'll need for tensioning, as well as the chain-grab strainers for taking the initial load before putting the permanent strainers in place.
Wire is a possibility. Bird net is pretty light. My biggest concern would be that the 1" EMT is pretty flimsy. There are a couple big pine trees in the yard, and limbs will fall. If I made the wire weaker than the EMT, then it wouldn't pull the whole mess down.
I'm having another thought: bamboo. It's ridiculously light. And I can get it free.
The budget for the rebar trusses would be just south of $900. Free sounds better.
I found a good site for truss know how Trusses - Steelconstruction.info.
I've been wanting a large awning for some time now. Since I'll be cheaping out on the chickens, maybe I'll tackle the truss project to the awning!
This pole system works well for me. You can usually get 2" galv pipe at the scrap yard. I use it for 60' dog runs with military grade camo netting with nylon cord for shade. That would not be good for owls or hawks because they would get hung up on it. The 2" mesh wire would flex but not tear. I like it because we get winds here at times in excess of 60 mph.
what about PVC PROPERLY DESIGNED - - - - I've seen some nice cages done with it.
https://www.google.com/search?q=pvc+...ih=541&dpr=0.8