I'll go ahead and ask two questions first then explain in detail what I am trying to accomplish.
If I screwed together eight 10 foot sections of 1/2 " galvanized metal pipe to make an 80 foot length of pipe that would be fastened to the top of concreted 9 to 10 foot high 4x4 wood posts at either end of an 80 foot long area, would that work without sagging in the middle ?
If I spliced together enough 12 foot long 2x8 boards to make an 80 foot long ridge board that would that hold up by itself between the 2 4x4 posts ?
(I would also concrete four 4x4 posts (about 4 feet high) just outside the fence on both sides (12 feet apart) at :the midway point and have a rafter board going from the top of each post to the ridge board for added support in the middle of the 80 foot length.)
Now let me explain what I am trying to accomplish as it is not your usual home / yard DIY project, then I'll ask my specific questions.
I have an area of our yard fenced in with a 4 foot high wire fence attached to metal fence posts, it is 16 feet wide by 80 feet long, it has a gate to go in/out, and it is for our Border Collie mix dog to have plenty of room to run freely and get her exercise when I take her outside and throw Frisbees and balls.
The general problem I am trying to solve is covering the entire 16x80 area with 2 large tarps to have a canopy that would cover from the top of one side of the 4 foot fence to the top of the other side, the entire 80 foot length.
Why ? Because here in South Carolina we can go thru times where it can rain enough over a few day period to have several days in a row where our dog has no outdoor running time (and a dog can get very frustrated with pent up energy when they are used to being able to run) and having her fenced in area covered allows her to get exercise on rainy days as well as the added bonus of both my dog and I being shaded from the hot sun during the summer months.
I had it covered very nicely using 3/4" PVC pipe and connectors for an arched frame to put the tarp over (sort of like how a PVC greenhouse is made, but the pipe went from the tops of the fence posts). Then less than 2 weeks later we had a (very rare for here) very heavy snow that collapsed it.
So now I am trying to figure ways to have a sturdy frame under the PVC that would hold up under such rare weather.
I had thought of screwing together 10 foot sections of 1/2 " galvanized metal pipe to run the 80 foot length, between concreted 9 to 10 foot high 4x4 wood posts at either end,
but would that work without sagging in the middle ?
Another idea is to splice together many 2x8 12 foot boards to make an 80 foot long ridge board that would give support underneath the PVC framing.
Now I would prefer to not have any support posts inside the middle of the yard to be able to keep a completely open running area.
I would also concrete four 4x4 posts (about 4 feet high) just outside the fence on both sides (12 feet apart) at :the midway point and have a rafter board going from the top of each post to the ridge board for added support in the middle of the 80 foot length.
Would that be enough support for that long of a ridge board, or would I have to use one or two support posts in the middle of the yard (either one in the middle, or two spaced at 1/3 intervals) ?
Also, any other possible solutions are welcomed.
We are on a fairly tight budget and I am trying to mostly use treated lumber we have sitting around from a past project we opted not to do for now.
I have six 12 foot 4x4 posts, sixteen 12 foot 2x8 boards, four 12 foot 2x10 boards and some assorted hardware.
If I had to buy a few more items that would be ok, as long as it was very little added expense.
Thanks in advance for any help or other possible solutions.
As you can see, this is not your average DIY project :)