Tarps vs. Shade cloth for flat roof structure

[FIGJAM]

Look at the flags.

Tarp angled into the wind.

No problems.

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[Strata]

Lots of great advice here. I'll echo the "build it first off playa" advice, and measuring your tarps. American or Chinese, they seem to treat the published size as a guideline. As long as it's at least that size, what's 2 or 3 inches? A real pain is what, if you've built yr shade frame to that size!

I have a 3 inch hole in about the middle of my 12x12 tarp, courtesy of a rodent in the storage shed. I edged it with gorilla tape. In last year's crazy winds, I think it actually helped to have it there. Not suggesting you poke a hole in your tarp, just a data point from a fellow flat roofer.

I'm intrigued about side walls. I might use vertical walls of 60% shade cloth that I happen to have around. Will have to see what the wind loading is like this year.

[fresh]

Reading through the thread has now got me second guessing. This will be the first year that I am building a 20x20 1" emt flat roof canopy using a 20 x 20 heavy duty tarp. I am planning on using foot pads with 14" lag screws (pondering between 1 or 2 per foot pad) and then guying down (pondering straps) into chain/lag screw at 8 points. Then have my van as a wind block on one side (it is about 20' long) with aluminet (14 x 14) going over van to shade it. Then the have one side walled off using shade cloth. The next side would have a half wall 10' with other side open, then was going to erect my usual monkey hut (12 x 18) on the fourth side. Recipe for disaster? Engineering marvel? I thought it was a good setup, but would love input. Here is my rough sketchup. Keep in mind the canopy roof would be lower, I was looking at 8' which would be less than a foot taller than monkey hut. Also not shown is the half wall, cover on monkey hut.etc... [img]

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[Roundabout]

I lost track in your description, but it sounded like your walls are all shade cloth, so I don't see any wind pressure issues. You are going overkill with the extra lags in the feet. A lag in a foot only serves to keep the leg from walking in the wind, which is a useful function, but if the air pressure builds under your roof tarp, the legs will simply lift out of the feet and off it goes. Extra lags in the feet have zero effect. The key is to cinch or guy the connector at the top of leg to the ground.

[Soliton]

FWIW,-- I used two lag bolts on each foot pad. The reason wasn't to make sure it wouldn't come loose (no chance of that!), but it allowed me to tie the hold-down ropes at ground level and kept the post base from moving (pivoting) around the single lag bolt. I used rope tied to a chain link that went up and over the top tube fitting (extra wrap there) and then down to the second lag-bolt link with a trucker's hitch. That way it was easy to adjust tension on the rope and tie knots at ground level instead of on a ladder. The extra work of putting in and taking out a lag bolt per foot was really inconsequential relative to the whole structure.

[fresh]

I lost track in your description, but it sounded like your walls are all shade cloth, so I don't see any wind pressure issues. You are going overkill with the extra lags in the feet. A lag in a foot only serves to keep the leg from walking in the wind, which is a useful function, but if the air pressure builds under your roof tarp, the legs will simply lift out of the feet and off it goes. Extra lags in the feet have zero effect. The key is to cinch or guy the connector at the top of leg to the ground.

Thanks Roundabout, Yes I am lost myself. What you say makes sense about holding from the top down. I just ordered a roll of mule tape which I hopes does the trick... which I am intrigued by Soliton. Do you have a pic of your set? So the rope ties off on a chain link ofor the lag in the foot plate and to another lag/chain? Is that then three lags at each POLE? Two in the plate, one in the playa?

FWIW,-- I used two lag bolts on each foot pad. The reason wasn't to make sure it wouldn't come loose (no chance of that!), but it allowed me to tie the hold-down ropes at ground level and kept the post base from moving (pivoting) around the single lag bolt. I used rope tied to a chain link that went up and over the top tube fitting (extra wrap there) and then down to the second lag-bolt link with a trucker's hitch. That way it was easy to adjust tension on the rope and tie knots at ground level instead of on a ladder. The extra work of putting in and taking out a lag bolt per foot was really inconsequential relative to the whole structure.

[Soliton]

Hi fresh,

Only one picture that shows this ~ only two lags per footing, each with a chain link. You could use only a single lag with an extra link, but ...well overkill is sometimes my style

pole detail.jpg

[Rusty Needles]

Hey Guys..

Such great info here.

I have a couple of questions for you non birgins:

1. We are duplicating this structure with the 2ft rebar pounded in 18" and then use the bolt welded into the bottom of the EMT to secure each leg to the playa. Will that be enough to hold our 20x20 structure? Or do we need to add guy lines too?



2. Lots of talk of crappy covers. Anyone have a link to amazon for the 20x20 that truly is heavy duty? I see a lot of bad reviews saying it's not truly heavy duty.


Thanks so much!!!

[Canoe]

... We are duplicating this structure...

Which "this" structure?

For a 20x20, you're sure leaving this late...

They're straight forward to do, and many variations, but the success lies in the details. At this late date, will you recognize all the required details, or will your structure blow way into other camps doing damage.

[Rusty Needles]

lol... I forgot to attach the link

http://wpstore.formandreform.com/blackrock-hardware-3/

We are having some bolts welded into the bottom couple inches of the EMT pipe so we can screw in an eye bolt to lock onto the rebar that will be hammered 18" into the playa.

Will that suffice for support? Or will we need guy wires too?

[Rusty Needles]

And secondly... what is the ideal height?

7 foot 3 inches makes it easy to reach top bar for lights etc. But might trap more heat by our heads?

10 ft is default pole lenth. More breeze coming thru, need a ladder for fixes.

Any input on ideal height?

Thanks so much

[Canoe]

Will it be enough? Do you need guylines?
Don't know; what will the winds be like this year and where will the air channel around your camp.

If you look at the various similar structures installed on the playa, there are usually guylines of some sort. Like the one in the photo at the top on the link you provided.
Others will guyline the connector on the top down to the playa somehow. Like a plate that is lag-screwed into the playa. Look at the photo above.
While many install a single guyline at each corner, the golden treatment is to have two guylines at each corner. More stable if there's a blow where they're needed.
The devil is in the details. Did you notice all the eye bolts on the connectors?
I read your 'some bolts welded into the bottom couple inches of the EMT pipe so we can screw in an eye bolt to lock onto the rebar that will be hammered 18" into the playa.', but there are a few ways to interpret that.

You've left this way too late.

Without getting everything pre-made to a proven design, you're going to have to take on that responsibility. You're going to have to do some reading to ensure that you have identified all of the material and construction details that matter in the variation that you're building. It's really too close to BRC opening to have time to fumble through posting this detail and that detail and finding out which you got right. Most of those with these types of structures are already on their way or on the playa building their camps.

[Rusty Needles]

Thanks for the info. We're just doing the best we can with the time we have. Well test build it all here, and plan for extra guy wires.

Any idea what would be a preferred height to build to?

[FIGJAM]

Most are 8', and say yes to guylines!!!

[gcby30]

I'm doing the same thing, virgin and giving it all a good whack by reading the many helpful replies here. I'm going with 8ft height because it will give me over a foot of clearance between top shade cloth and top of Kodiak tent. Cheers to the golden suggestion of two guy lines per corner, didn't know about that.

Ps figjam starting on your swamp cooler instructions now, thanks!

[Soliton]

Regarding ceiling height:
I'll second the 8' height - lower is better for less wind resistance but 8' was the minimum height for me last year with a 10X10 Kodiak. This year the ceiling was raised to 8'6", because I'm adding angled corner tarps, and, at least for equilateral triangle corners and standard-sized tarps for the angled side walls, there only two reasonable ceiling heights that could be used (the other being around 7')