structural integrity of compact emt shade structure

[vinaych_22]

Hi all,
I am going with a kodiak 10X10 tent to BM and I was looking for shade structure options. I want the shade structure to be compact as I need to be able to carry it in my car. Given this constraint, I figured making my shade structure would be the best bet. I am going with a emt conduit flat top shade structure. To make this structure portable, I am thinking of cutting all the 10' poles into half and using the connector: http://www.canopiesandtarps.com/fffcbcc.html . I am not sure how this impacts the structural integrity of the shade structure.
Here are my shade structure details:
1) Dimensions: 10X20X8
2) This has two 10X10 square structures with each square having its own tarp connected by bungee ball cords
3) all the 7 10' poles on the roof will be cut into 5' (or 4'11") and joined by the connector mentioned above
4) all the 6 legs will be 8' with 5' and 3' sections connected by the connector mentioned above
5) the legs will rest on a foot-pad which will staked into playa ground. I bought the foot pad from http://www.canopiesandtarps.com/accessories-foot-pads.html I have one more question here. Does anyone know if I can drill a 3/4X14 lag screws through the holes of this footpad? or do I need to buy seperate stakes to do this?
6) I am thinking of using a X pattern ratchet straps on the longer sides (total of 4 straps) and 4 more mule-tape tie downs on the corners
7) I am also thinking of using 2 10X8 shade cloths as walls. I am not sure which sides I will be using these. I would appreciate any feedback on this too.
At the far end of the shade structure would be my 10X10 kodiak tent (half inside the shade structure and half outside) with a 10X10 slanted shade cloth covering the tent from the roof of the shade structure.

I will have my partner helping me with the setup. I am fairly confident we both will be able to set up the tent without any problems.

Sorry for the clumsy write-up. Looking forward to your feedback and to Burning Man!! yay!!

[Token]

EMT is not structural to begin with.

Cutting it in half will not help with strength regardless of connector used.

I'd be sure to have a plan B, like a roof rack and a half dozen 2 by 4s with lots of rope and anchors.

[trilobyte]

What token said, for the most part. The conduit won't get stronger as a result of cutting it in half, and the structure won't be able to withstand stronger winds as a result of many connectors. I know of a couple people who do the shorty version of a conduit structure like you're doing (with success), but I think it's probably a smaller structure. There are probably other variables too (they've done full size conduit frame shade before and are good with ropes and tie downs). You've got a reasonably good chance of survival, but in the end you get to be your own guinea pig. I say bring extra rope (in the event you find yourself needing to do any unexpected securing of stuff) and keep an eye on it. Once you've built it and survived the event, you'll know!

[vinaych_22]

Thanks Token and Trilobyte for the replies. I am definitely bringing lot of rope to tie it down. I know many people use EMT conduit based structures and I am not worried about that part. My main concern is about breaking poles and using a connector to make a long pole. On one hand, I feel like having a strong connector should make it less susceptible to winds compared to a single long pole. At the same time, I feel like every new connector makes the overall structure less stable. And If cutting the poles makes it less stable, what can I do to compensate for this lost stability?

On the roof, I am thinking of tying together opposite vertices diagonally to make each square more stable. Vertically, maybe duct tape a 3' rebar at the joint?

I also have an option of using the long poles as is: I have some space in a friend's truck. However in this scenario, I wont be able to test the structure at home. I will have to do it directly at burning man. And that scares me.. And also, I wont be able to use this shade structure at my other camping trips which makes this 380$ structure less versatile.

[Token]

When you make a cut, you increase chance of buckling.

Diagonal strapping will be the opposite of what you want. It will increase buckling.

Best strategy:

1. Try to tie things such that they create tension not compression.

2. For every cut pole, get a 5' length of EMT one size smaller and slide it into each section of the cut pole symmetrically. That will spread the load of bucking forces over greater length of pipe.

3. Use 1 inch or larger conduit as a minimum.

If you intend to use knit shade fabric, it can be deployed as a "stressed member". I. E. Use the shade cloth under tension as a means to hold the shape of the shade structure.

Research tensile shade structures.

A simple tensile is a shade cloth, 4 poles, one at each corner, lots of rope to anchor the corners.

[vinaych_22]

haa!!! that makes sense re: buckling when cut.

1. I think I understand what you are saying. But I am still kind of confused how tension would improve the stability though!! So I try to pull the corners away from the center using ropes? The tarp will try to pull the poles in and the ropes will try to pull it out, causing a stable equillibrium?

2. For every cut pole, get a 5' length of EMT one size smaller and slide it into each section of the cut pole symmetrically. That will spread the load of bucking forces over greater length of pipe:
This is a very interesting idea. I am not sure if the connectors will have a gap inside it. I am hoping they do, in that case, for 5'+5' cut, I can add a smaller 2.5'+5'+2.5' cut which will re-inforce it from inside.

3. I am using a 1' conduit. I saw almost all the conduit based shade structures recommended this size, so went with it

4. hmm . I am using a tarp at the top, not the shade cloth. I want to have some rain protection too in case of rain.

[BBadger]

Mostly you want your structure such that loads cause tension (pull) on elements of your structure, not compression (push). An example would be tension on a guyline, versus pushing on support beam. Compression can cause buckling and can require bracing on the structural element itself, whereas tension relies only on the strength of the element support, which doesn't even need to be rigid.

You can't avoid all forms of compression, such as a guylined pole directing force pushing downwards under lateral force at the top, but you're still predominantly relying on tension on the guyline to maintain structural integrity.

Also, if you can't fit a full tube inside the other tube, the weakest point in a pole, where it'll usually buckle, is in the very middle. If you can prevent that from bowing it'll help a bit.

Here's a nice guide on static rigging.

[EGAZ]

It will add 6 more legs to pack but instead of a coupling, use a Tee fitting and add a leg at each 5' junction.

Run the ratchet straps and lags in a 'compression' fashion to keep it pushed together. In the next pic, the blue line is the cross pipe of your 10' x 20'. Or think of it as half of your structure.

Like This:

compression anchoring1.jpg

It's not ideal & requires more parts to do the job but its a compromise.

[vinaych_22]

I am statring to get nervous about my idea: and it might become very expensive if I have to put a t connector at every joint and one more foot which again needs a connector.
Couple of things I am thinking
1) attach 3'/4' rebar at the pole connections and duct-tape the hell out of it
2) For the legs, put a 1/2" emt conduit inside the 1" conduit to protect from buckling. Basically the 3'+5' 1" emt conuit will have a 5'+3' 1/2" conduit inside it
3) Scale down from 10X20 to 10X10 to reduce the probability of failure and the price

Thanks everyone for the useful suggestions and informatoin

[EGAZ]

Needing to cut everything down to fit the car requires more parts and results in more weak points.

It's really the cutting of the legs that's killin' you the most. And weakening the structure the most. If you can find a way to carry the 8' legs on the roof (requiring a roof rack, 8 sticks for a 10x10, 13 for 20x20) then its only the upper rails that have cuts at 5". With a tee & leg at each junction, it should work with proper anchoring.

Yes, dropping the size to 10 x 10 will help all things, cost/setup/tear-down time/weight to haul/probability of failure/etc....

Or cut everything to 8ft & use an 8 x 8 structure, (if it will still cover what you want) purchase the correct size tarp, (8x8 assuming the usual 4-6" short on each side) carry it all on the roof. No additional tees, not cut EMT sections, solid build just a tad smaller.

But you need a roof rack that can carry the weight of the EMT.

If a roof rack is out of the realm of possibility, then seriously take a look at anchoring a pop up. Not ideal but short of hurricane winds, with proper anchoring it will 'work' - kinda & it will fit in the car.

Or find someone who can haul your structure for you.

That's all I got.....

[Token]

Roof-Rack and don't cut?

Alternatively, make shade smaller.

Big question is: How bad will you suffer if the shade fails?

What is the effort/cost/reward/pain ratio?

[EGAZ]

What is the effort/cost/reward/pain ratio?

The most important one....

[vinaych_22]

roof rack is not a possibility at this time. Thats another investment just for burning man (for me). Being able to carry it inside the car is one of my biggest requirements.

I just requested the retailer to cancel my order for the parts.
If that goes through, I will start looking at some popup canopies and carry loads of wire to tie it down.

Our neighbours (at burning man) bought this

maybe I will get the same one and hope for the best ..


Thanks everyone for the infor

[krly]

Maybe consider a Redneck Roof Rack. Get 2 "pool noodles", run a 1" "cam strap" thru each noodle and the (slightly opened) windows.
Get er done !!
krly

[BBadger]

Have you considered using parts from a carport? The legs are only about 6ft long. I was quite pleased to find out that I can fit all the 6ft long pipes for my carport inside my car (pushing the passenger seat way up; sorry no rideshares!) instead of strapping it to the roof rails or buying an expensive roof rack. Maybe you can do the same.

[gcby30]

Dude, we are doing nearly the EXACT same thing right down to the Kodiak. This thread was exactly what I needed. I'm a virgin so this is one big crapshoot for me. Thanks to eldergeek for that picture, I'm planning on using the tee connectors and a middle leg like that. Really appreciate the diagram.

I was planning to ratchet strap the heck out of my structure with lag screws and a maybe some rebar to keep it all in place. I'll try create a diagram of my intention to post here for critique.

[trilobyte]

The down-side of the setup that eldageekaz' diagram shows is that the structure does not use footpads. Without using footpads, tightening down ratchets may tend to pull the vertical poles into the ground, which could destabilize the structure and make things dicey under high winds.

[EGAZ]

Well I didn't include all the parts. LOL

[vinaych_22]

Hi all, thanks for all the feedback. I scaled down the structure to 10x10 and used t connectors everywhere. I am just coming back from a camping trip where I tested out this structure and am very happy with the result. I have a veteran burner friend who is good with building stuff and he did not have any complaints. Attached are some pictures of the structure and the tent inside. I will be using 6 more ratchet straps to guy it down at playa.

[vinaych_22]

Could not attach more than 3 pics in the earlier message

[Canoe]

... I will be using 6 more ratchet straps to guy it down at playa.

I hope those are for doubling the guylines for each corner. Holds the attachment point to the top of a pole or a tarp corner (or middle) in place much better, so it doesn't thrown around in the wind so minimized dynamic loads. Much more robust.
Double guyline example here. viewtopic.php?t=70367#p1038033