(First storm 2008 - Note the standing waves in the sequential sections. An awning might have limited damage, and did in later version.)
Much of this content was first posted August 22, 2008, just before I left for the playa. 2008 turned out to be the worst week for wind storms I've experienced in my seven years at Burning Man. It was even worse than 2007. I learned a lot in only a few days. This post was updated in 2009 and finally again in 2016.
It's not obvious, but stress is the key to this design in using poly-plastic to create shade AND have it survive up to 80 MPH gusts - or not as the case may be.
The first element of stress is because PVC pipe only becomes somewhat rigid when bent into an arc and held in a plane. Yet it also flexes and kneels when the wind blows. Second, the canvass itself forms a stressed skin structure holding the PVC ribs in their plane. These stresses compliment each other, yet yield to the wind instead of breaking.
Technically this design is an ultra-light, bi-stressed poly shade structure - Poly Shade for short. I believe it's the cheapest, lightest method to shade almost 3000 square feet. It goes up fast and comes down even faster.
Several people have asked how they could build one. Below are detailed construction plans.
As I discovered with the Zen Hammock, PVC is an interesting building material. It's cheap, light, strong, flexible and can be easily worked. That's why, next to duct-tape, it's the most popular building material on the playa during Burning Man.
I decided to use PVC and Tyvek to hold up a LARGE shade structure in 2005. I planned for 70 feet long by 38 foot arch base. The PVC worked fine. The Tyvek didn't. We only got half of it up shading only 35 by 38 feet for a total of 1330 square feet.
Also that first year, I kept each rib in a plane by rigging with ropes. This was too complex and the ropes wore holes in the Tyvek fabric when buffeted by the wind.
In 2006 I switched from Tyvek to poly-tarp and dropped the rib to rib ropes. Instead, I used the fabric itself attached with ball-bungees to hold the ribs in a plane. This simplification turned it into a stressed-skin structure which worked well. I also spread the base to 40 feet which dropped the top of the ribs just enough to reach from the motor-home.
In 2006 we used five ribs and four sections of twelve foot wide tarps. This gave us a foot print of 40 feet by 50 feet (including PVC width), for over 2304 square feet of shade.
In 2007 I expanded the length one more section giving us just over 60 feet by 40 feet and 2880 square feet of shade. I also replaced the side PVC with simple rope anchors, but poly-stressed was about to take on a whole new meaning.
2007 had the worst and most consistent winds with the largest gusts of any year I've been at Burning Man (until 2008!). Once we finally got it up (wind problems), the structure flexed and kneeled in the wind all week. Thursday and Friday brought a thunderstorm each day. By the end of the week, one t-post broke off right at the playa and another had pulled out of the ground. Many of the grommets had pulled out and tarp was flapping in the wind. The design had been out to the limits.
The biggest problem was, because of the wind, we didn't get a good initial rig and the ribs were out of plane. The structure kneeled right away pulling grommets out. Once weakened, it just got worse. More rigid ribs would also have helped.
In 2008 I plan to increase the internal links from 4 to 20 feet on the end ribs and 4 to 10 feet on the rest of the ribs. I also plan to extend it one more section to over 72 feet giving us 3456 square feet of shade and making it finally larger than my original design.
If you've read my Burning Man blog post for 2008, you know 2008 was worse than even 2007 for wind, and it wasn't short-term thunderstorms that caused the problems. It was sustained strong winds for hours on end. Sunday's storm was moderate, but still pulled apart the first and second ribs on the windward south end.
I had used the new design with longer links so I didn't think I needed centering tape. Looks like I was wrong. Ten or even twenty foot links can shift around with enough bouncing. And then they come apart at the weak point. We lashed things down as well as we could Monday morning just as the wind picked up again.
Monday's storm was far worse. It's 30 to 40 MPH winds went on for most of the day, all night and even into the next morning. They had to close the gate to Burning Man for six hours because of total white-out that evening.
(2008 Sunday / Monday Storm Damage)
By Tuesday morning there was little of the Poly Shade structure left standing. We took it all down except for three ribs which were still in fair condition. On Wednesday, we moved the few good tarps onto these empty rib sections. To help some of the camps in the sun, I also added an awning to the windward end. Not only did it provide extra shade, it seem to help keep the wind out of from under the structure, so it didn't jump as much when the next big storm hit on Saturday. Was this a clue?
My plan for 2009 is to return to the three rib design but on 16' centers as tarp weight does not seem to be a limit. The 20' links seem to just add more weight than rigidity. I will use 10' links and center-tape them as in earlier designs.
The biggest change will be awnings on both ends, plus four end ropes instead of three. This should hold the plane better. We'll see. Instead of joining the tarp sections with tie-wraps this year, I'll only join the corners. Then when on the playa, I'll thread a50' x 1/4" poly reef rope along each seam and tie it to the tarp corner at the anchor end. The other end will go over the center rib and allow for reefing of the awnings and to some degree the center sections as well.
I also plan to install the safety x-ropes from the top of EACH rib to the tire on a motor-home or other vehicle. This should cut down on the "galloping" as well as insure the whole thing doesn't blow down playa.
Another line of defense against strong predicted winds is to add the ability to "reef" much of the canvas. My idea is to thread poly rope along the seams of the tarps in an "accordion" fashion so I can release the base of the awning tarps and pull and bunch them to the center rib.
My plan is to reef the trailing edge first, then the leading edge. This should reduce canvas by 50%. If it's going to be a bad blow, I could also release the end ropes and pull the ribs into the center rib using the reefing ropes. This should cut tarp area by a total of 75%. I'll let you know how all this works out.
Materials 2009 Design
Each Description Cost Weight 8 5' steel t-posts 40 48 6 14" sections of 3/16" steel chain 12 6 Chain QuickLinks 12 9 20' x 2 1/2" S40 PVC for ribs 225 243 6 10' x 2" class 200 PVC for links 3 x 20' 45 36 6 4' x 1 1/2" class 200 PVC = 2 x 20' foundations 22 6 4' x 2" class 200 PVC = 2 x 20' foundations 34 16 12' x 16' Costco 10mm poly tarps 144 112 72 8" Tie-wraps 4 300 8" Ball-bungees 75 6 1/4" poly X-ropes (6 x 25' = 150') 20 6 1/4" poly side-ropes (6 x 10' = 60') 10 6 1/4" poly reef-ropes (6 x 50' = 300') 40 8 3/8" poly end ropes (8 x 50' = 200') 16 8 Tension straps 80 10 Safety lights 40 Total $819 439 pounds Site Tools 100' tape Fence post pounder Saw Hammer Fence post puller
Drill a 3/8th inch hole in the top of the flange of 6 five foot steel t-posts. Use a screw link to add 14 inches of 1 1/4 inch chain to each flange. This is where the side-anchor ropes will attach.
Cut 6 each of 1 1/2 inch class 200 PVC four feet long. Cut the same using 2 inch class 200 PVC. One each of these sleeves will fit over each steel t-post creating two internal layers to distribute the stress and keep the rib from splitting out at the bottom. These three elements make up the "foundation".
Each rib is made up of three 20 foot 2.5 inch S40 grade PVC pipes. An internal 10' "link" of 2 inch class 200 is used to distribute the stress at each joint. For the first three years, this link was four feet long. In 2009 I'm using 10 foot links. This should make the ribs more rigid but still light-weight.
Cut the six inch flange off of three 20 foot class 200 2 inch PVC sections. Cut them in half of as (just under) 10' internal links for the center ribs. Wrap six layers of duct tape at the center of each link, staggered over a five inches of pipe to form ramped peak of tape in the very center.
Black mark the center as well as 4 inches in from the non-flared end of each S40 rib section.
Load for transport - I had room to put them inside my motor-home but I had to crawl over top of them so load them last. If you load them on a roof as I did one year, note their total weight and the effect it has on handling. I could feel it. Also make sure the load is secure.
Drag out the tarps and grade for similar size along the 16 foot sides. Try different combinations until the corner grommets line up, as size is inconsistent with these cheap tarps. Alternate colored sides if you want a checker-board pattern when you're done.
Fold up tarps and strap with tension straps.
Load for transport.
Pick a site where the center-line of the end anchor ropes will point to Gerlach if at all possible. That is where the most common winds come from. The point is to have the wind go up and over the awning structure instead of hitting the side.
Plot a line 92', 9" long with the ends as the end rope anchor points. At 30' in, swing a 20' arc about 90 degrees to the long line. Next sweep a 36' arc from the closest anchor point. Set a corner post where the two arcs cross. Repeat for each corner.
The center rib post should be midway between these corner posts at 16' 1.5" on each side. This should yield a rectangle just over 32' x 40' as a footprint for the structure. Measuring corner to corner at 51.22' to make sure it's on the square.
Drive in all rib posts vertically 16" or until firm, keeping chain above ground.
Drive in end anchor post at 50 degrees from the ground so the rope vector will be less than 90 degrees to the post, and therefor pull it IN to the ground.
Place 4 foot 1 1/2" and 2" foundations sleeves on all rib posts.
Assemble all ribs with 10' links.
First wrap the center of each link with 5 wraps of duct-tape beveled off along the sides of the wraps.
Mark small end of rib at joint 3" from the end. Using a wooden block, hammer ribs together until they approach the 3" mark. Duct-tape the outside of the rib joint to hold them in place until they are under stress. They will get tighter once the wind starts blowing.
There are lots of good knots. At times I've used a clove hitch, but most of the times just plenty of half-hitches.
Tie end ropes to end ribs at 15' and 25' from each end of the rib.
Add two X-ropes at one third points along the ribs (see Storm Management below).
Setting the Ribs
Place all ribs to the outside of the foot-print next to their posts ready to move into place. Drive the motor-home into the center of the footprint.
Raise and drape the first rib across the top of the motor-home.
With one person on top of the motor-home to stabilize the rib, one guy at least six feet tall to hold high, one guy to guide the end over the post, and up to two others for muscle, place the rib over foundation post on one side, and then the other.
Setting ribs is a tricky process. Using ropes, I actually placed one of these by myself once, but it's VERY difficult alone. With the right crew, it's quick and easy work. The key is cooperation. It's like lifting a piano - not as heavy, but more awkward. The rib seems to move on it's own like a huge snake until it's seated. The key is to work together, and don't ever leave just one guy holding all the force. These ribs can kick like a mule. It's not as bad as I make it sound - it's just a different kind of physical experience.
Back up motor-home to next rib position.
Repeat for all ribs.
Add a tension strap to each end rope and attach it to the anchor post, but leave it slack until tarps are in place.
Setting the Tarp
Wait for calm. This is important. Flapping tarps are difficult to bungee and pull tight. In the wind, you'll end up with a poor alignment and a weaker structure. I've done it.
Layout a tarp section for one of the center positions. Thread a 50' x 1/4" poly reef rope through each of the three seams. Pull the motor-home forward and drag the tarp section on top.
Line up tarp center seam with rib center mark to place first bungee. Or you can offset tarp to get more shade (or wind load) on one side or the other. Make sure any offset is the same on both ribs to keep things square.
Bungee from the center down each side pulling tarp tight as you go. If you can, work both ribs of the tarp at the same time to make sure it stays square. When a center section is done, secure the center end of the reef rope and thread the anchor end through the cooresponding seams of the awning tarp section which should be on the top of the end ropes. Secure the reef rope at the anchor end of the awning. Pull awning up on the motor-home and bungee to the end rib keeping it tight as before.
Repeat for both ends.
Add string lights to ribs inside structure to suit your taste.
Release lower end-ropes and pull to the side to drive in and park vehicles. I drive over an old tarp to use as a floor. Replace end-ropes.
Secure the two x-ropes of each rib to the tires of vehicles. Tying around the bottom of car tires works well if the rope angle won't rub the paint or wear against metal.
Adjust tension straps on end ropes to take any slack out of structure, but be careful that END RIBS REMAIN IN A PLANE and vertical. If the end ribs get out of plane, they will kneel in lighter winds and do more damage to the grommets.
Rig side ropes from tarps to post anchor chains making sure all slack is out of tarps.
Put PVC over end anchor posts for safety.
Add safety lights to end ropes at eye level and anchor posts.
Total playa construction should have taken about six hours.
Have a good Burn! :)
Depending on wind direction and strength, there are things you can do to improve safety and mitigate damage. Orienting the structure so the wind goes THROUGH the structure instead of against the side is the most helpful thing - (WRONG 2008 advice. Instead, use awnings to get the wind to go UP and OVER structure so that standing waves and oscillations don't start. This was learned in 2008 and is the approach I'll use in 2009).
If winds go over 30 MPH, you are likely to get "kneeling" where the ribs will deform, leave plane, and pull into an "S" shape in three dimensions. You'll know it when you see it.
Unless, the ribs are banging on something below, this will do little or no damage. The rib will pop back up on its own when the wind dies down.
If the wind goes over 40 MPH or you have bad gusting, you may get "galloping" where the ribs and tarps move in waves down the structure. This will tend to stress the posts, foundations, ribs, joints, grommets and tarps. I've even tied ribs down into kneeling position during bad storms to cut galloping and stress. (Let's see how awnings help this problem).
With bad galloping, I've seen the ribs jumping up their posts and off the playa more than a foot in bad storms. This is usually because the side rope grommets have pulled out or other damage has been done. Once things start breaking down, it just gets worse.
In 2007 one post broke off at the playa and another pulled out completely from galloping. In both cases, I added X-ropes to keep the rib secure and somewhat in position.
One important safety point to note is, if a post breaks or pulls out of the playa, it will want to jump out and may hit anything in the way (car, tent or someone's head).
Keep the area around the rib posts clear for this reason. Usually the rib (and post) will only jump a couple of feet and then dig into the dirt again. The tarps and bungees tend to hold it in form. But it's better to be safe and NOT take a nap next to one of these ribs in a storm. A tent will NOT slow it's kick much.
Tear-down goes much faster than construction.
Release end ropes. After a week in the wind, the ribs will probably sag over to the sides.
Hang on ribs and pop bungees off.
Fold and strap tarps.
Place one guy on top of motor-home to stabilize ribs as before, while up to four others lift them off of foundations. One person should grab and hold the PVC foundation sleeves down as the rib comes up so you don't have to lift as high to get them off. Watch your fingers as it pops off.
Another VERY important safety point here is these ribs may kick like a mule once they clear the post. Make sure AT LEAST two people have a firm grip until they are laid down.
Repeat for all ribs.
De-constructing the ribs can be difficult depending on how much pounding the wind did during the week. Use the motor-home to pull them apart. Tie a rope to the back of the motor-home and to one end of a rib. Tie the other end of the rib to one of the end posts. A timber knot or several half-hitches will usually do it. Drive the motor-home ahead slowly and they will generally pop apart. This process will take a while but works well and is safe if you stand well clear of the joint as it pops apart. One rib would NOT come apart after the storms of 2008. We broke two ropes and a STRAP trying. We finally sawed it in two.
Secure load for transport.
If you have any questions, please email so I can also update this post with your feedback.
And let me know how it works out if you give it a try.
In 2010 I made smaller ribs by only using two 20' PVC sections with only on 10' link. this yielded only 25' wide base but also created a lower and more rigid structure which seem to stand up to the wind better. The tarp awnings on each end also helped keep the wind from doing so much damage. Well, once we got it in place.
As is common on the playa, the wind came up before we got all the tarps on. We had to stop work. And then it got worse. By the next morning we had rain and a fair amount of tarp damage. As soon as things dried out, we took the damaged tarps down and started over. This time we got it stable before the next storm blew in. Yep, it blew hard and rained again, but this time everything held up with no problems for the rest of the week.
This year (2011) I plan to use the same design except add on more rib for another 400 square feet of shade. I'll let you know how it goes.
Materials for the 2011 Design
Each Description Cost Weight 8 5' steel t-posts 40 486 14" sections of 3/16" steel chain 126 Chain QuickLinks 128 20' x 2 1/2" S40 PVC for ribs 200 216 6 10' x 2" class 200 PVC for links 3 x 20' 30 36 8 4' x 1 1/2" class 200 PVC = 2 x 20' foundations 29 8 4' x 2" class 200 PVC = 2 x 20' foundations 45 10 12' x 16' Costco 10mm poly tarps 100 70 48 8" Tie-wraps 5 96 8" Ball-bungees 30 6 1/4" poly X-ropes (6 x 25' = 150') 20 6 1/4" poly side-ropes (6 x 10' = 60') 14 6 1/2" poly end ropes (6 x 25' = 150') 18 6 Tension straps 60 10 Safety lights 40 Total $671 382 pounds2 5' steel t-posts (no chain) for end anchors 16 12
Plot a line 88', 7.5" long with the ends as the end rope anchor points. At 20' in, swing a 12' 6" arc about 90 degrees to the long line. Next sweep a 23' 7" arc from the closest anchor point. Set a corner post where the two arcs cross. Repeat for each corner.
Repeat this process for four ribs at 16' 2.5" on each side and 12.5' from the center line. This should yield a rectangle of 48' 7.5" x 25' as a footprint for the structure. Measuring corner to corner at 54' 8" to make sure it's on the square.
Another change we made this year was to "reef" the tarps during bad storms. If you simply push the bungees together on both ends of the tarp, it gathers in the center where you can wrap bungees around the bundle. It obviously provides no shelter in this configuration but will withstand very high winds with no damage. Then just redeploy the next morning when the wind dies down.
One final change we made was to use three tarps on the smaller 40' ribs with the top tarp overlapping the side tarps by two feet on each side. This worked very well when we got a half inch of rain in 2014. The water shed nicely.
Let me know if you use this design or have any questions.