Introduction: A Big, Luxurious Stretch Tent for Burning Man
For Burning Man 2016, the Luxurious Vagrants built a big, communal stretch tent that we used for chill hang outs, throwing events, and projecting artwork.
Step 1: Design
The year, my burning man camp, the Luxurious Vagrants, wanted to create a unique center structure that would serve as a relaxed hang out spot, a communal space for activities, and a canvas for projection artwork.
Of course, Burning Man creates its own set of unique design constraints. The structure has to be easy to pack and move out to the desert, relatively simple to assemble, fairly inexpensive (we’re only using this once a year), and most importantly, structurally stable in a high-wind environment.
After many iterations, our camp designed a pentagonal stretch tent structure.
The design features:
- one central structural element: a 20’ tall antenna tower triangular truss bought off the shelf.
- 5 guy lines anchored to the ground
- stretch fabric connecting in between the guy lines to create a shaded area
We did all of the CAD design for the structure in Autodesk Fusion 360 (screenshot pictured).
Step 2: Playa Engineering Strategies
There were three engineering challenges that were critical for the structure.
- Creating “the weakest point” into the structure.
- Our primary engineering concern with building this structure was to limit the possibility of a large gust of wind toppling the central structural element and and hurting someone. To guard against this risk, we over-engineered the guy lines with thick steel hardware and under-engineered the connections between the shading elements to the guy lines (we used zip ties). That way, if a huge gust came along, it would pop off the shade fabric, which would then reduce the wind load on the structure.
- Quick, on-playa assembly.
- It's no fun to spend half the week setting up your structure. So - we wanted to make the structure easy to assemble. In the end, we were able to get the structure up in a single afternoon with 6 or 7 people helping.
- Playa anchoring.
- Playa anchoring is a highly discussed topic amongst the Playa MacGyver's out there! See this thread on ePlaya (659 posts and counting...) if you're intrigued to learn more about all of the various strategies.
- We used a total of 19 24” lag screws — 3 at each guy line and 4 at the base. We drilled them using a cheap, corded Impact Driver from Harbor Freight. None of them moved an inch throughout the week.
Step 3: Selecting, Purchasing and Testing the Antenna Tower
Selecting the antenna tower was relatively straight forward. We looked over options and eventually ordered a 20' AME-25 tower from DXEngineering.com. Delivery took about 2 weeks.
We bought 2 10’ segments (which bolted together) and a hinged base (the 20' segment bolts onto a hinged mount). We sprung for the hinged base to make assembly easier. The hinged base had 6 pre-drilled holes that were slightly bigger than the the lag screws.
When the antenna arrived, we quickly set it up for a test run. It's huge! : )
Step 4: Guy Line Hardware
We over-engineered the guy hardware. Everything was sourced on E-rigging. Again, the goal was for the major weight bearing elements (guy lines, anchors, and tower) to fail last (and the shade fabric to fail first).
Each guy had:
- One large hook to connect the guy line to the tower
- A 1/4” steel cable that made up the majority of the guy line
- A 3/8” turnbuckle at the bottom of the guy line
- 2 or 3 links of steel chain to connect the turnbuckle to the anchoring lag screw.
We assembled each guy line before heading out to the playa. This included swaging the steel cable and attaching the cable to the turnbuckle and hook.
Step 5: Making the Ground Anchors
To really over-engineer things, I decided to use 3 24” lag screws per guy line. Of course, in order for 3 anchors to support 1 guy line, the 3 anchors need to equally support the load.
To that end, I decided to make, for lack of a better term, "ground anchors" - which were simply flat steel extrusions with 3 holes for lag screws. The guy line was connected to the anchor using two links of steel chain that went through the center lag screw.
To build the ground anchors, I scavenged a long carbon steel extrusion that just happened to have holes alrady drilled into it at regular intervals. I was able to cut that piece using a horizontal bandsaw into 4 anchors. For the fifth anchor, I found a scrap piece of rectangular steel extrusion (appears to be stainless?) and drilled 3 holes into it as well.
Step 6: Water Jet Cutting the Tower Mounting Plate
Our central structural tower is triangular, but we were trying to attach 5 guy lines. Unfortunately, that means there aren’t 5 equidistant points to mount the guys onto the tower. Fortunately - I had access to a massive water jet cutter at Pier 9. I designed a steel mounting plate with 5 large holes to hook in the guy lines and 5 smaller holes to attach the top of the 5 pieces of shade cloth.
The plate was held firmly in place on the top of antenna tower using 3 bolts.
Step 7: Design and 3D Printing the Diamond
Of course, we needed a beacon on top of the tent to guide our wary souls back to camp. Given that we're the Luxurious Vagrants, we naturally went with a 4’ tall diamond.
To reduce wind loads, I decided to design the diamond as a thin frame, which we would then illuminate with LED strips. The downside of this design is you can’t really see it during the day.
I built the diamond by 3D printing joints that were connected using 1/4” wooden dowel. The 3 center joints were connected using a 4’ long 3/8” diameter threaded rod. 3/8” bolts were glued into the 3 center joints, allowing the joints to be threaded onto the rod. The rest of the joints and dowels were then assembled. The dowels fit into the joints with a press fit, but we also taped the joints on site to make sure they didn’t come apart. The entire diamond assembly was bolted onto the top plate using two nuts
The joints were 3D printed out of ASA on a Stratasys Fortus printer. They could definitely be printed with a cheaper printer such as an Ultimaker or Makerbot.
Step 8: Shade Fabric and Joints
For the shade fabric, I went to our local discount fabric store and surveyed the options. I ended purchasing about 40 yards of white, two-way stretch shade fabric for about $5 / yd. The fabric was way, way stretchier that I expected - about 70% in both directions - and we ended only using about half of what we purchased.
To connect the fabric pieces, we used the "no sew method". We used marbles instead of pennies.
We designed the triangular shade pattern to minimize waste and cutting. Each pentagonal shade face was composed of 4 triangles.
Before heading out to the playa, we cut the shade fabric and assembled them into the 5 pentagonal sides using the marble method.
Step 9: Heading Out to the Playa
After prepping the guy lines, diamond, tower, ground anchors, and shade fabric, we were ready to head to the playa.
Step 10: Erecting the Tower
Before erecting the tower, we
- attached the guy lines to the top plate
- attached the 5 shade cloths to the top plate
- pre-attached the shade cloth to the guy lines using zip ties.
- anchored the hinged base into the playa with 4 lag screws.
- wired LED lights into the diamond and through the center tower.
- added our fabric “skirt” around the central tower.
Erecting the tower was actually very easy. 3 people manned paracord ropes while 3 others walked the tower up into plate. We then locked the base into place using bolts.
Step 11: Anchoring the Lag Screws Into the Ground
Next, we anchored the guy lines into the ground using the anchor hardware, lag screws, the harbor freight impact driver, and lots of patience. The first 18” inches into the ground was a breeze but the last 6” was a real pain. We ended up having to put our entire body weight onto the driver to get the lag screws in those last 6” inches.
Step 12: Fixing the Shade Cloth to the Guy Lines
To attach the shade cloth, we attached a 100’ long 1/8” steel cable around the perimeter of the structure, 8 feet off the ground. The 1/8” steel perimeter cable was attached to the 1/4” guy lines using U-clamps. We used a turnbuckle on the 100’ cable to get it nice and tight.
After getting the perimeter cable and U clamps in place, we attached the bottom points of the triangular shade to the guy line using some paracord.
Step 13: Tensioning!
Don’t forget to tension! We went around with a couple of wrenches and tensioned each guy.
Step 14: Electronics and Lights
For the finishing touch, I connected the bottom of the LED electronics up to power. The top diamond LEDs were connected to a battery pack - so the diamond would be on even when we turned the generator off at night. For the center tower, I used two 18’ long multicolor, controllable LED strips that I taped back to back and hung straight down the center of the tower. The skirt diffused the light nicely.
Step 15: Project Mapping
Finally, Matt Bush set up two projectors and fired up his software. Before heading out to the playa, Matt designed the specific geometry of the shade fabric into his software. Notice, for instance, that there's no projection on the center pool, even though the the projections are coming from the direction of the camera.