Stone 7 at AfrikaBurn

Most of the focus has been on Stone 27 the project for Burning Man, but the work on Stone 7 for AfrikaBurn is going to start in just a few days! Couldn’t be more excited! Benjamin, Mae, and Monica will be heading to Cape Town next week to begin fabrication and staging for the project! There’s a lot to do! Fabrication will start right away, we need to find and prep our stones, as well as gather all the other necessary equipment. Expect updates as it comes together, but if you would like to follow along @stonetwenteyseven on Instagram will be sharing the story as it happens.

Also please consider donating to the project. We we super grateful to get a grant from AfrikaBurn to create the project, but we are still trying to raise an additional $2000 to cover the costs of materials, fabrication, and transportation.

Ben Langholz
Fabrication specifications!

Last night Amihay finished up the initial spec for the details of fabrication for our columns! This is super exciting. While we know they will likely change before it’s time to actually build them out, this will allow us to reach out to some fabrication shops to get a quote for the work.

We have been working under the assumption that fabricating ourselves would while be more labor intensive, be the cheaper. Now we can get some numbers to make a real comparison and inform our decision.

Anyone know a good fabrication shop in Reno? Please let us know!

Screen Shot 2019-03-27 at 1.42.16 PM.png
Ben Langholz
A test! We learned some things...

We spent last weekend with steel, stones, and rain. We learned a lot from this test.

  • The stones we would likely want may not be so heavy. The larger of the two we used while it was a bit flat weighed in at 195kg about 430lbs.

  • The bolts we got as a gift from Jim at Bolt Products (Thank you Jim!) worked amazingly. We did decide though that the larger bolts were a bit too big and looked funny coming so far out of the stones. Jim is working to get us a set of bolts with an eye half the size for AfrikaBurn.

  • Drilling the holes was a bit harder then expected on the larger stone and took some serious muscle. We also wore out a Bosch drill bit by the end of the 10th hole.

  • Air compressor is much better to blow out the holes then the hand pump or mouth options.

  • The glue set within a few hours, even in the rain!

  • We got a good idea of the spacing we want between stones, and a final rigging configuration for AfrikaBurn.

  • The come alongs worked great!

come dance gif.gif

Sadly the frame we built had trouble to support the horizontal rigging forces we wanted to apply to the stones. Some of the pipe that was bracing the frame bent so we had to try a different configuration for the rigging lines in order to get an idea of spacing we would want between stones.


It was super nice to walk between two stones for the first time!

Ben Langholz
Numbers numbers numbers!

Amy Kordosky our super engineer in San Francisco delivered this intense 173 page document of numbers! This is the start of our FEM Finite Element Analysis which will help us determine the appropriate steel sizes and thicknesses, number of ground screws, strength of wire rope required, and many other details of the design. Different kinds of loading, and wind testing is also applied. Overall it means the structure won’t fall down or collapse when Mayan Warrior pulls up to play next to it.

structural gif.gif


  1. Columns: Members 1-7, sized as 5” diameter tubes, 3/8” thick. Material is A500 Grade B steel (Fy=42ksi)

    1. Max compression: In member 1 (middle column): 31 kip (compression)

    2. Max moment: In member 2: 0.35 kip*ft

    3. Member capacity: Compression = 38 kip, Moment = ~25 kip*ft

Demand-to-capacity ratio = 31/38+.35/25 = 0.83 (< 1.0, okay)

  1. Wires: Members 8-113, sized at 3/8” diameter. Material is A416 Grade 270 (Fy=270ksi)

    1. Layout: Currently have 3 wires connecting each rock to the columns and/or ground. Also, I have each rock connected to its neighboring rock with a wire (I did this for stability in the model. I don’t think we will need to connect every rock, but I do think connecting some to each other might be helpful. I still need to explore what wires are really needed, and plan to do this once I get the accurate model coordinates from Amihay. A fair amount of wires are currently shown to take no load, meaning they would be in compression, and not helping the structure).

    2. Max axial force: In member 10: 3.6 kip (tension)

    3. Member capacity: Tension = 28 kip

Demand-to-capacity ratio = 3.6/28 = 0.13 (< 1.0, okay – can downsize diameter or get weaker wire if loads stay this low with different wire configuration)

  1. Loads: 

    1. Dead load = self weight of materials + weight of rocks (assumed 1200 lbs.)

    2. Live load = weight of humans (assumed 500 lbs. on each rock)

    3. Wind load = 7.5 psf pressure, equates to ~ 47lbs. on each rock and 3.75plf along each column

  1. Base Reactions:

    1. Max Compression: 31 kips (joint 1- base of center column) 

    2. Max tension: 2.2 kips (joint 12)

    3. Max shear: 2.1 (joint 6)

Ben Langholz
Gearing up!

Gearing up for a 2 Stone test this weekend! Look at those sexy stones and rigging hardware 😍

Stones are about 80cm in diameter.

We’re hopping to test out our bolting process and verify we want to use them at AfrikaBurn and Burning Man, experiment with the spacing between stones and see how much space we can have an still step from one to another, and do some stability tests to learn more about how many wires we need per stone.

Ben Langholz
Planning for funds

Ann-Kathrine and I got together for a super quick super productive brainstorm over fundraising and a crowdfunding video. 



We watched a lot of Burning Man crowdfunding videos and decided they were all a bit too heavy and serious. Keep an eye out for something fun coming from us!

Ben Langholz
Beginning A Test

Amihay and I spent the day in Brandenburg starting work on the test, Stone 2? It will be a frame to support 2-3 stones and we hope to test out the new glue-in bolts, our hardwear configuration for the wire ropes, and the stability of the stones with a variety of bolts and anchoring combinations.


I got schooled on welding and learned a ton! My very first attempts were chunky, but I started to get the hang of it pretty quick. 


We decided that we’re going to try to bring Stone 2 to Kiez Burn in June as an installation! Super exciting 🚀

Ben Langholz
A Work In Progress

We’ve been hard at work for weeks! Amihay joined the project as Engineering lead early on, and we have been working side by side for the past few weeks to create the scale model, start getting an idea of the member sizes, and design out the fabrication details. Amy recently joined our growing crew and is currently design the digital structural model in order to run load tests and confirm our calculations. Next step is building a scale test in Amihay’s back yard in Brandenburg Germany. We’re both looking forward to stepping away from the computer and getting our hands dirty with some welding! Follow Stone 27 on Instagram or Facebook to see our progress.

Screen Shot 2019-02-28 at 7.15.51 PM.png
detail 21.jpg
detail 2.jpg
Ben Langholz