Bamboo Dome

Years ago I found plans on how to build a bamboo dome and the idea got stuck in my head. Nobody was building domes like this (even now I can only find two examples that even use the same principle) and I wanted to try.

I started with a scale model about 1m across (instructions for the mini-dome are in a separate section), and over the years I managed to build a big one (6m across) at various Burning Man regionals, refining my technique with every build.

I found this dome to be just as stable as the common 'vertex' style you probably know, but much lighter (weight/size - ~20kg for a 6m dome, fits in two large bags) and easier to build (very hippie friendly).

For the curious there's pictures of the whole journey here.

A few notes on the general principles:

The bamboo follows circles on an ideal sphere, intersecting at two angles (referred to here as Red and Blue crossings) and overlapping at the halfway point between crossings: R--=--R--=--B--=--B--=--R--=--R--=--B--=--B etc. This forms regular pentagrams with Blue corners, surrounded by hexagons with two Blue and four Red corners, .

A full circle has 20 crossings, so the angle between struts at the overlap is about 9°.

A strut is either (Overlap)(Red-Red arc/2)(Red Crossing)(Red-Blue arc/2)(Overlap) or (Overlap)(Red-Blue arc/2)(Blue Crossing)(Blue-Blue arc/2)(Overlap) - (=r--R--b= and =r--B--b= for short). There's also 10 half-struts of each color at the bottom (pointing toward the ground): =r--R and =r--B.

This technique can be used to build any number of shapes with similar geometric properties.

Supplies

• The dome:
• Bamboo (~100x 240cm yellow Moso)
• Reusable cable ties (~300x 350x7.5mm, rated for 50kg tension)
• Red and blue colored gaffa tape (two rolls each) for marking the bamboo
• 10m rope x2
• Tent pegs (10x shaped steel, the ones you can hammer in without risking bending them)
• The canopy:
• Camouflage netting to cover a 10m diameter circle (in my case 1x 6x6m, 3x 4x5m)

Everything is reused, but expect about 10% breakage/loss of bamboo and ties during the first few builds as hidden material defects become apparent under load.

Using a canopy with a continuous surface (parachute, tent, canvas, or similar) can grant protection from rain at the cost of risking the dome getting deformed/squashed in strong winds - the dome is flexible but the materials have a limit.

I'm working out how to make a rainproof canopy that still allows the wind to pass through. I'll add it here when it's done.

Step 1: Preparing the Materials

*All lengths are for 240cm poles and 15cm overlap

The spreadsheet with the formulas to calculate the strut/pole lengths for a desired dome size (or the dome size given a pole length) is here.

You need two lengths of struts, referred to as 'Blue' and 'Red', their combined length (including some overlap at the ends) should be the length of your starting poles.

Cut the bamboo to size

You'll need 70 struts of 115cm (Blue), 80 of 125cm (Red), 10 each of 63,66cm (Red/2) and 61,27cm (Blue/2)

I recommend preparing 10 spare long struts of each color. If you started out with 100 poles, this leaves a few whole poles you can use to prop up/raise the dome during build.

The most economic way to achieve this is as follows:

80 poles cut 125/115cm

10 poles cut 125/65/leftover

4 poles cut 62,5/62,5/62,5/leftover

Mark the bamboo

Mark the crossing points with a narrow strip of tape in their respective color, wound twice around the strut, and the overlaps with the color they point towards. The distances (in cm) are as follows:

(15)R(46,27)B(38,81)B(15) for the short (B) struts

(15)B(46,27)R(48,66)R(15) for the long (R) struts

For the half-struts the markings are

~B(38,81)R(15) and ~R(48,66)R(15)

Tie the struts with some spare ties into bundles of 10 of the same length for easy handling.

Prepare the cable ties

Pre-connect the cable ties in a double loop as pictured. You'll need 280 (60 for the crossings, 220 for the 110 overlaps), as above I recommend making enough spares.

Prepare the canopy

You need to cover a circle 10m across to drape over a dome this size (I attached the stitching pattern I used). You should mark the center for later.

Laminate the instructions for easy reference during build (attached)

Step 2: Building the Dome

It's easiest to do this as a team of 5, in the optimal case it can be done in a few hours. Only one person needs to understand the whole process, the actual build is easily broken down into simple repetitive tasks.

Cross Assembly and Tying

Connect pairs of struts of the same color at the crossing point, starting with the (short + long) pairs of the bottom ring.

• Lay a long strut over your knees, so that the end of the same color as the middle is pointing right
• Hang a tie over the crossing (middle) marking so the two loops hang down on opposite sides of the strut
• Push a strut of the same color through the two hanging loops (crossing under the strut in your lap) with the Blue end pointing forward and the Red behind until the crossing points are aligned
• Pull the tie closed tight enough that the struts can't slide freely
• If you first make a cross each of R+R/2, B+B/2, R+R, and B+B you can have your helpers just copy them exactly until you run out of struts :)
• Pile up the crosses like with like

Dome Build

1. The Crown:
2. Tie together two B crosses as shown in in the diagram. Note that the end measuring points have the same designation as the cross to which they are connected. The struts should always alternate sides at every overlap (the diagrams show this, but it's worth pointing out :)
3. Add two more B crosses in the same manner as shown in step A.
4. Add fifth B cross between the untied legs. In order to insert this cross, all crosses will be twisted so that a regular pentagon is formed.
5. The second stage consists of closing the five triangles around the pentagon. Use 5 R crosses. Again, the end measuring points always have the same designation as the cross to which they are connected.
6. At this point, the structure will tend to bow. Turn the figure so that it is concave downward.
7. Lift the assembled figure off the ground to facilitate the addition of new crosses. Use five bi-ped props. Each prop consists of two bamboo sticks, tied together near the top with a cord about a foot long. These props will then support the dome at equidistant points from it's apex; first at the five vertices at the top of the pentagon, later at five corresponding points on the top five hexagons.
8. Walking around the structure laying out the crosses for your helpers to attach can make this go really fast.
9. For the third stage, use 10 R crosses as shown.
10. The fourth stage uses 5 B crosses which close the five hexagons.
11. Canopy: You should spread the canopy over it at this point.
12. The fifth stage uses 10 B crosses to close ten triangles. Six of the crosses can be seen in the diagram.
13. The sixth stage uses 10 B crosses and 10 R crosses to complete the first horizontal band. We now have a 3/8 dome.
14. Girdle: Thread and tighten a long loop of rope through/around the horizontal ring
15. The seventh stage uses 10 R crosses and the eighth stage uses 10 R crosses and 10 B crosses. On the last twenty crosses, use the crosses with half-poles pointing to the ground.
16. Anchors: Thread and tighten a long loop of rope through/around the bottom horizontal ring. Anchor the bottom ring to the ground.

Step 3: Disassembly and Transport

Start by separating the dome into two parts

by undoing the bindings between stages 6 and 7 (just below the upper ring/girdle - you'll need 5 people to hold the upper ring steady while this is happening) and lowering the upper part to the ground you can minimize uneven load on the structure and reduce the risk of breaks during disassembly.

Disassemble the bottom ring

Start at the top, loosening ties and removing struts as you go around the structure.

Disassemble the crown

As above, keep removing struts from the bottom until it's all gone. Best to do this from five sides at once to keep the load even, or use the props from the building stage if you still got them.

Gather the canopy from the outside in, one bit at the time while you do this.

Gather and store the pieces

Step 4: Mini-Dome

To build a miniature version of the dome (also great fun for kids) I used 30cm skewers (cut into 14,4/15,6 segments) and dental floss. The resulting dome is about 73cm across.

The process is the same as for the big one, minus the canopy (a fitted sheet can be used at this size).

The measurements and markings (in cm) of the sticks are:

Blue: 2,00(B)4,74(B)5,65(R)2,00 = 14,40 total, x70

Red: 2,00(R)5,95(R)5,65(B)2,00 = 15,60 total, x80

RR/2: 2,00(R)5,95(R)1,00 x10

BR/2: 1,00(B)5,65(R)2,00 x10

As above (R) and (B) are red/blue markings. I made a frame to help marking and cutting, cut from 2mm soft plastic board.

I also attached the paper model files.