HOW TO MAKE YOUR OWN GEO-DOME
I have looked on the net several times and i don't see this up anywhere, so here it is. If you have access to some nice land and are sick of plastic tents, this is a very rewarding project. Some of the following may only make sense while you're doing it.
It's simpler than it sounds!
Contents:
Intro
Materials
Preparing the poles
Making the joints
Fitting the joints
Erecting the dome
Covering the dome
This tek is a cheap and easy way to make a very strong geodesic frame that can
be covered with a variety of materials to make an almost hemispheric shelter
that is a beautiful space to be in for any purpose, and especially consciousness
expanding purposes!
If wood and canvas is used, then everything can fit in the trunk of a car and
carried to the site by one person. (a wheelbarrow may be needed if a lot of
canvas is used for a large dome. )
65 poles less than one meter and a half long each make a structure of around
5 m diameter, i.e. around 2.5m high.
The very clever but simple geometry was worked out by the genius Buckminster
Fuller in the 50's or maybe even earlier. It relies on triangles as opposed
to squares. The weight of the structure is equally distributed around the frame,
so each point is theoretically as strong as any other.
This particular tek (i don't know who came up with it, it is common knowledge
among green people in the UK) uses wooden poles and thick black plastic water
pipe sections for the joints which makes for slightly flexible corners which
makes the structure even stronger.
Looking up inside a dome covered with canvas and a parachute as an inner lining.
Close-up of how the poles are joined together. Note different diameter pipe is used to fit different thickness of poles.
-65 poles of hardwood (best is ash or hazel) or bamboo (for portable domes),
and a few spares. Strong plastic or metal tubing or rods can also be used. You
need 35 long and 30 short poles.The long poles are 11% longer than the short
poles. If you use 1m short poles you will end up with a dome of about 2m high
(i.e. about 4m across) which is not big enough to be a full-time home , but
very useable for temporary shelter, kid's space or other uses. The one i've
just made uses short poles of 1.25m (i.e. long poles of 1.39m) and is around
5m across (i.e. about 2.5m high).
Ideally the wood should be freshly cut from a coppiced patch of woodland. (Where
trees such as ash or hazel grow crowded , and are cut down from the main trunk,
they will grow back with lots of thin straight shoots that make lovely poles).
The ideal poles for maximum space have a very slight curve to them , but straight
ones may be stronger. Kinks and bents in the poles are no problem (and can look
really funky) as long as both ends line up approximately parallel to each other
. See sketch below.
Examples of suitable and unsuitable poles
Basically you need strong and flexible poles that don't branch off and that
will not snap unless you kick them really hard or jump on them . If the wood
is old it must have been kept in dry conditions . Check that it has not gone
brittle. If the bark is still on then double check for rot and worms. If the
wood is freshly cut it will be easy to remove the bark and i recommend doing
so. You can then treat the wood with linseed oil and end up with beautiful shiny
poles that will last for a very long time. But as long as the poles are always
kept dry the bark can be left on, and can look quite good, especially with hazel.
Otherwise tool handles can be used that can be bought from agricultural/gardening
shops (handles for brooms , hoes and the like) but these aren't as strong because
they lack flexibility. Avoid pine wood.
The right diameter bamboo can be used - not as strong but recommended if you're
making a portable dome. Bamboo poles must be selected with the right diameter
to snugly fit the available diameters of plastic pipe as you cannot whittle
them down (which would weaken them too much) , and neither can you put nails
or screws through them to secure the pipe ends as they can split. If you use
wood and have access to a lot of it you may be able to also choose your poles
to fit which will save you A LOT of work. ( see later about fitting the joints).
Alternatively, if you are making a small dome, thick plastic water pipe (usually
black) can be used, in which case there is no need to make separate joints.
Simply, the ends of the pipe are heated , squashed together and drilled (see
below on making the joints). But this will not make for a very strong structure
as it will be easy to accidentally bend the pipes which will then have to be
replaced. Nevertheless , strong plastic tubing should be fine for greenhouse
or temporary domes.
- A bottle of linseed oil.
- A total of 20 meters of thick plastic water pipe (usually black), in as many
different bore diameters as you can get to approximate the diameters of your
poles. This is water pipe that can take pressure. It must be thick and hard,
not easily bent. I think it's PVC pipe. If you use bamboo i recommend getting
twice as much pipe.
- 26 roofing bolts , about 10cm long, with matching wing nuts. The thread must
go all the way or almost all the way to the head of the bolt.
- At least 52 large washers for the bolts.
- A load of small nails , at least 130, about 3-4cm long.
- A cooker that you can use outside.
- A small tin can, like a baked beans can. about the size of a coke can. Aluminum
drinks cans are too thin and will not do.
- A bottle or two of the cheapest vegetable oil. stuff you wouldn't want to
eat.
- A large pot
- A good, large sharp knife for working with wood.
- A hacksaw
- A hammer
- A drill with drill bit of a diameter slightly larger than the diameter of
your bolts.
- 2 bricks or blocks of wood.
- A pair of work gloves.
The frame uses 2 different lengths of pole to create the necessary geometry.
The longer poles are 11% longer than the short ones.|
There are 35 long and 30 short poles.
And there are 26 joining points.
These are all the numbers you need. If you use 1m short poles you will end up
with a dome of about 1.8m high (i.e. about 3.6m across) which is not big enough
to be a full-time home , but very useable for temporary shelter, kid's space
or other uses. The one i've just made uses short poles of 1.25m (i.e. long poles
of 1.39m) and is around 5m across.
First cut the poles to length . 35 long and 30 short. The long poles are 11% longer than the shorts. You can afford to be inaccurate by a cm or two here and there, but not much more!
With the knife remove any protruding sharp stubs that could rip your canvas
cover. Wipe the poles with a cloth soaked in linseed oil, to help preserve the
wood. Mark one group of poles by sticking a bit of tape around each to help
you easily tell longs from shorts. This will help you later.
This is a weird and slightly messy activity but the results are worth it.
Cut your plastic pipe into 15 cm sections with the hacksaw. You need 2 for each
pole, i.e. 130.
Cut a few spares.
Set up your cooker outside ( on a day without wind if its a gas cooker) and
sit the tin can on a small ring.
Now sit a pipe section vertically upright in the tin can and fill with oil until
half of the pipe section is submerged. You will need to add oil during the work
to maintain the oil at the same level. Now turn the heat on at medium. After
10 minutes or so the oil will get hot and soon you will see that the pipe section
is starting to slowly sink as the submerged end becomes soft. As soon as this
happens remove the pipe from the tin can , place on one brick, and squash the
softened half with the other brick so as to flatten it until the two sides just
stick together. You should end up with something that looks like this:
This takes a bit of practice to get the right heat setting. Too cold and the
pipe won't get squashed enough . Too hot and it will just melt and get squashed
too much and will then be too bendy or brittle and unsuitable once it's cooled
down. You want to try to avoid flattening the pipe completely along the line
where the flattened and unflattened parts meet, so as not to create too much
of a crease there. When cold, the flattened part must be stiff and not easily
move back and forth like a flip-flop. look at the photo to see what a good joint
should look like.
If you are going to use bamboo poles, i recommend longer pipe sections (say
30cm) that are only squashed for the last 7cm or so.
Now drill a hole in the flattened part 4cm away from the end of the unflattened
part. Always measure from that end, which is effectively the end of the
pole, once fitted, and not from the other. Keeping this measurement constant
will ensure correct geometry even if the pipe sections are not all the same
length.
Now repeat this 130 times, and a few more for spares!
Fitting the joints
What needs to be done next is the most work. The pole ends need to be wedged
into the unflattened halves of the pipe sections, so that both flat ends
are on the same plane. You need a tight , snug fit of the pole ends into
the pipes. To achieve this you most likely need to whittle down the ends of
some of your poles. (if you use bamboo you can't do this as it will weaken the
poles too much. You just have to have the right diameter poles to begin with).
If a pole is nearly the right diameter but a bit on the thin side you can use
a few layers of duct tape to get a snug fit, but this is good only for making
up small differences in diameter This is where having different diameters of
pipe can save you tedious work.
The pipe ends are best fitted on after softening by immersion in boiling water.
Half fill a pot with water, add pipe sections, bring to the boil, and keep on
simmering throughout the operation. Now you can start working with your knife
to thin down the ends of the poles to fit the pipe sections on.
Use gloves.
Note that softened pipe will expand to fit poles that it wouldn't when cold,
so take care not to whittle too much . MAKE SURE THE POLE GOES ALL THE WAY IN
, to the end of the unflattened half. If a joint gets stuck halfway because
the pole end isn't whittled down enough, you have to cut it out with your knife,
whittle some more and use another one.
Fit the pipe sections so that both flat ends are on the same plane.
If there is a slight curve on a pole, fit the pipe sections so that the curve defines a plane at right angles to the plane of the flat ends; in other words when you put the pole down with the flat ends parallel to the ground the curve is sticking vertically upwards. This way when you erect the dome the curve can be vertically outwards, giving more interior space.
Now hammer a small nail through each bit of plastic pipe , into the wood , to
secure the joint in place. Hammer the nail all the way in so the head is flush
with the surface of the plastic. (Skip this step if you use bamboo, or use strong
glue).
Once all this work is done, you will be amazed at how quickly your dome can
be up!
Prepare a flat piece of ground, a circle of a diameter larger than the expected
diameter of your dome. If the ground is on a slope, don't dig in , but raise
the ground to make a terrace by adding earth and rocks as necessary , smoothen
with a rake and pack down by stomping. If in a dry environment clear the area
around the dome site to avoid trouble in case of fire. Do not erect the dome
under trees which can fall or drop branches on it in a storm. Dig a small trench
around the dome (about half a meter away) to channel water away during rainfall.
Lay your poles down on the ground in the following pattern:
You can see now where we're going! The ends of the poles do not meet because
of the different lengths. By bringing the ends together the structure becomes
a dome.
START FROM THE CENTRE. Pass the bolts through the holes of the joints using
a washer at each end. The stacking sequence is not important. Do not tighten
the wing nuts. fully. As you join the last poles of the central pentagon the
center will rise, giving you a squat 5 sided pyramid. This will be your roof.
As you keep joining poles together you will need to lift the structure from
the nearest already done joints so as to make pole ends meet. Two or more people
will make this job easy. Just make sure the long and short poles are in the
right positions, following the diagram.
Once the dome is fully erected (hoorray!) , tighten the wing nuts. and it's
ready to be covered!
You should end up with a structure like the one in the first photo.
The cheapest and most portable way to cover a dome is using heavy duty waterproof
canvas and heavy duty plastic. If portability and cost are not an issue, more
rigid solutions will be preferable. I will describe the canvas and plastic way
here as this is what i have used so far.
Stay tuned for more rigid solutions!
Marquee hire places sometimes can sell you used bits of canvas and plastic.
Buy as thick canvas as you can afford, it's worth it. The canvas is essential
for breathability. Using only plastic is cheaper but unsuitable for anything
but a greenhouse or a very temporary shelter, as condensation and poor air exchange
inside the dome will soon create problems (such as water dripping onto your
bed!).
If you or someone else can do this with their sowing machine, the cheapest way
would be to buy a roll of canvas , cut strips and sow them together (double
stitch using sowing machine) into a rectangular or square piece. The strips
need to be sown in a sort of staircase fashion with a central strip and then
subsequent strips on either side sown so that the steps created by the seams
are always going downwards. In this way, rainwater flowing down the outside
of the cover will not enter through the seams.
I use a piece of canvas which is just under 7m by 6m which covers a dome of
5m diameter very nicely. The corners are cut off so that the canvas does not
touch the ground.
Both canvas and plastic need to have eyelets fitted along their edges so that
they can be tied town.
The canvas is breathable but will rot if it touches wet ground, so it is used
to cover the dome leaving a gap at the bottom which is then closed by the plastic
. The plastic can either be sown around the edges of the canvas (double stitch
using sowing machine), wide enough strips so that the bottom will lie on the
ground enough to have big rocks placed over it, all around the dome. This keeps
the cover down when the wind kicks in.
or, better, a separate long strip of plastic sheeting is used to make a sort
of "skirt" , which is tied around the bottom half of the dome , with
the canvas thrown over it. A large overlap is necessary to avoid wind coming
in, i.e. the canvas must extend well over the skirt, nearly to the ground. (see
photo below)
The skirt is long enough so that the bottom will lie on the ground enough to
have big rocks placed over it, all around the dome. The hem of the skirt has
eyelets fitted along the edge, and is tied tightly around the frame , just above
the tops of the bottom triangles where the frame starts to angle inwards . For
a 5m diameter dome two 7m by 2m strips of plastic had rope passed through their
eyelets and tied round the dome. This way there are two points on opposite sides
of the dome, which can become doors by pulling the ends of the two strips apart
like curtains. Heavy duty velcro tape is then used along the edges to have a
sealable entry point or window. The skirt is held stretched tight by the rope
on the top and by the rocks at the bottom. A length of thick elastic cord tied
round the outside of the skirt helps keep it from flapping in he wind.
A nearly-finished low-budget dome. The white canvas cover needs a few more
eyelets along the bottom edge so it can be tied to the ground with strong pegs.
The pink line indicates the height of the dark green plastic "skirt",
where it is tightly tied around the frame using thick rope through eyelets fitted
along its top edge. Black vertical strip along the edge of the skirt is velcro.
Shade cloth stretched over the top of the dome protects canvas from intense
sunlight and reduces temperature inside the dome. Two or more openings allow
for air circulation in hot weather. In still , hot days the skirt can be removed
completely.
The canvas is then thrown over (needs two people) and tied down with strong
pegs.
Wind is the main thing to consider when covering and securing your dome. If
a strong wind enters the dome it will try to lift it up, so make sure there
are no gaps and secure everything down really well, using good high tension
cord, big heavy rocks and serious pegs. DO NOT TIE THE COVERS TO THE FRAME.
Tie everything to the ground. The covers should be stretched tight over the
frame.
In case of extreme wind speeds, strips of chicken wire fencing can be thrown
over the dome in an X fashion and held down with big heavy rocks. This should
keep the thing in place!
Heating can be achieved with a new catalytic gas heater or a wood-burning stove
if you know what you're doing. I won't go into this here as it is a fire hazard.
Additional layers of insulation can be placed between the canvas and the frame,
such as large blankets . An old silk parachute or two (army surplus shops) make
gorgeous breathable liners.
Lighting with a gas lamp or a solar electricity system and LED clusters. Avoid
candles if your dome is covered with flammable materials.
Be super careful about fire risks. Keep gas bottles and other fuels outside
and away from the dome.
Email me with any queries.
Enjoy!
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