DIY Geodesic Dome Greenhouse

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Geodesic Domes are awesome.  This Instructable will show you how I built a 20′ dome for about $250, with the majority of that cost being the greenhouse plastic ($167 with shipping.)  That’s right, the structure itself cost less than $100!  I will also write about what is wrong with this design, how it came about, what I learned from it, and what you might want to do if you’re building your own.

Buckminster Fuller wanted his dome houses to be cheap, quickly constructed, and portable.  Yes, your house was supposed to be able to be picked up with a helicopter and dropped off somewhere else!

My purpose for building domes is the same as Bucky’s:  to save humanity from extinction.  We are currently building houses the same way as we did thousands of years ago.  Bucky said we would adopt his new technologies only when it was absolutely necessary.  Well, the time has arrived.  Here is why YOU should be living in a dome:

1)  They use far less material than a square building
2)  They are much stronger, domes have withstood hurricanes and tornadoes, even a nuclear blast
3)  They use less energy, the oft quoted amount is 30% less, but it goes up as the dome gets bigger

Well, luckily for you, these problems become a blessing in disguise because I have spent the last 40 years to put together the world’s most comprehensive collection of woodworking plans.What if I told you that you could get your hands on 16,000 woodworking projects with already “done-for-you” plans with step-by-step blueprints that let you build stunning, professional woodworking projects — easily, quickly & hassle free?

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I am submitting this as part of the “Win A Home Fabricator” contest.  If I had had one when this started, it would have shaved days off of construction and lots of frustration.  My next dome will be made out of bamboo, and hopefully use home fabricated vertices (the connectors between the wooden struts.)  So if you like this Instructable, please rate it highly so I can make a better dome next time, and work toward that goal of saving humanity from itself.

Step 1: What type of dome

Picture of What type of dome
There are many choices in dome construction.  I chose to build a 3/8 3v dome to keep the complexity low.  This is where the ‘designed on a computer” part came into play.

First, I used a program called Dome Designer to play with raw material lengths.  It is very useful in calculating the amount of scrap that will be produced, and letting the user experiment with different dome frequencies and sizes.  Unfortunately, it has a tendency to stop working, and then needs to be reinstalled in order to start again.  Part way through the project, it stopped accepting my license key, and the creator never returned my emails.  I wasn’t about to spend another $100 on a program that doesn’t work, so it was back to the web.  In the end, everything I needed was online.  The scrap length didn’t matter on a dome this size anyway, so it was no loss.

The design tutorial that comes with Dome Designer was actually one of the most useful things I got out of my $100.  In it, they point out that most domes are overbuilt.  People making a house are used to using 2×12″ boards, and think that it should naturally be the same with domes.

This is not the case.  The stress that is put on dome struts is actually tension, instead of compression.  Picture a drinking straw, standing vertically.  Now put a stack of books on the straw.  It immediately bends over and drops the load, breaking if it were something like wood.  But what if you were to suspend the books from the straw?  It could hold them until the end of time.  This principle applies to domes, all of the force exerted on the struts is pulling, not squishing.

That’s why I built this dome out of 1″ (which is actually 3/4″ in the real world) sticks, weak and many cracked.  I wanted to see if they could hold up.  More on the results of that later.

These are the most useful online tools I used:

Desert Domes has a number of great resources, the Dome Calculator and Reverse Dome Calculator being my most used.  It is helpful for figuring out the length and number of struts, and number of vertices needed for different frequencies of domes.
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Then I used this diagram during assembly:

3V 3/8 Assembly Diagram

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The same pattern is repeated 5 times. The greyed out area represents the core triangle.

Bend angles for pipe or EMT geodesic domes can be rounded to the nearest degree

Bend angles for timber domes should be rounded to the nearest tenth of a degree (or 1 decimal point)

 

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3v_geodesic_color_coding_chart1-300x205For a 3V 3/8 geodesic dome you need:

30 X “A” (ends bent or cut at 10.04°)

40 X “B” (ends bent or cut at 11.64°)

50 X “C” (ends bent or cut at11.90°)

 

 

 

Strut assembly at base of the dome

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Dome frequency is basically the number of triangles that exist in the dome.  The higher the frequency, the stronger the dome, and the more complicated and more materials you will need.  The one pictured is a 3v (frequency 3) 3/8 dome.  The 3/8 means it is 3/8 of a sphere, so you can imagine just cutting the top 3/8 off a baseball, and that’s what it will look like.

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Sources: instructables

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