My geodome greenhouse project

  • I have always wanted to build a greenhouse and I think this year I have to get it done to save my plants. I have a lot of lettuce, cucumber, squashes and other veggies that we planted in July. It looks like they are not going to make it outside, so I have the perfect excuse. ;)


    I have almost no money for this project, so I have been looking at ways of sourcing material for cheap or free. Recently I got around 200 posts for free from a friend, I think they could work well as struts. They are just over 2" thick and 7feet tall. If I cut the sharp end off of them, I will be left with 80 inches, which is probably the maximum length I can get out of these.

    21364763199_262eb32963_z.jpg 21540489502_500efb8966_z.jpg

    I am thinking to build something around 30’ or so in diameter. Looking at this geodome calculator I would have enough material to build a 3V dome with a diameter of 32 feet. Here are the results list of parts from the calculator:

    Strut 'A' length : 5.58
    Strut 'B' length : 6.46
    Strut 'C' length : 6.60
    Diameter : 32.00
    Surface area : 1608.45
    Floor area : 791.04
    Circumference : 98.88
    30 lengths of 'A' size struts
    40 lengths of 'B' size struts
    50 lengths of 'C' size struts
    6 five way hubs
    25 six way hubs
    15 four way hubs - around the base of the dome.

    The real challenge is finding a way to build the hubs. Most of the strut and hub designs I have seen using 2x4. I am looking for a cheap but reliable way to build the hubs, but I have not found any design that would really stand out for me. The zip tie hubs seem like they could work in this case, here is an example with PVC pipes:


    Seem like they would work if I use a heavy duty zip-tie or strips of metal to build it. However still it seems overly complicated. Does anyone have suggestion for how I could build the hubs?

  • This project would work. It shows using 2x4’s but the braces are hand made of steel. It would work just as well with posts. I would then reinforce the corners with hemp rope to give it that pioneer look.

  • Could you slit the end of the post with a skill saw?. Weld a hub out of 2 x .125 bar stock ?

  • Have you seen Funvill’s pocket universe?

    It uses these chicken coop brackets which hold 2x4s.

  • Google images for wooden tinker toy set and see if you are inspired. Find a log with the desired diameter and cut slices thick enough to then bore holes. Search Lee Valley for Veritas® Tapered Tenon Joinery System.

  • The tapered tenon is sweet… But Lee Valley if a cruel place to send someone who is inclined towards tools and does not want to spend a lot of money… I speak from experience here.

  • Thanks for all the tips so far! Yes price is definitely a big factor. I am trying to find a solution that would cost less than 4$ per hub.

    I saw these eye screws at surplus the other day. I wonder if I could attach those to each end of the posts and connect them with stainless zip ties.

    eye scew.jpg

    Do you think that would hold up?

  • Linux

    I know so little about this it’s not even funny, but I do know that there are some tenon cutters in the garage here. no idea if they’d help you, or if i could borrow them, but i can find out?

    Learning and working on learning more!


  • making a jig to turn out round tennons would not be difficult.

  • I think the trick is getting the angles right. It’s not like making spokes on a wheel, they are on different planes as well

  • Linux

    What about laminated plywood hubs?
    Could you not use the CNC router at the hack space to get a really accurate/precise cutting pattern for each of the layers of a laminated hub?

    I am pretty sure we have the mortise/tenon set that would work on those posts if you want to borrow them.

  • What about laminated plywood hubs?

    I think that is my best bet right now considering the tools and material I have access to. I actually have around 5 sheets of 1/2" plywood at home as well that I could use for this project. I’ll design something in onshape and report back.

    I am pretty sure we have the mortise/tenon set

    @Chris I may have to take you up on that offer!

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