Geodesic Dome Greenhouse – Part 3 – Strut Construction


Hello Everyone,
This is the third video in the series about building a geodesic dome greenhouse. This
time I will cover how to build the interconnecting struts which are made from red cedar. I choose
red cedar because it is rot resistant. You could use treated lumber, which is substantially
cheaper, but I was concerned about chemicals leaching into the water for my aquaponic system. The site I used for the calculations is acidome.ru.
The entire site is in Russian, but Google Translate does a fairly good job converting
the text. The calculator lets you enter the diameter of the dome, choose the hub type
and size, and even the dimensions of the struts. It will then calculate the angles needed at
each hub and also calculate all the various sized struts and labels them with the dimensions
taking into consideration the size of the hubs. The best feature is the ability to have the
software calculate a flat base, since a 3V 3/8th dome is not flat. One click and the
struts are recalculated with the proper lengths! With a 33 foot diameter 3V dome, each triangle
will never be wider than 6 feet. This will allow me to purchase the polycarbonate glazing
in 6 by 24 foot sheets, helping to minimize the amount of scrap. The struts are made from red cedar 2×4’s
by 14 feet. This will be enough material to cut 2 struts from each board with some scrap.
The end of each board is cut at a 12 degree angle so it will align with the hub. Not every
hub connection is exactly 12 degrees, but there is enough flex in the structure for
the angles to average out properly. Once the struts are cut to length, they are
run through the table saw to add a slight bevel to them. When the dome is fully assembled,
the polycarbonate panels will rest fairly flat along the bevel. This will also insure
that the height of each strut is the same since it can vary slightly from the mill. Next I remove some of the material from the
end of each strut using a dado blade mounted in the radial-arm saw. This space will provide
an area for the top tab of the hub to rest and provide enough clearance for the polycarbonate
panels over the crown of the carriage bolt. I built a jig to act as a stop and keep each
strut aligned properly during drilling. This allows for a consistently placed hole to be
drilled near the end of each strut. The placement of this hole is important so it will fit properly
into the hub and provided an accurate length for the hub and strut combination. And now, the perfect excuse to use one of
my favorite tools! The bottom of the head of a carriage bolt
has a square neck so it can grab into wood to prevent it from turning. To get it to fit
into the metal tab, I would either have to drill the tab’s hole larger, compromising
some of its strength, or turn down the neck of the bolt in the metal lathe. I chose to
turn each bolt and then will re-galvanize the area with cold-galvanizing paint. Here is an example of how the final assembly
will fit together. The strut is sandwiched between the two hub tabs and then tightened
into place using a lock washer and nut. This top view displays how each strut can
pivot slightly on each hub. Since the angles of each triangle section aren’t the same
from one section to the next, this allowed for me to make the same hub and allow the
pivot against the bolt to make minor changes to the angles. This side profile shows how the dado in the
strut allows the polycarbonate glazing to clear the area without hitting the tab or
bolt head. Finally, this profile displays how the glazing
will set flat into the beveled area that is cut along the top of each strut. I assembled the base to verify that the calculations
were correct and the pieces fit together. So far, so good! That’s all for now. The next video I plan
on detailing some of the site work. Thanks for watching!

85 Replies to “Geodesic Dome Greenhouse – Part 3 – Strut Construction”

  1. Great update man. Can't wait to see it all done. How long do you think this big project will take you to finish?

  2. Hi, Great video. Looking forward to seeing its completion. The BigelowBrook domain doesn't seem to be working though.

  3. The BigelowBrook domain is working now….I think we had a small outage. Thanks for letting me know.

  4. @iyuriy3 Hubs like this are very labor intensive and expensive to build. I would guess they would be around $100 each to build!!! You would need 45 of them for a 3V dome! Sorry, I'm not in the business to make them. You could try the folks at growingdome com and see if they sell hubs. I know they sell complete domes.

  5. That lathe looked like it was just as happy to be used as you were to use it. It munched that square bit off like it was made of chocolate.

  6. This is a great video!!! I'm having series equiptment envy! Thanks so much for the info for angles and the website calculator. I can't wait to see how you put on the panels. Are you going to put in some motorized temperature controlled vents similar to what you did with your other greenhouse?
    Are you going to use this greenhouse just for aquaponics? If so, do you have a floorplan yet for how your are going to set up your system?

  7. @BlueCherryFae It's primary use will be for aquaponics and testing some of the automated controllers that we design. There is a floor plan in the first video of the series around the 2:00 minute mark. I'm glad you're enjoying the videos. It's fun to share the info!

  8. @BlueCherryFae Sorry my english, i am developer dome-calculator been showed in video. Welcome to calculator page acidome.ru/lab/calc/ and be happy.
    Coming soon: new connection type "Cone" without connectors.

  9. @web4deb Hello, why you show my calculator tool in video and don't show link? Please, public this link in video description: h t t p://acidome.ru/lab/calc/
    I am fan "without metal connectors" connections type.
    Thanks for use, russian JS-developer.

  10. @popitch64 I'm sorry, I forgot to add it. It's in the description box now. Keep up the good work!

  11. i wonder if it would be a good idea (and maybe help keep the cost down) to use a different material for the lower triangle segments. like plywood with vinyl siding. after all, the sunshine shines down from above

  12. @dwiggs77 Maybe in the south you could do it, but up here in the north the winter sun is VERY low.

  13. Outstanding series! I plan to start building a geo-greenhouse for aquaponics this fall and this looks to be exactly what I had in mind so far. Started on a chicken tractor this week and hopefully by this time next year everything will be up an running smoothly!

  14. I really appreciate all the work you are putting into this project and commend you for putting up on here for other to use as well. I was wondering what type of fish are you planning in your aquaponics system? I live in Michigan and have been planning on doing something along this line as well and really like your design for the geodome greenhouse. I have been thing Tilapia and Catfish, but have also considered Crayfish. Any thoughts will be appreciated. Mark

  15. @emrcon Thank you. I enjoy doing the videos and hope people can use them for ideas for their systems! Here in CT it gets cold too. Since I don't want to keep my water above 75 for the Tilapia (which I can barely get to that during the summer), I just grow goldfish in my small greenhouse. When I finish this GH, I'm planning on goldfish, koi, and trout. I may do some other native fish to the area like perch or bass. I'm not too sure yet. I may throw in the crayfish from the stream too.

  16. @therawlifefamily I meant for resale. IE: If I were to want to replicate your structure, those jigs you made would allow me to do that.

  17. @therawlifefamily The cedar alone is about $2K. The total cost of the structure and site work will be around $15k

  18. Lovely videos man! I subscribed right away!

    I'm in the process of building my own dome and your video was actually a suggestion from youtube when I had viewed my own first dome video.

    I'm so happy I saw your video now, as I now manage to do a flat base on my 3/8 3V dome thanks to that Russian calculator 😉

    I'm very impressed by your work, amount of space, tools, etc… Definitely looking forward to more videos of your progress!

  19. @popitch64 Hello, thank you for such a great web page.

    I have one question. In the section for the triangles, you list this:

    1. 45 pcs. L412-R235-L412-R235-L404-R240

    I know that L is the length of the sides of the triangle. What is the R?

  20. @AulusCordus there's 3.5" between the blade and fence. Plenty of room for fingers! I got the carriage bolts for free…..it's worth a couple of hours on the lathe to turn them down.

  21. hi man, you totally inspired me to make i geo dome with aqua ponics. i watched your vids lots of times and other and did research. so now ive got my own 2v dome raised on 250mm stilts under base hubs, 4.3m dia.i got 100 silver perch fingerlings in ther and a few others ( trout, cod muscles and 100 shrimp) and 5 commets. struts are losp (organicly treated pine) 105mm washers as hubs (2 per hub) and covered in builders plastic. triangular door. LED down lights and 12V dc backup pump. video soon

  22. tried to do a vid responce but i dont know if it worked, so check my channel watch the dome vid, peace…

  23. @proder2007
    I use 14 vents in the kneewall for 360 degree low level intake including the door. To maximise the chimney effect use the entire top pentagon for the high level vent. Reinforce the pentagon and the opening, hinge it on one side and use hydraulic rams to open it. Don`t forget to install safety chains in case it ever gets loose.

  24. @web4deb I saw that after I asked the question, sorry. Can't wait to se the next video on how this is coming a long.

  25. @seventhsensestudios It may be possible but I don't have the kind of equipment to bend steel that's 1/4" thick. It took about a day to weld everything so it wasn't too bad.

  26. Hey Rob, I truly enjoy all of your videos, they are very informative and very well spoken. Keep em coming. Thanks.

  27. I'm experimenting with the Russian website and I'm not sure what the section is that's labeled: "Material of edges (bar) Width, mm ____ Thickness, mm ____"
    Also, how did you calculate the angles of the straps welded onto the 3" steel pipe sections? (If you can't tell me I might have to do some thinking and that would hurt my head).

  28. @zliminator for a 3V dome, it has 15 sides so I just averaged 360 degrees divided by 15, which is 24 degrees at each angle. If you look at each area, the angles will change a bit but there's enough flex in the steel and wood where a degree plus or minus doesn't make a difference. I ignored all the thickness and based all the calculations on the outer "skin".

  29. @yogabill You're welcome to drop by any time! FYI: Even though the shed has a smaller foot print, it cost more and took longer to build than the dome! I should have either built a larger dome and gone up to a 4V, or did a second northern dome and covered it like a shed. 😉

  30. I finally went to acidome.ru! The site is amazing, very well worked out and friendly-interactive. What was your final decision process like, on 3V vs. 4V? Cost of the extra cedar for more/shorter struts? Looks like the extra hubs would have taken only another day…

  31. @bayoufilter It was based on minimizing the scraps from the polycarb panels since they are the most expensive component. These panels are 6' wide, so with a 3v, 32.5 foot dome, the maximum triangle size from tip to base was just shy of 6'. If you go up to a 4V, I'm sure you could do a much larger building!

  32. Thank you so much for the link to that russian program! I helped me so much, understanding the pricipals! And you videos give so much insight! I just came up with an idea that works wiith poles as hubs instead of your metal hubs – which are ingenious indeed!

  33. This probably a dumb question but…how did you securely tighten the nuts on the hub bolts since you lathed off the square portion of the bolt that would normally keep it from turning?

  34. @mobiusII actually, a very good question! There's basically enough friction in the wood and (poor) alignment between the wood and the hubs that the bolts held in place. Once the heads started to grab into the epoxy on the hubs, there was enough friction to tighten them. I think there were only 2 that spun and I just used some vice grips to hold the heads. 😉

  35. What was the final diameter of your dome? I calculated a 3V dome on acidome with a 5m radius, are your struts around 2m in length? The website shows the lengths in millimeters right?

  36. Ok thanks heaps! Right now i'm doing a model in Autodesk inventor, the hubs are pretty difficult, there are angles at the end of each strut right? around 78 degrees which is why the hubs are also angled in? haha sorry for asking so many questions!

  37. The angles are roughly 78 degrees but do change slightly. For mine, there's enough slop in the hubs and wood so I made everything the 78 degrees. Because they aren't all the same angle, I spent little time trying to model this in 3d…especially since the building official didn't need it! I found an autocad script that could make a dome. private message me your email address and I'll set it to you….but, it can't do a flat base for the 3V dome…

  38. how did you make the base of the dome flat? I know that 3V domes do not have a flat bottom. I am in the process of getting my foundation laid for a 22 foot dome and I am debating on 2V or 3v but I am leary of the base not being flat. Any wisdom on this would be appreciated.

  39. Bravo Dude! However, this is not for the average DIYer. Your skill level is professional! How many of us can mig weld?

  40. the site to determine angles and such is very confusing. the websitr has changed since you used it. please help me and respond. this project is for my school.

  41. Again, great. But totally out of reach for most people. In order to make this, one needs a fully equipped wood and metal workshop which just isn't realistic.

  42. if you are having problems with strut lengths etc, do a google for 'Dome calculations'. More than enough sites out there that have calculators. Will give you all lengths, hubs etc..

  43. you dont have to mig weld, or have a metal lathe. There are numerous designs for hub connectors. All depends on your budget, skill level. Get quotes, outsource, find a retiree with a welder or a drill. Use a simpler hub design. Bolt angle brackets to a piece of pipe and bend to right angle. Use your imagination and think outside the box.

  44. At 02.00 minutes of video are do a cut on the outside of the ribs and then to will put a cover on the triangle. What is that angle in "V" of this cut?

  45. The base of the dome has 15 sides. 360 degrees / 15 = 24 degrees for each angle. The saw blade is set to 12 degrees, Technically each angle is a bit different, but for this, 12 degrees will do just fine.

  46. Hey! Could you please tell us what size the bolt is? I'm building a 2v dome with boards of 36x73mm. Was thinking of a 10mm hole as I found those stainless steel bolts at an offer! U think the wood will suffer. Using normal construction eco-preserved wood(if u could say it like that in english)

  47. I believe someone else commented to the same effect, but having managed to victimize myself with a table saw, I'll echo the thought. Watching you push lumber at an open blade with your fingers makes me cringe. Please, in the name of all things holy, install a proper safety guard and get yourself some push sticks. Beyond that, I'm on my 3rd view through on your video series, your dome seems well designed, well built, and the videos are pretty inspiring. Keep up the great work.

  48. Thought you might like to know that acidome.ru now has its own translations without needing to go to a translation page.

  49. Cool video, It's sad,that living in Russia, I can't afford such equipement as your one. I think that 3-rd frequency is most effective for construction such a buildings too, also I saw the link you are used, but do you know that for the 3-rd frequency, there is much more better way to make flat base, that allow you to recalculate stuts with only four equal lenghts, five instead. It called fuller-kruschke method : http://www.gardendome.com/kruschke/kruschke_dome.html , You could easily draw it using sketchup for example, and I think that for construction of such dimensions it would be much more easier to buld it without steel connectors – It would has made the construction cheaper and lighter, and has gave you independece of some of equipement. I wish I could have such a garage with such equipement. =) Good luck

  50. Лови лайчелу братан!) На сайте появилась английская версия 😉

  51. Jolly good work, starting from a very clever idea.
    Q1: why not use aluminium for the struts? Or for the cylindrical hub?
    Q2: you are not planning to use an opening right on the center of the dome, are you? This would be ideal to release hot air in summer days, so how will you do it?

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