## Step 4: Make the Struts

First, we took the boards and ripped them to be 3/4" x 3/4" x 4'.  This took several hours with two of us, but we also did twice as much as was necessary.  Stick with 25 boards.

Next we'll need to determine strut length.  We'll work with 4' boards and you can adjust if your doing a different size dome.  Add the length of hose in the middle of the vertices, the part that doesn't have any wood in it.  If you are doing a 6" hose, and have a 2" hole bit, each end of the strut is in 2", and that leaves you with 2 inches to add to your strut length.

So our 4" strut will actually be 4' 2" with the extra empty hose.

Go to the reverse dome calculator and enter 4.166 (4' 2") and choose strut C (the longest one.)  It will give you the length of all the 3 different strut lengths, and how many of each are necessary.  Now subtract those 2" of hose to arrive at your strut lengths.

A  3.521 = 3' 6 1/4"   - 2" = 3' 4 1/4"
B 4.067 = 4' 13/16"  - 2" = 3 10 13/16"
C 4.166 = 4' 2"           -2" = 4"

As the chart says, you need 30 of A, 40 of B, and 50 of C.

The number of struts will always be the same for a 3v 3/8 dome, the only difference is length.  So if you make a smaller dome, you'll use the same number of struts, they will all just be shorter.

I chose for longest one to be 4' because that was the length of the boards I bought.  As you can see, only strut length A had very much waste, and I was able to make some of those out of boards that had ends break off while ripping them.

Make sure to clearly mark the different lengths, this will save you later!

The following could be eliminated by using home fabricated vertices that can take square struts.

Next we have to dowel off the ends of all the struts.

First use the drill press to round the ends of the struts.  Be careful, the stick will be wobbly, and the drill bit will hurt if you get yourself!

After that you have to trim of the corners that are still on the struts.  We used the chop saw in a way that is probably not recommended by the manufacturer.  If you're doing this, be careful!
Very informative. I like the way you talked about having all the &quot;fun&quot; during set up. Thank you.
Rather then tape. you could use a light nylon line and a Constrictor Knot on the rubber hose. <br> <br>http://en.wikipedia.org/wiki/Constrictor_knot <br> <br>great job fella
I'll pass this on to my brother, he was wanting to build his using some sort of lashing technique. Have you ever seen this in action on a dome? <br> <br>Thanks!
The Desert Domes site has a whole section on Bamboo Domes, put together using lashings. <br> <br>http://www.desertdomes.com/bamboo.html <br> <br>In this case a V3 dome is lashed using only two sets of 4 point vertices. Since all of your struts are components of your vertices, set up and construction consists entirely of preparing vertices and lashing those together to form struts already in place in your completed structure. <br> <br>The whole design and measurement system is set up to build from the top down, as opposed to a bottom-up construction, making it easier to place and attach your covering as you construct your dome.
That's exactly what my brother is doing, although he hasn't made much progress this summer. I helped him lash the first few together, and it was actually really easy and fast.
... and i quote; &quot;... Zip Ties are a wonderful thing. :)&quot;
I guess you don't get wind where your dome is!<br> <br> It should be anchored to the ground with either 3 foot long 2 x 2 stakes or rebar hooks or it will blow away.<br> <br> Tape is never going to be a satisfactory solution to securing a structure.<br> <br> Glue the rubber pipe onto the wood or put a small screw through the pipe on each - Amazingly a normal hand screw driver works just as well as the electric ones.<br> <br> see <a href="https://www.instructables.com/id/Geodetic-greenhouse-low-cost/" rel="nofollow">https://www.instructables.com/id/Geodetic-greenhouse-low-cost/</a>
Thanks for the comment. I've already replaced the tape with screws, it wouldn't have taken so long but my drill was on vacation. <br> <br>I have been considering the anchors. I'd like to make them removable, as it's a portable structure. You'll notice it's in two different spots in the pictures. It does get quite windy here, so I must prepare!
you can get &quot; dog leashes&quot; earth screws for cheap at china mart or pet store, this would hold your dome down.
Buck Minster Fuller himself noted that a large enough dome, one half mile by his estimate, would create enough heat on the interior via solar energy, to lift the entire structure off the ground, similar to a hot air balloon. <br> <br>For a simplistic, inexpensive, and rapidly mobile anchoring system, try attaching one gallon plastic bottles full of water to each of the vertices once removed from the ground, around the perimeter of your dome. Each of the bottles would weigh 8 to 9 pounds (1 gallon distilled water equals 8.4 pounds) and with enough string could hang one to 2 inches off the ground, providing an extra 120 pounds of Anchorage to your structure.
Yes, two or three iterations from now, mine will fly! Muahahahahhahahh!
I like that greenhouse! I have the same problem with the joints, they are a little floppy. When it's all together, they hold very well, but with a load pushing directly down on them, it inverts the hexagon or pentagon. This happens because neighboring vertices all slip and fudge around enough to give the one I'm pushing on enough room to flip inward. A backing, as in the instructable you linked to, may be able to take care of that.
Nice work. I built a 28' diameter 4/8 dome in 1975, using 2&quot; x 2&quot; stock. I milled the stock with an Alaskan brand chain saw mill from a Douglas fir log about 18&quot; in diameter. Made all of the vertices from 3/4 plywood which I got as scrap from a cabinet makers shop. Cutting them was tedious with a hand saw, then clipped the tips off to leave a 1.5 inch flat normal to the strut vectors. Each strut was cut for half-lap joints on the ends, and then wood screwed to the plywood vertices. My only power tool was the chain saw. Building the dome frame cost about \$10, mostly in chain saw fuel and wood screws. <br> <br>I wanted a durable, cheap, insulated covering, so I covered it with the cheapest thing I could find - a surplus Army parachute, stapled to every strut with furring strips. Then I used a commercial spray rig (my Dad's company owned it) to cover it with about an inch of spay on foam insulation, covered that with 3/4&quot; mesh chicken wire, then another inch of foam. Let that cure a week, then painted it with asphalt mobile home roofing compound. It is still standing, on my brothers property, which frequently gets 18&quot; or more of snow in winter.
Wow that sounds like you're hitting a lot of the things I was hoping for on the next episode. How much did you spend on the chicken wire? Did you Dad say how much the foam would have cost if it wasn't in the family? Was it closed cell or open cell foam? How is the inside temperature during the winter? From my research the spray on foam seems like one of the quickest ways to take a dome from frame to complete. <br> <br>Thanks! <br> <br>
It was a long time ago, but as I recall the chicken wire was \$18 for an 8' by 100' roll. I bought three rolls, so \$54. If you know what &quot;hog rings&quot; are as used in upholstery, then you'll understand when I tell you that I used those to edge join the sections of chicken wire. The foam was closed cell polyurethane foam. My Dad owned the spray gun and mixer, I bought one barrel of each liquid component through his company, and spent \$84 on them. I really don't remember the cost of the two 5 gallon buckets of asphalt roofing paint, or the rollers - it was pretty cheap. <br> <br>My brother repaints the dome every 5 years or so, and he also sprayed the interior with Kilz epoxy sealant paint, and installed two bi-metallic coil thermostatically opening vents at the peak - those are still available, made for greenhouses. It is quire warm inside, even when buried under snow. He has a &quot;dairy barn&quot; type small electric heater in it. <br> <br>I actually built 5 domes, in total, but only the one geodesic. The rest were experiments, and two of them failed pretty quickly. The other two stood up quite well, and one of them is still being used as originally installed - as the roof of a hay storage/stable which is 24' in diameter. We set that one on a frame that lifted the lower edge of the hemishere 8' feet in the air, while leaving the opposite edge 4&quot; off the ground on framing.
This one has actually failed now. I am going to post some pictures, and a write up, shortly. It wasn't the dome, or the materials fault, it was operator misuse. I picked it up (with two other guys,) and we moved it onto a slope, so I could use it to keep cows out of a garden area. The slope caused breakage, and a very long, slow process of destruction. I let it happen in order to see the results, and I'll post it as soon as my camera is rounded up.
I tried this in 1970. Blew away in the first high wind. Nothing of value could be salvaged. Hope you have better luck .
Yes, I still haven't figured out a good, movable tie down system. If I've got it attached well enough to not blow away, the way I think it might get destroyed is just by being flattened. We'll see! Thanks!
I had a thought. what about the tent weights used for art fair tents? assuming the structure can support that much weight, but it would not have to be very much per &quot;leg.&quot; http://keletica.com/keletica-dialectic/44-howto/70-weighty-subject.html
That would probably work very well.
So here is a question from someone with very little geo-dome experience, just this 'bile and some observations... <br> <br>At our local playground is a geo-dome play structure (old school style). what they did was take metal pipe and pinch the ends flat and put a bolt through the connections. ( they &quot;finished&quot; it with a large 4' washer on the outside). <br> <br>So why could you not just do the same thing with PVC? That is , heat the ends, pinch them in a vice and drill a hole. The only hitch would be the &quot;length&quot; in the dome calculator would be the distance between the holes. This can be done with a simple jig. this would address the rigidity issue, and simplify construction. <br> <br>Any thoughts?
I've had some friends back here that have been asking about PVC as well. I preer to avoid it because I've heard it's pretty toxic. Even if it isn't, when it breaks, then I've got a million little shards that are going to be laying around forever. But if one were to use it, a friends suggested that you could heat it up in order to bend the connectors to the required angles (which I believe are listed a couple comments below. <br> <br>The galvanized steel would make a super strong dome, but I didn't want to spend the money on it. My neighbor has some that we will be using to build him a dome though, so stand by for an instructable on that. <br> <br>Thanks for writing!
The ones that bent were, I think, 1-inch electrical conduit. Whatever that was in 1970, probably steel.
Electrical conduit makes some seriously strong domes. If I had a bunch extra of it sitting around, I'd use it. My next one will be with 2&quot; x 6&quot; 's, because it's going to be ginormous, and I have a lumber yard right up the road.
Not sure about PVC, but there have been people who have used galvanized electrical conduit. PVC seems to get a bit brittle over the years when exposed continuously to UV.
PVC isn't UV or temperature stable- 3 months in direct sun and it starts to disentergrate- CPVC (the grey kind) is better, but more expensive and more flexible- <br> <br>I built a lot of crazy stuff with PVC (google Sam's Nascar simulator) but nothing that will get a lot of sun---
I built one like this a few years ago using PVC pipe, black rubber hoses from some old washing machines and some cable ties (zip ties). The plastic cable ties work great for securing the struts to the hose connectors. Great job! <br />
Thanks! Zip ties are a wonderful thing :)
Yay! Ron Paul! ;-) <br> <br>(re: Ron Paul bumper sticker in pic.) <br>
Yeah, nice sticker! This one gets a vote-up for general intelligence! ;o)
Great, you must be believers in Liberty and the Bill of Rights!
Indeed sir! (and a dome-o-phile)
Pretty scary rounding the ends of the struts... Have you ever seen rotary tenon cutters like this? <br> <br>http://www.rockler.com/product.cfm?page=11459&amp;rrt=1
Yes, I did get bit once. Those cutters looks pretty great., but it's kind of expensive. At that price you're already a quarter of the way to a home fabricator, and printing out the vertices yourself. <br> <br>http://www.makergear.com/products/3d-printers <br> <br>Thanks for the comment!
I wanted to get one of those tenon cutters myself but the price of the cutter would've been more than all of the other materials put together. My solution: a 1 inch diameter hole saw with a 1/16th inch blade thickness. My vertices are simply six-inch round stock, sliced 1-1/2 inch thick, and drilled with a 7/8th inch speed boring bit. <br> <br>I use a hack saw with a carbide grit bar blade to cut away excess material from around the tenon, in a hex pattern. <br> <br>Total cost for the hole saw, speed boring bit, and hacksaw bar blade, about eight dollars.
Great job! I've always meant to build one. maybe this will get me started. seems like if you used pvc pipe that just fit into the hose, it would be a pretty quick job although a bit more money than scrap wood. <br>I was wondering if you could start assembly at the top. Ie build the top pentagon and then lift one side and add the next row etc.
Buckminster built a lot, if not all of his domes from the top down. They used some sort of jack or crane, like they use in grain elevator construction, and just had a crew of guys attaching a row, then jack it up one level, attach another row, etc. He built huge domes, 200' across, in a couple days using this method! I'm definitely in the market. <br> <br>I still don't like PVC too much, mainly because it's a permanent plastic, so we're going to try bamboo next. We've already got 6' pieces, which means if we built the exact same dome, it would be 28' across instead.
Thank you for the tips. After reading your Instructions I believe I could build this type of green house also. You got a vote from me. Thanks again.
Thank you! I'd love to know how it works out.
If anyone is interested the author mentioned duct tape not working to good. I'd like to recommend Permacel Pipe Wrap tape. I've stopped using duct tape when I really want something tough as nails. The strength and adhesion of this stuff is extraordinary, you can barely peel it off the roll. In the 6&quot; wide it helps to have two people unwinding it. I've never seen anyone tear it and you need a sharp blade to cut it. And it isn't coming off. It is thicker then any tape I've ever tried. <br> <br>No I don't represent the company. Oh and it isn't cheap.
Hmmm... I'd be interested to know if that would have permanently secured it. The other reason I'm losing the tape, though, is that it too SO MUCH TIME wrapping every connection. Cutting that part out of the labor will cut a day or more out of total time to completion. <br> <br>Thanks for the advice though, now I know where to go when I need super tape!
Great job. Even if it blows to China you will still have learned enough to make it worth while. I've been wanting a greenhouse/auxiliary structure. Something like this would be excellent.
Exactly what I was thinking, plus I really wanted to see what the 3/4&quot; struts could handle. Thanks for commenting!
Wow, what a lot of comments! Thanks all!
The third point of a triangle, Washington.
Looks very weak and flimsy! I would not count on it being around too long. You put a lot of good hard work into it though! Too bad, it will not be reliable, maybe as a short term green house cold frame! Beeen there &amp; done that! Thanks for the tips on constructing it! A frame style is much stronger and will last many more years. FYI
Thanks for the comment. I suspended a Topsy Turvy 1/2 full of dirt from one screw last night, with no problems. <br> <br>One reason for building this out of 1x1's is to SEE if it's really weak and flimsy. Conventional, square 2000 B.C. construction requires that we build everything out of 2x12's, 4x4's, and larger. Unfortunately, that approach is exactly opposite what is needed with domes, as the less flexible the structure, the more prone to breakage. That's what I'm testing out, how low can we go? <br> <br>I'm interested in your results from your been there done that? What size struts were you using? Were they breaking? Did you have a snow load and failure? <br> <br>Our next test is out of bamboo, but this one is really important because if 1x1's can withstand the wind here, then we're golden. If not, from my impression of the strength I currently have, 2x2's will be invincible.
No idea what a Topsy Turvy is! I am guessing it is some sort of flower pot?! Yes I have snow loads that vary from year to year. Many fails. Still looking for a strong system to store my stuff without spending a lot of money. Cold frames and multiple yard tools, extra firewood and other toys are my main concerns ! Thanks for replying so fast!
Lots of good tips and a awesome dome! :D