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Geodesic Dome Diarywritten by Rene K. Mueller, Copyright (c) 2007, last updated Tue, November 4, 2008 The DiaryAs I proceed I will update the diary. Most up-to-date entry at top, first and oldest entry at the bottom respectively last page. 7. 4. 2008: Other Connector Ideas
At Bamboocraft.net Discussing with a friend of mine, who is a locksmith, brought up this design as the illustration shows, using a special foaming glue.
The glue, named "Fermacell 59010", is slightly foaming or expanding and seals the 1-2mm gap seamlessly - as a few tests have shown:
One bamboo I cleared using a cutter to remove the glue and see small bubbles, whereas the other the overflowing glue remained as comparison. For the first tests we dented the steel pipe, and in one case too much where you see the bamboo split - which should be avoided.
6. 5. 2007: New Connector Ideas
One idea is to use two kinds of metal tubes like electric conduits of 8mm and 10mm diameter, and either drill 8 and 10mm holes into the bamboo, and glue it into and stabilize it with a screw. For the few struts with less than 10mm using the 10mm conduit and move it over the bamboo. And then squeezing the end of the conduit and drill the 4mm hole for connecting the struts then. Will make a test of an A/B-pentagon to see who long the conduit requires to be, and also measure all struts diameter to see how much material of 8 / 10mm conduits I require. Update 2008/04/07: to use the pipe within the bamboo poses a slight risk of breaking the bamboo, as the inside of the bamboo is soft and rather weak: you can break the bamboo easier from within than from the outside; so it rather suitable to use the pipe surrounding the bamboo instead. 1. 5. 2007: Dome Taken Down AgainI stayed two nights in the dome, actually a wonderful experience with so much space, the spherical space makes an alike sacred impression as the tipi does, an cathedral like awe I've got. I gonna miss the dome, and will work for a stiffer but still lightweight solution using bamboo - as I like to avoid steel pipes which would make the frame too heavy and too hard to pitch up without additional tools, not to mention the inability to lift it up and move around when erected. The dome I took down by just unscrewing 5 or 6 connectors, and took it away like a collar, and folded it in itself as far possible - and later unscrewed all connectors on the side.
29. 4. 2007: Weak ConnectorsWith the current setup with soft-pipe as connectors the skeleton is too weak, and the sun heat softens the pipe further - so much that tying the rain cover to the ground pushes the top down - so I likely will take the dome down much sooner. I definitely require to find a better connector for the bamboo, the softpipe might only work with smaller domes and average temperatures. Things learned with this test pitch-up:
Update 2007/12/14:
CONBAM.de 28. 4. 2007: Yurt Taken Down & Dome Put on the Floor
Errecting Dome It took me a couple of days to erect the dome, usually it's a matter of an afternoon (4-5 hours) but it was so hot the last days I worked only early morning and evening before sunset. We had also some rain, which wasn't so good for the fully exposed skeleton - anyway.
I also use a skylight frame so I could reuse the skylight from the yurt. Finally, before I actually decided to switch I put over the rain cover of the yurt on the dome.
It took 4 people to move the skeleton as the base tended to fold inside, and 3 people might have worked too with some skills but finally with 4 people we did it. The skeleton itself is rather light, apprx. 40kg I think total. Once we had it over the existing floor and interior and moved it over the shelves, I had to move some interior further into the center, 10-20cm apprx., due the spherical walls. Interior Cover & Rain Cover Since I use the yurt covers (interior & rain) I had to use a cord which I tied on the height of 1.50m apprx. which is also the center of the A-pentagon - on that cord I tied the interior cotton, as first layer from outside. As next I added the yurt rain wall, also tied on the same cord - and finally put on the roof interior cotton, and then the roof rain cover from the yurt. Skeleton The skeleton with bamboo is strong, yet, the soft pipe junction are weak and soft, too soft. I don't expect it withhold a storm and make a tend (push a junction inside). The cable binders aren't that strong either, and while moving one teared apart, so I might have to use 2nd cable binder for all endings, at least on the west side where storms usually come from. I was aware that the bamboo/soft-pipe combo was only suitable for a lightweight setup, rain cover and cotton interior I reused from the yurt setup, and now realize I won't able to add another layer unless I would choose another strut endings other than soft pipe. The reason I use soft pipe was I could use them to various diameter as the bamboo came, 15-18mm - so I'm looking for other options. Anyway, I'm expecting to stay a couple of weeks inside the dome, but as far I can see won't last longer and then switch back the yurt. The next things to do:
25. 4. 2007: Raising the Dome AgainSo, finally again raising the dome, and checking if I can use part of the yurt setup, such as a skylight (octagon and a bit smaller than the top 'A'-pentagon) and this allows me as a first step to reuse the inner cotton cover (roof & wall) as well rain cover (roof & wall) of the yurt. If all does well, I will switch the yurt for the dome sometime this weekend. I noticed moving the dome is problematic due the base not being stable when it's not pushed on the ground, it bends inside and the entire dome looses its form - so I will stiffen the bottom connectors so the circular base is kept in shape so 3 person can lift it to the existing floor where my yurt sits on now. 11. 4. 2007: Coating Struts
I'm also about to finalize the connector reinforcement construction and updated the previous illustration with the new design. Next days I will make a few tests with the construction, and if the weather allows it raise the dome within the next week.
18. 3. 2007: Planning Extending/Reinforcing Connector
The wooden star would be composed by:
Since the struts are slightly bent, apprx. 8-9°, I leave 2mm as spacing, but final length of the spike will be measured on the erected dome again. Total 91 connectors, where as the bottom 20 connectors (4-way) I wouldn't enforce:
Total requirement of wood:
So, this is the plan for reinforcing the LDPE connector so far, I will of course think it over again and make small tests, e.g. the 8mm spike is small and some will enter the hollow bamboo, so maybe a small ending of larger diameter is required. The connector could be also stronger if I wouldn't have left 27.5mm but less, maybe 15mm could work too, or a whole pipe not a half but this would require a single diameter strut and with bamboo this is not possible - so it's likely worth to reinforce and find a strong connector solution in order to build the skeleton with lightweight but strong and rather cheap priced bamboo sticks. 17. 3. 2007: Taking the Dome Down Again
But before that I measured the dome:
16. 3. 2007: Raising the Dome Skeleton
Pitching the Skeleton I decided to build top to bottom, means, level by level until the bottom is reached - since the entire skeleton is apprx. 40kg it was easy to lift it for the last bottom level.
The construction map on the right helped me to lay out the struts on the ground and level by level attach them and screw them together.
Roger helped me and it took us about 4 hours.
Some Impressions
11. 3. 2007: New Way for 4V Dome
After working a lot on geodesic polyhedra the last two or even three weeks, and finding out why my L3 variant of the Icosahedron didn't provide the same strut lengths as those from B. Fuller (via DesertDomes.com
I summed up 1/1000th or 0.1% variance of length to the same strut, so I ended up with 5 strut lengths, the 4V could also have 5 strut as two strut lengths are so close but not as close as the L3. But the variance difference is quite obvious and it would mean to have more alike triangles and probably also less waste (which I have to proof first). Anyway, I already have cut and assembled all struts, I won't change it - but for another and future version I might prefer the L3 over the 4V variant. Ln vs nV:
Pitching the Dome The last days were very sunny, but night and day temperature difference up to 15°C which I like to avoid to expose the bamboo struts - as I would expect them to crack more likely. So I likely wait a few more weeks before I make the first pitching of the dome skeleton. Content:
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