Teen Dome Closing, Notes on how to close a dome
Saturday, November 26, 2022 6:51 PM
Once the Hootenanny cast dispersed back to N America, we were left with the core Mexican team of Blas, Raul, Gomez, and Ceasar; with Kate and Eli and I for the Monday and Tuesday Nov 21/22; and then 2 days with Scott and Amy Hartwell (Nov 25-26) to attempt to close the Teen Dome. It is a 14 foot diameter dome. made with 14” bags. It went much slower the higher we got with a small team, so it took those 4 days to get within a couple rows of closing in.
The Sunday Nov 27, offered the Tweddale family the chance to close the dome themselves. Eli also needed to complete his ‘environmental chemistry’ class work, so the concrete mix project worked to learn about chemistry.
It’s never easy having your family attack a heavy duty, hot day project like this - especially all tired from travel, hosting dozens, and building for days in a row. But we persisted and closed the dome by dusk...
with the following lessons learned:
- Expect slow downs near the top of a dome. It’s like backpacking, expecting the next saddle to be the pass to easier terrain, that your destination is ‘just around the bend. Closing is full of false hopes, till you’re at top. Be patient.
- Don’t over tamp as the dome starts to close. Because you have been tamping rows to flat, you have to ease up as you get higher- tamp less. Tamping too much makes big bulges onto the rows, as the ‘flat surface’ gets smaller and smaller as you close in the dome, resulting in the tamped material flowing down and causing sliding of the bag row. You can buttrrees this with a short or skinny bag. But best to remember that the tamping is less necessary than you might fear, as the earth material will ‘cure’ as the weight of the rows adds. be patient and you will get nice, ruonded, flat bag lengths that stay balanced during the circlular closing.
- Don’t be shy - follow the fixed diameter line and close it as the line dictates. Even if it feels like each row is coming in ‘too quickly’, follow the compass and be boid. Don't keep going higher slowly in order to keep an arithmetic closure. The 'Diameter to Radial’ math of a lancet arch compass is geometric, not arithmetic - close in as fast as the compass dictates and don't worry. Just accept fatter bags than you had been working lower, don’t tamp too much.
While it’s hard to see, here is an example of a ‘dimple’ created by too much tamping as we got closer to the center.
Seen from below, notice how fat the bags are as we get close to close?
I used a bracing, small bag to balance the wonky 2 rows resulting from the ‘bulge’ carrying the bag downward. Because we were going to ‘cut out' the moon window, I chose this area to cut out this disgraceful, un-balanced section that had bulged too much due to over-tamping.