Building a 2-metre Octa-Geodesic Dome: part 2

Construction of Base and Floor

My dear lady wife insisted that the observatory would not be a "square wooden shack messing up the garden" and she "suggested" the octagon - bear in mind I have never built anything like this before! I used 3" x 2"s for the outside of the base and 2" x 2"s for the internals. The pieces were securely screwed together with a mixture of 2" and 1.5" woodscrews.

My garden is composed of firm clay and the breeze block foundation was more than adequate. The blocks were levelled and the base laid on top. Note that I subsequently added more supporting joists to the base, as per the original plan, to give it more support.

The base and plinth with the mount and scope fitted - just to get a feel of how it would eventually turn out. I was able to use it as an observation platform at this stage. Note that there is a gap between the plinth and the hole in the base so that no vibrations would be transmitted to the plinth while walking around.

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Construction of Side Frame, and Dome Base & Rail

It's amazing the combined strength of 3"x2"s, 2"x2"s, 4" carriage screws (top and bottom of uprights), 2" woodscrews (all other joints), and, of course, that wonderful stuff ..... PVA wood adhesive.

I had to calculate the internal and external dimensions of the octagonal "rings" for constructing both the dome base and supporting rail in order that the dome fitted securely.

Each side of the base octagonal was joined using a combination of two wooden dowels, staples, and ..... yes, you've guessed it ..... PVA wood adhesive. I worked out in advance that I would need to further trim the rail to ensure clearance of the dome skirt which would eventually be fitted. In fact, I had to trim a further centimetre or so off eight of the corners (making a sixteen-sided figure) once the dome was placed on the rail casters to get the right clearance - not a difficult job though!

3"x2" wooden braces attached to each upright using 8mm diameter carriage bolts and ..... PVA wood adhesive. An extremely strong combination and I didn't have to add the "cantilever" braces I thought I might have to in the original plans. The dome rail was checked for level and attached with two 4cm woodscrews at each support.

Construction of Sides, Door, and Watershed

The outside "skin" for the frame and door was constructed from shiplap. Once the door was on and painted the joints were silicone-sealed and the rail casters fitted.

Initially I attached the casters to the base using small woodscrews but I later replaced them with nuts & bolts and raised the height a couple of millimetres off the base using washers. This ensured the dome skirt cleared the roofing shingles attached to the "watershed" (see below) and provided a much more secure fixing.

The watershed was constructed using eight cut-to-shape segments of OSB board.

Click here to go to part 3.