I needed to make several sets of wooden rings for the project. One ring will be at the base of the wall, one on top of the wall and hold the wheels, another is attached and reinforced to the bottom of the dome while another is halved and used to box the shutter window on the dome.
I used 12mm plywood for this job. Plywood comes in many grades and cost per sheet can skyrocket depending on the grade of ply you buy. This was the most expensive part of the project.† Structural ply at Bunnings is $45/sheet and with this dome one sheet makes 2 courses of a ring. I need 3 rings with 3 courses and 1 ring with 2 courses plus litres of glue. I opted to buy one sheet of structural ply and laminate one course of that into the 2 top rings and use non structural ply for everything else. Non structural ply is still $33/sheet and I needed 6 sheets L
The plan was to cut the ply into arcs, then lay the arcs into a ring and laminate rings together using glue and screws. Once you have a ring, you make a huge compass with a router on the end and correct any errors in the wood and make it round. Normally wood and I donít get on but in this instance it seems to have worked.
A quick search of the shed revealed about 8 litres of white acrylic undercoat and 10 litres of a sort of beige acrylic timber colour. I think these came from a large pergola I built, 2 or 3 houses ago. 2 coats of each where used to seal the rings. †These images show the bottom ring of the wall which is 2 laminated layers of standard ply wood.