…at this point it started to appear that the ‘bird cage’ structure using 15 mm flats would not provide sufficient surface to allow for overlap of the adjacent sections of sheeting and that the holes required for riveting or screwing down the sheets would further weaken and undermine the structure.
Using wider flat bar ribs would have added substantially to the weight of the structure. It was therefore decided to abandon the original idea and go for one that made use of curved wooden beam supports instead. The crown of lags still hangs on the wall as a workshop curiosity and the twenty tacked small brackets were removed from the base ring and some were later used again in the same project.
I looked up several DIY resources on the web that had opted for this solution and I was converted. So I ordered a new consignment of ¾ inch and ⅝ inch plywood sheets and after having tried out the ring rail on the castor racers and spun it round a few times in delight, I gave the rail and the base of the top doughnut a coating of white enamel paint and let it rest awhile.