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I remeasured the diameter of the dome now that it is a complete unit. It continues to measure 4.1m across the diameter. 4.3m across the diagonal. A difference of 30-10 = 20cm or 8" of ovality!
This
leaves me with a problem. I had calculated the building to be a modest
4m in diameter at the top. Thinking the margin of difference of 15cm
[30cm/2] would provide plenty of internal clearance. 10cm difference
would still cover the building against run off from the dome. Yet
offers rather less physical clearance than planned at only 100/2 = 50mm in radius across
the minor axis.
I could use ratchet straps or stiff cross struts. To pull/push it into a truly round shape. Then place a tightly fitting, plywood ring of the desired diameter inside it to hold that shape and dimension permanently.
I
think it is probably unlikely to make much difference. The sheer size
of such a ring means flexibility in all planes. The plywood must be
laminated from short [1.5m] arcs. Leading inevitably to further
flexibility. The dome is also heavily reinforced with a rib a few
centimetres above the skirt. This moulded in rib will probably make it
difficult to impossible to change the shape noticeably.
At this stage it might be easier to replace the cross bracing in the top ring of the building. To shrink the top of the building slightly and then live with the dome's ovality. GRP is known to be prone to unpredictable warping.
I have noticed that it is possible to flex the skirt by hand.
So I could temporarily push some 2x4s braces across the diameter. Just
to see if it helps to obtain a rounder form. Though care is obviously
required to avoid cracking. If the distortion returns over time I might
regret not having reduced the building's diameter. It would be a major
task to remove the cross braces once the building is clad in plywood and
has a thick plywood ring attached on top.
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