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Sunday 11th 35F, heavy overcast, windy from the NE with wintry precipitation. Continuous, wet snow falling until at least mid morning so far. 10.30am. The snow is pitching well on the GRP dome and particularly well on the horizontal, spare, roof panel. While the plywood dome is clear. Interesting. I presume the GRP is much colder than plywood.
Plans to cut out the shutters have been put off for a [much] drier moment.
Still no 12mm cladding plywood in stock at the DIY store.
The flexibility of the GRP shutter cut-out really surprised me. At a meter wide it is double that of the individual shutters. How best to judge their required length? Build the shutter and slit ribs first? Then measure those? I still remember the enormous struggle to fit the shutters on the last dome. It was done in place, high on top of the observatory building. I had fitted the top drawer slides first. Getting the shutters to meet the lower slides required crowbars and much trimming of the ribs.
This time I might fit the shutters to the bottom slides first and see where the shutter tops come to rest. They should easily conform to whatever curve I put on the ribs. So the ribs will need to be stiff to cope with the weight. 2x12mm ribs, on either side, glued and laminated, birch plywood should be enough. Any crossbars will need an interesting cross section. A third, central rib on each shutter is possible if it proves necessary. All of this will be done while the dome is still safely on the ground.
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