19.09.2021 Shutters and top boards.

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Sunday 19th 57F, overcast.

The laminated shutter zenith boards were successfully glued overnight. So I un-clamped, trimmed and roughly sanded them to match the pattern. 

The dome slopes upwards where the boards will sit. So they ought to be relieved slightly at the back to ensure clearance. I had placed the edge of the observation slit cut-out deliberately beyond the zenith. Just to ensure rain did not collect behind the zenith board. 

The overhanging shutters will help to shelter the twin boards. They also enjoy natural drainage from the curvature of the dome. So I shall leave them as they are to rest lightly on the dome. This will help to unload the drawer slides during their normally closed condition.

The top of the ribs will be brought upright by sturdy angle brackets. Which will securely connect the corners of the shutters between ribs and boards. Overhanging brackets will join the inner shutter ribs to the boards. These brackets must bridge over the zenith board with clearance. Otherwise they would lock up the shutters. 

I had notched the inner ribs on the plywood dome but didn't much like the potential weakening effect. So I have searched for a long enough bracket to reach over both, very thick, zenith boards. 36mm x 2 plus the depth of the drawer slides. 

I will have to get some furniture assembly, tension dowels. To avoid using wood screws into the plywood end grain of the shutters to hold these inner brackets. Which is guaranteed to split the plies.

I have now removed the second outer rib and routed a chamfer on the outer edge. This will improve the weather seal and allow the GRP cover to rest more evenly on the outer rib. I had already chamfered the other, outer rib.

Both outer ribs are back in place and the brackets fastened. The shutter top boards are in place. Held by angle brackets I made from 10x4" roofing, hole plates. I may replace these if I can find something more sturdy with equal legs. 

I need longer brackets to connect the ends to the inner ribs to the top boards. The brackets I have aren't long enough. While being unsuitable for mounting on the top edge of the inner ribs. I may mount angle profiles in line with the ribs to help support these brackets.

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