9.04.2021 Of slides and arc radii.

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Friday 9th 41F, wet and very windy.

I am expecting some parcels today. The drawer slides and the Stanley Surform tools. The latter have arrived but will have to wait for a lull in the rain. Before I can  practise on the sawn edges of the GRP. I wonder if they would work on the birch ply arcs?

The drawer slides are 50cm long when closed and 103cm long when open. They are very heavy but [?] nicely made. Claimed load capacity is 119kg per pair.

Yesterday afternoon I marked out and trimmed some of my 2m radius, plywood arcs to 2.15m radius. This is to match the 4.3m diameter of the dome. In readiness for building ribs and the base ring[s.] As soon as I held the first arcs against the inside of the dome skirt they were, quite obviously, still too small in radius. They all rocked at the centre all around the dome skirt. 

I have checked and double checked the diameter of the skirt. Doing so across many diameters with my laser rangefinder and several tape measures. I double checked the radius bar and the arcs I had drawn and sawn with the jigsaw. Something doesn't quite add up. 

The Bosch jigsaw is hopeless at following a line. Though but not bad enough to change the radius of a curve by that much. It also tips the blade badly with each attempt to change direction. Still not badly enough to alter the radius of the curve. More investigations will follow. Rain permitting.

It cleared up as 10am approached. Even some sunshine. Though it remained windy. 

The problem with the radius of the arcs is due to variations in the fibreglass layup. Plus the facets. It looks as if I shall have to make each arc match its exact position. Not a great deal of extra work if I use an existing arc to check what is needed. I'm still waiting for the new router bits to be despatched.

Having the meter wide off-cut from the roof of the dome I decided to have a play. The first thing I discovered is how flexible the GRP was lengthways. So I can freely dictate the shutters' vertical radii via the ribs. They will easily conform. 

The full sagitta of both shutters, across their combined, 1m width, is only about 6.5cm. Nor startling, but enough to look quite smart compared with traditional, flat shutters.

There is enough material for one spherical triangle in the 1m wide off-cut. With plenty of spare material from the shutter segment for the other. The images show a couple of quick mock-ups. I just leaned the 1m wide off-cut against the dome. The dotted lines on the outside view show the trim lines. I think the triangular "patches" will be all but invisible from the ground.

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