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Wednesday 31st 40F, another sunny day.
My back is aching from yesterday's effort in fetching the cladding plywood. I will have to be careful not to make it worse.
I spent the morning trying to achieve straight lines on the dome for cutting the observation slit. In no particular order: Strong cord, well tensioned: Hopeless. Cheap gaffer tape: Hopeless. Ratchet straps: Pretty hopeless but visibly straighter.
I now have four ladders leaning against the dome to be able to reach the lines from all sides. I have trapped camping foam between the ladders and dome to stop the ladders slipping or marking the GRP. Paving slabs on the ground stop the gently sloping ladders from sliding backwards. Two more stepladders standing against the dome's doorway.
It is impossible to see more than a few short feet of the lines. Impossible to judge, by eye, the lines straightness from any one viewpoint. Logic suggests measuring the spacing between the ratchet straps. Though they could be parallel but not straight. Like railway lines. It would need a flexible, cloth tape. A metal tape, measure can't bend around the dome's curvature. Which means that measuring the arc is a nonsense. It would be longer than the proposed 1m spacing measured between chords. I thought of laying paper strips on the dome but it can't follow a spherical surface. Tensioned items want to adopt a radial position between the start and finish points if they are spaced apart.
I shall just have to wait for semi-darkness and use the 360° laser. Preferably with the head at an even higher position. Higher than the folding stepladder I used last time. The video tripod at full extension still meant the lines didn't even reach the top of the dome. I would never have guessed how difficult such a simple task. As drawing two straight lines, a meter apart, would prove to be.
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