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Saturday 2nd January 2021, overcast and misty start cleared to brief spells of sunshine.
Talking of spells: I had to remove 35 litres of rainwater from the collection trays on the dome base ring today. That's about 7 gallons in Olde Money. The magic broom was still hungover from New Year. So my spells didn't work on that.
It was back to manual labour. Up and down the stepladder, carrying a nearly full bucket, four times. Now I feel just like a cartoon character. I just wish it was a stronger one. A superhero would do nicely. I should have rigged up a large funnel and hose out to the surrounding ground by now. Perhaps I need the physical exercise more than the mental variety?
The cladding is grooved ply and each sheet will provide 2 full lengths. This will only reach the observatory floor level. The extra height demands sheets be cut down to match the required height. Leaving a [potentially exposed] horizontal joint in the cladding at roughly 3/4 height of the building.
The next decision is whether to build panels for more rapid construction. Rather than adding the cladding sheets to the completed, but bare skeleton.
Panels would be heavy and long [4m tall] but greatly reduce the need to clamber all over the building. By ladder, to add the necessary, hundreds of fixing screws. With the risk of slippage and geometric inaccuracy when fitting the cladding sheets. A dihedral angle [mitre] would be required on the vertical posts at vertical panel junctions. Easily managed with the table saw.
I wasted hundreds of hours individually cutting mitres on every piece of timber in the last, building skeleton. I was having to compensate for twist, spacing and bending of the 4x4 uprights and the heavy timber being used for cross bracing. Often needing several cuts to get a perfect joint.
Meaning a return to the ground to make the saw cut. Then back up to check the fit and angle. Repeated, several times, for every single mitre, it all added up to a huge amount of wasted time.
Vertical panels would all be identical units and have all square joints. The tops could be lifted into place with a pulley or winch after the bottoms were pushed against the building. The foundation blocks would all have to be perfectly spaced and not disturbed during fitting. The upright tops would be clamped at the underside of the top ring before fixing.
Panel design is variable within the fixed size format. Diagonal bracing and only 50mm thick? Rather than 100mm deep with the uprights framing the edge? A horizontal batten would be required at the joint between cladding sheets for edge support.
Reaching the entire circumference of the building with full panels would be very difficult if they were heavy. At least 12m of 2x4 plus cladding. I'm not superman. Though safe access at obs. floor level would be possible from the existing building. The panels could be walked around.
However tempting to go with panels, I'm seeing repeated heavy lifting at every stage.
Assume pairs of 2x4 uprights, Each post lifted, fitted and then clamped together individually. Rest on the ground bracket and then a tack screw to a 2 layer top ring. Brace the uprights afterwards. Because there is no really need for structural strength until the dome is fitted.
A distortion free and self supporting, external shell is all that is required. I am only enlarging the footprint at this stage. Beef up the top ring with more layers of plywood once it is supported by all the uprights. This will avoid having to raise the huge and still flexible top ring in one go. Which was extremely difficult even at 3m diameter on the last build. I can carry smaller arcs up and clamp and screw them.
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