Building the Octagon Pt.11 Observatory floor.

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A member of the CN forum has kindly suggested a really solid floor plan and even provided a drawing. It is far better than anything I might have come up with.  My solutions would have involved lots of oddly angled joints with radial joists. His plan uses parallel and doubled 2"x 8"s across the major diameter of the octagon to act as main support beams. The rest of the joists are 2" x 6" and all parallel, but at right angles to the two main beams using short, stiff spans. Now I shall have to obtain more timber and get building.

I intend to leave the walls and ground floor open for the moment to provide firm footing for ladders and scaffolding. If I built the ground floor first it would be exposed to the weather and physical damage for quite some time. It would also require quite a large step up from the surrounding area. I'm not sure it would help improve access for working on the raised obs. floor.

The image shows how the jointed builder's stepladders provide a perfect trestle height for fixing the upper floor joists in place. They just need some suitable planks [or 3/4" plywood?] to walk on and local lashing to the framework for greater stability. With the octagon walls open I can easily arrange the trestles inside and outside the framework. The extended ground braces add remarkable stability compared with ordinary ladders.

These mini-scaffolding/stepladders are probably intended for working from firm, flat floors. Though the large rubber feet don't sink far into the gravel. I sawed out some trestle planks from 20mm Baltic multiply. With all the ladder rungs supporting the boards along their entire length there is no bending moment to worry about.

Click on any image for an enlargement. 

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