23.01.2021 Expanded building footprint using arc templates.

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After lunch I laid out the re-cut arcs and they fitted perfectly for an inside diameter of 4m. So I moved them over to the octagon and laid them in a ring around the building. Being careful to butt the joints neatly together. Then I measured all the distances between the arcs and the octagon's corners. Finally I measured the shortest route to the octagons walls from the inside of the arcs.

All the figures were safely entered in my notebook. My habit of scribbling on scraps of paper was never very reliable. 

Next I scribed lengths along the inside of the arcs for the new post spacing. Twelve posts spaced at 85cm centres, on a 4m diameter circle, proved to be just right. 

Then I tried an upright rod to see where the new posts would fit onto the veranda joists. It should not be too difficult a task to tie them all into the existing structure. Only in the W and SW did the posts lie well outside the veranda. I shall have to bridge to these with new joists attached to the originals. 

I want all of the new posts to be load bearing. So the octagon's posts can be safely removed if necessary. Though it may prove more useful to leave some of them in place but chopping them off at observatory floor level.  Leaving the observatory floor clear. Right out to the new and much larger footprint. 

There is no further need for the old posts to support the smaller diameter top ring of the octagon. Except in the east. Where I will retain the two original posts nearest the shed.

Now I can go ahead and dig the holes for the 12 new posts. I have a narrow, trenching spade to keep excavations to a minimum. Though it may well prove more efficient to dig a trench at 4m diameter. Rather than digging narrow, steep sided holes with gravel constantly falling back in. The last time I laid these blocks for the octagon was during a dry period. When damp, the gravel is much less prone to flowing downhill.

The images show the template ring arranged around the existing building. The centres of the new building [foundation] blocks and posts will lie on the inside of the ring. Leaving the shrubs on the outside safely untouched. They provide shade, wind protection, colour and interest.

The twelve, much narrower walls, will give the larger building a much smoother, external appearance. Far more rounded than the present, rather flat-sided octagon. I would never build another octagon. Too inefficient of usable space for the ground area covered.

 

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