Building the Octagon Pt.9 And then there were seven.

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I managed to raise the 7th post and brace it before I was called in for a shower before dinner.

This is the view from my dormer window where I sit at my computer. It looks as if the top of the Octagon is level with the bottom of my window frame. Pure coincidence as it was not deliberate.

The heavy duty mounting sits under a tarpaulin in the foreground. The pink mast is from a windsurfer's, flea market, clear-out and supports my wireless anemometer. Though it didn't get much exercise today as it was warm and still. A little too warm for my tastes!

I discovered I could brace the previously fixed post with a 2x6 while I rested a ladder on the outside of the octagon.This allowed me to reach the upper cross brace/joist for 4" screw driving with the rechargeable drill. Then I had to dangle from the stepladder to reach the next post.

Today is cooler and breezy with all-day rain, by the look of it. Thank goodness I can take a rest day! Though it might stop raining just long enough to get the last post in. 😉 It didn't. So I couldn't.

One more post and four perimeter joists and the circle will be complete. Then what? First I had better get all the posts braced perfectly upright. I'll have to see whether a full octagon gains some natural resistance to flexure. I had plans for X-frame braces in the lower sections but wonder whether I couldn't achieve more early stability further up in the structure. Horizontal 2"x 4"cross braces might ensure a stiffer framework since they work radially where they enjoy far more "leverage." There is no point in trying to brace the lower sides if the framework is not perfectly true.

There is another Catch 22: I intend to build a sturdy octagon from 2"x 6" timber at the center of the floor structure at observatory floor level. Joists will connect this frame to the perimeter octagon. The problem is not knowing how small I can make the inner octagon and still clear the massive, tapering 4 x 4"x 4" wooden pier rising through the middle of the floor. Isolation of the pier from the floor is vital but I don't want to have to "childproof" a large gap between them.

Then there is the matter of supporting this inner octagon. Having the pier in place would really help to support it to allow work to proceed with the obs. floor joists. The pier timbers are bolted to concrete anchors at below ground floor level. So could be removed if they become a serious hindrance to building work.

That would also allow the final height of the pier to be delayed until the obs. floor is complete. I really wanted to use the existing slotted angle pier. Just to confirm the required height while resting on the finished obs. floor.    

Click on any image for an enlargement.

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