Dome building: Onwards and upwards!

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But not yet. Today, Saturday 5th May, I braced the slit frame to ensure it was central to the dome and level. Then I started extending the foreshortened ribs up to the slit frame. It seemed easiest to resurrect my Inca bandsaw to trim the ends of the arcs by small degrees until they fitted perfectly. It felt hot in the shade-less 63F of a still and sunny May afternoon. Not to complain, though, since it gives me a chance to catch upon weather delayed progress.

By the time I had finished adjusting the slit frame I had only 5" of clearance beyond the zenith. This could easily be increased by changing the 2"x6" top bar for some 3/4" plywood.

Extending the ribs is a very time consuming business. Perfect length, following the same radius as the lower arcs, compound miter angles at the top, overlapping joints [for strength] and straight line alignment with the lower ribs all adds up. Not to mention the blinding sunshine every time I look up to judge the next cut. Then the work is doubled because each rib is doubled.

I have yet to make angled blocks to join the ribs to the slit framework. Even then I have to cut flats on the tops of the extended ribs. Then add vertical struts to give the top tier of trapezium covering panels something flat to rest on. 

With 72F in blinding sunshine it was getting too much for me. So I threw a worn out, white, lightweight tarpaulin over the dome for some shade. The poor man's, "let's pretend we have a white dome," if you like. It makes a far more comfortable workshop with good light. It seemed much larger inside the dome in white. This is typical because white recedes visually on interior surfaces.

Tuesday & 74F hot again under a cloudless sky. Still plodding on fitting rib extensions where the plywood sheets weren't wide enough for a full arc.

Wednesday and already 74+F by 12am. I finished off the last four rib extensions. The two shorter ribs on the open slit sides will have to wait until the geometry is finalized. If I can get the ribs fixed to the observation slit frame I can get rid of the two supporting props.

I can't say I have enjoyed making the rib extensions. With no desire to waste unused arcs there was a lot of fiddly cutting on the miter saw to get it right. Which meant lots of walking back and forth, in and out, and climbing endlessly over the raised dome threshold. Every time I tip my head back I feel dizzy.  There was a lot of head tipping involved. I presume it is my inner ears causing the problem. As I have been going deaf over the last couple of years after terrible bouts of screaming tinnitus. Tomorrow marks a change to cooler weather with thunderstorms.

Time to use the table saw in anger in cutting glue blocks. The wheeled stand is remarkably user-friendly. BTW: Anyone struggling to park the table saw + stand should put their foot on the yellow plate as if it were a normal sack truck. This works a treat. Where, before, I was struggling to nudge the wheeled stand forwards under the miter saw.

The latest view of the dome skeleton after the ribs opposite the slit were adjusted to the correct height and aligned.

I took the pointless [underside] carrying handle off the miter saw stand to allow the table saw to roll cleanly underneath. The miter saw needs to be set with the miter handle well to the left, or right, to allow the table saw to rest against the curved, pivot casting for minimum projection.

Click on any image for an enlargement.

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