Dome build: Segment mock-up for a slightly raised dome.


Saturday, the 7th Oct. Rain all day again!

Meanwhile, my shed tidying has made just enough room for two segments to be arranged at opposite ends. With base ring arcs clamped between them to simulate a full dome with 1.5m center height. I checked the base ring diameter and dropped a plumbline from the center or north pole. This ensured the segment bases and tops were equally spaced along the floor.

The lower horizontal struts still seemed to fit fine in their original positions. While the upper struts needed only an inch or so upwards movement on the ribs. I used screws to fix the ribs quite loosely at the pole to a solid vertical batten. This was to avoid altering the relaxed state of the ribs if i had clamped them. Which would have changed their straightness from base strut to pole. Which, in turn, would have altered the required length of the horizontal struts needed to separate them.

The vertical batten provided firm support. With just enough spacing, at the pole, to match the added rib offset from using base ring arcs. Which were deliberately clamped to the the outside of the real ribs for checking whole rib alignment.

Naturally, I can't be sure that this new rib spacing would equate to a complete dome of the correct height. I shall have to change all the segments and then build a dome from the modified segments. Just to confirm  they will all fit together properly. This should be quite a quick job with a rechargeable screwdriver.

Sunday: The image shows the first dome assembly after moving all the top struts upwards. I had run out of clamps at this stage. So I toe-nailed screws on most of the horizontal struts to free up clamps for the extended ribs.

Many of the ribs look as if they are sagging. Now I have to try and lift all the ribs up to the top of the dome. I have already screwed blocks to the upright center post to provide support for the rib extensions.

The second image shows the dome after I have removed all the upper struts and applied all 16 rib extensions. I was all too obvious that the struts were badly distorting the gores. There are still wide gaps around the lower struts do they will have to go next. I hope the ribs remain stable! Or I shall have to clamp them in place between two disks.

The bottom braces set the diameter of the dome so they must stay. I should really have started with full length ribs and gone on from there. Fortunately, tomorrow looks fine again. So I can continue removing struts until the ribs are all perfectly straight. Then I can decide what to do about lightly trimming and refitting the struts further up the ribs.  

Click on any image for an enlargement.


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