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A photo of the redesigned dome at dusk. Twelve gores out of sixteen and it is hardly more than a half circle. The diameter is about eight inches more than expected! Eek!
The ratchet strap was my attempt to pull the sides in. It worked but opened up gaps between the ribs at mid height. The full length ribs have also risen by about six inches at the dome's pole/zenith.
I have covered the dome over for the night to have a rethink about what I am doing.
Perhaps the new strut lengths still aren't remotely optimum? I'll clamp more upper rib extensions in place tomorrow to see what happens.
Tuesday: Spent the entire morning removing struts and adjusting what was left. Back to squeezing the base into a 10m polygon. I made a simple height gauge with an alloy pole and disk of plywood. Both the ladder and the plank were too bulky where the ribs wanted to rest. Added more rib extensions sandwiched between the gores. This adds about 6" to the circumference!
Later I made more gores from the spare rib arcs. I don't think the remaining struts are the correct length or have the right angle cut on them. The 2nd and 4th ring of struts certainly weren't correct because they forced gaps between gores and made the full ribs too high at the center. Even now the ribs are all over the place on center height.
Measuring and averaging the widths between the ribs, at the standard strut heights, seems sensible. though it assumes the existing struts are the correct length! Too many unknowns!
The latest image shows the result of averaging the spacing for relaxed, gores without lower and upper struts. One complete gore has four, new horizontal struts. It meant cutting yet more, but longer struts with careful attention to the compound miter angles. Fortunately I can sneak up on the required length from below thanks to the tapering of the gores. I kept cutting and trying until the strut would slide into place without distorting the ribs outwards. Then a final check for rib flatness against the shed wall.
Tomorrow, if it is dry, I shall glue the top extensions to more ribs and try them with the new strut lengths. Unless I build at least two gores each time and clamp them together, it is difficult to judge the results. Even then it takes a few more gores to discover the finished dome diameter and geometry. Visualizing the spherical geometry involved from any changes does not come naturally to me. No doubt it gets easier by one's third or fourth dome. Unfortunately I am not about to make a career of it at my age.
Tuesday: Spent the entire morning removing struts and adjusting what was left. Back to squeezing the base into a 10m polygon. I made a simple height gauge with an alloy pole and disk of plywood. Both the ladder and the plank were too bulky where the ribs wanted to rest. Added more rib extensions sandwiched between the gores. This adds about 6" to the circumference! Later I made more gores from the spare rib arcs. I don't think the remaining struts are the correct length or have the right angle cut on them. The 2nd and 4th ring of struts certainly weren't correct because they forced gaps between gores and made the full ribs too high at the center. Even now the ribs are all over the place on center height.
Measuring and averaging the widths between the ribs, at the standard strut heights, seems sensible. though it assumes the existing struts are the correct length! Too many unknowns!
The latest image shows the result of averaging the spacing for relaxed, gores without lower and upper struts. One complete gore has four, new horizontal struts. It meant cutting yet more, but longer struts with careful attention to the compound miter angles. Fortunately I can sneak up on the required length from below thanks to the tapering of the gores. I kept cutting and trying until the strut would slide into place without distorting the ribs outwards. Then a final check for rib flatness against the shed wall.Tomorrow, if it is dry, I shall glue the top extensions to more ribs and try them with the new strut lengths. Unless I build at least two gores each time and clamp them together, it is difficult to judge the results. Even then it takes a few more gores to discover the finished dome diameter and geometry. Visualizing the spherical geometry involved from any changes does not come naturally to me. No doubt it gets easier by one's third or fourth dome. Unfortunately I am not about to make a career of it at my age.
Click on any image for an enlargement.
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