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While the horizontal ring design had certain advantages I could see myself really struggling to build it well. With no self support, nor automatic concentricity, the horizontal rings would have to be arranged on a strong and accurate support structure during building.A drawing showing vertical plywood ribs, with horizontal braces and flat panel segments. The plywood panels would have to be well sealed at all their edges.
Meanwhile, traditional vertical ribs, between gores, provide support and automatically provide the desired hemispherical shape. A ladder can be leaned up against the bare skeleton. With a simple timber crossbar applied to the top rung to ensure alignment and spacing are maintained while working up high. Since the dome must be erected in place, on top of 5' high walls, up on the raised platform, this is not [remotely] a trivial matter!
Though, heaven knows, I would much prefer to work on the ground and have a local farmer's [big bale] loader lift the finished dome into place. The question is whether the access is wide enough for a machine which can easily manage the big lift. Big bales can weigh between 600 and 2000 lbs so there is no doubt about these telescopic loaders lift capacity. The countryside is often littered with huge stacks of bales reaching to considerable heights. Well above my more modest altitude requirements.
Though, heaven knows, I would much prefer to work on the ground and have a local farmer's [big bale] loader lift the finished dome into place. The question is whether the access is wide enough for a machine which can easily manage the big lift. Big bales can weigh between 600 and 2000 lbs so there is no doubt about these telescopic loaders lift capacity. The countryside is often littered with huge stacks of bales reaching to considerable heights. Well above my more modest altitude requirements.
The cross braces between the vertical ribs are wedged into place by the open angle during fitting and gluing. An F-clamp can easily be applied while the glue is drying. A slotted vertical brace can supplement the gluing and screw fixing area of the plywood rib.
In fact the crossbars could be assembled from a cross plywood rib with the slotted and mitered battens glued on top. That would give me a full plywood, grid skeleton but with a softwood batten [gluing and screwing] surface laid on top of the entire structure. This avoids having to fix the sides of the panels to the edge grain of the vertical plywood ribs.
The slot width will have to change to suit vertical or horizontal orientation. Unless I use the full rib width for the ply crossbars. I'm not sure it is worth the extra effort to make two different slot widths while mass producing the mitered battens. That said, ply crossbars will add some weight. 15 x 4 = 60 x 2' [average width] times rib depth [say] 4"? 120' x 4" = 40 square feet. Or one very large 8x5 sheet! I'd better make the horizontal ply cross ribs quite thin!
It has been suggested that I build the dome from sub-assembly segments like neatly cut orange peel. The sub-assembly ribs would employ half thickness vertical ribs until finally joined together to complete the dome. The crossbars would maintain the shape of the unit to allow easier handling than trying to assemble loose components almost twenty feet off the ground. Which suggests that the covering panels are not attached until the dome skeleton is assembled. Otherwise it will be impossible to work from relative safety inside the structure.
In fact the crossbars could be assembled from a cross plywood rib with the slotted and mitered battens glued on top. That would give me a full plywood, grid skeleton but with a softwood batten [gluing and screwing] surface laid on top of the entire structure. This avoids having to fix the sides of the panels to the edge grain of the vertical plywood ribs.The slot width will have to change to suit vertical or horizontal orientation. Unless I use the full rib width for the ply crossbars. I'm not sure it is worth the extra effort to make two different slot widths while mass producing the mitered battens. That said, ply crossbars will add some weight. 15 x 4 = 60 x 2' [average width] times rib depth [say] 4"? 120' x 4" = 40 square feet. Or one very large 8x5 sheet! I'd better make the horizontal ply cross ribs quite thin!
It has been suggested that I build the dome from sub-assembly segments like neatly cut orange peel. The sub-assembly ribs would employ half thickness vertical ribs until finally joined together to complete the dome. The crossbars would maintain the shape of the unit to allow easier handling than trying to assemble loose components almost twenty feet off the ground. Which suggests that the covering panels are not attached until the dome skeleton is assembled. Otherwise it will be impossible to work from relative safety inside the structure.
The ribs will provide support for a tarpaulin during final construction in what must inevitably become poorer weather as winter approaches. This insurance against having to work while fully exposed to the elements will hopefully increase speed, accuracy and comfort. I'm thinking of using net reinforced, clear plastic tarpaulin for its transparency, light transmission and whatever warmth the weak autumn/winter sunshine can offer.
Click on any image for an enlargement.
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