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Image shows the new top track resting on top of the dome. It cannot go any lower without cutting into the dome. Photographed at dusk. The pipe insulation continues to work well in protecting the dome from abrasion by the ladders.
Having converted to channel profile tracks raises a number of issues down at the bottom. Channel positioning is both optional and critical. With many positives and negatives arising from different choices.
I plan to have the skate wheels inboard of the shutters' timber, bottom boards. The wheels and tracks are three times the thickness of the [soon to be discarded] drawer slides.
Outboard: The further away the lower channel rests, from the center of the dome, the more exposed it is to the weather. Channel support from the base ring reduces with greatly increased cantilevering at the ends. Sturdy support will have to be found from beneath the base ring to support the heavy shutters. Leading to potential conflicts during rotation.
Inboard: Bringing the channel inboard, nearer the dome means I have to avoid the inner edge of the base ring. Otherwise my storm anti-lift restraints become blocked. Which would prevent the dome from rotating. I do not favour manually operated latches. It is far too easy to forget them. So I have permanent latches always at the ready in case of storm. I used heavy aluminium disks in the case of the plywood dome. These have worked effortlessly for several years.
A more inward, channel position, provides much more support from the base ring. With considerably shorter overhangs beyond the outside of the base ring. Leading to improved cosmetic appearance. Which are all major positives IMO.
The bottoms of the slit ribs will have to be heavily notched. To clear both the fixed channel and the 72mm Ø moving skate wheels within the track. 75mm + clearance above the base ring. Making oversized notches in the wrong place would be a nuisance. Weaken the rib junction with the base ring and probably end up looking horribly untidy.
The problem is that the slit ribs have to be notched somewhere. To allow me to play with different channel positions. There is presently no room to slide the channel under the bottoms of the slit ribs. So I have chain drilled suitable notches and will use the DeWalt multi-tool to saw out the notches.
Despite the high cost of DeWalt saw blades the latter is proving poor at plunge cuts into Baltic Birch ply. I upgraded to a Titanium coated blade. It soon wore out with only very occasional use. The "ordinary" quality DW saw blades soon wear their teeth down to a smooth stump. Not what I'd call a professional quality tool at all. Though the vibrating multi-tool does have unique advantages. Particularly where no other saw can be brought to bear in a tight corner. The sanding qualities with the small, Velcro attached, abrasive pads are quite pathetic.
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