FreeCAD: Parametric Geodesic Tunnel

This model is available on Github, (I corrected the corners on the bottom plates)
https://github.com/Jeff-Tyndall/FreeCAD/blob/main/GEO-TUN-SS-16-T2-01.FCStd
This parametric model works well, recomputes fairly quickly, because it is very simple. The tunnel itself is made from one part, the triangular panel, and the panel is made of two features. And the whole assembly is driven by two sketches.
The sketches are all driven by the spreadsheet. This model is useful to determine the size of the tunnel and size of the panels themselves, to find good yield of materials. The vertical height of a panel is the length of one line segment of the big (18 side) polygon. The details and joinery of the panels can be created separately, so as to not to overly complicate the parametric model.
Made almost entirely in PartDesign Workbench, with the exception of the Arrays from the Draft Workbench, which is by far the best array in FreeCAD. When using the Array, (I find) it is best to accept whatever it says in the initial dialogue box, then correct the Array from its properties, so you can see the correct modelling.
This model can be created with different polygon shapes and different shape panels. The triangular panels can be right angle triangles, which would make any glass cutting much simpler. An 18 sided polygon works well because it makes a nice whole number of degrees. And has a peak on top and vertical sides at the bottom.
This could also be used to make a container or a lamp shade too.
When copying and pasting bodies, parts or assemblies, remember to deselect the spreadsheet, it should all be driven by the same spreadsheet.

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