Hexagons & Pentagons

Assembling the Hexagons and Pentagons.
Now a 6v icosahedron dome is made up of 360 individual triangular panels, but to make on site assembly of the dome a little easier these triangles are first glued together into six (purple) pentagons, ten (yellow) hexagons, 30 (blue) hexagons, ten (green) hexagons and ten (green) half hexagons... which themselves come in two different flavours!

How the panels fit together (detail of 1/5th of the dome.)
A 6v icosahedron dome is made up of six pentagons and 55 hexagons...
which come in three flavours.
Be very, very, very careful to assemble them in the correct order
if you want to avoid severe mental trauma!

To avoid using miles of duct-tape to hold the triangular panels together while the glue is setting (not an effective solution... as I discovered early on!) I knocked up a jig to hold all the panels in place and clamp them tightly together. The jig consists of a number of support ribs; one for each glue joint between two adjacent panels, and a self adjusting peripheral clamp to hold all the panels in perfect mutual alignment while the glue sets. Unfortunately the jig doesn't do a very good job of self-adjusting and so I found it necessary to pre-align the jig and panels before gluing. Once aligned, all the panels are removed, with great care not to move the jig or support ribs, and glue applied to *both* edges of every panel before once again placing them back in to the jig without disturbing it. The glue I used is an exterior and marine grade wood glue, suitable for joints that will see prolonged immersion in water (i.e. boat building.) It is a water-soluble (while wet) white PVA type glue, so you can easily clean up with soap and water. I picked up a 5ltr jerry-can for about 40euros.

Despite my best efforts to cut the panels to an anal degree of accuracy, small gaps sometimes appear (due to uneven tensioning of the jig or slight warping of the panels) and I found the easiest way of dealing with these was to *not* wipe off the excess glue that was squeezed out of the joins, but allow it to shrink back into the hair-line cracks as it cured. After 24 hours of drying there is actually very little excess glue to be sanded off - It all seems to be absorbed back into the join very nicely. A note of warning to the impatient (like me!): Although the glue will *probably* be set within 12 hours, I found it necessary to leave it at least 24 hours before removing the tension from the jig. I cocked up royally God knows how many times in the beginning by taking the early hex/pent panels out of the jig to admire my handy work... only for the glue to fail while I was removing the excess. Elation quickly turns to a Homeresque D'Oh! Be warned!

Cutting out the support ribs for the assembly jig.

The Ribs are screwed to a central hub and centred inside the assembly jig.

Panels are first layed out and aligned in the jig to ensure a perfect fit and alignment.

Panels are then removed and glue applied to both edges before

being re-inserted into the jig. All edges and corners must be aligned

with each other with great care.

Once all the panels are glued, gentle tension is applied

to the jig and a weight placed in the centre.

Great care must be taken to align the corners of all the panels exactly.

The excess glue is not wiped off. It will tend to shrink back

into the join and help fill any gaps.

Beginning to take shape - Triangles into Hexagons & Pentagons

The Finished result!
(note the different sizes of hexagons)