Dome unbuilding: July.

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It took a while to remove all the panels. The hundreds of screws were only the few required to hold the panels onto the skeleton. There will be many more when the gores are rebuilt with sealer/adhesive. I bought a cartridge of RAW glue/sealant but can find nothing about it online.

A trial piece of ply and strut were glued and screwed together and left to set. Two hours later, at 75F, the exposed paste was still soft when poked with a screwdriver. Three hours just coming up so I'll check again.

The ply could still be peeled lengthwise off the timber strut after 3.5 hours @ 77F. So I did a destructive test rolling the ply sideways with my bare hands and it finally came apart as can be seen. The adhesive seems quite rubbery at this stage so still offers some flexibility. The glue bond has sheered rather than lifting away from the wood or ply surfaces. Worth persevering? Perhaps I should make another test with fresh ply, glue and timber but leave it overnight for a better strength test. NOTE: An expert suggested these adhesives need much more time than this to cure properly.

Meanwhile I had removed all the covering panels and stacked them in [numbered] clockwise order. I have a new, finer carbide disk for the angle grinder. The 24 grit was too coarse and fierce so I bought one of 36 grade. This is much kinder to the ply and still allowed me to quickly flatten the ribs and struts. Coarse sandpaper disks wore out fr too quickly when tried on this job.

After making several buckets full of sawdust with the angle grinder, I moved onto the orbital sander to smooth things out. The panels had been a bit lumpy when screwed on. So flattening the skeleton surface a bit more was probably worth the extra effort, dust and noise.

Thursday:  I started to dismantle the dome so I could glue the struts together and to the ribs. This is what 140 x 6m x 30mm [1/4" x 1.25"] screws, 280 oversized washers and 140 nuts look like in A4 stainless steel. Ten sets per pair of ribs. I had numbered all the horizontal struts and panels with a permanent marker so I didn't lose track during the dismantling. 

Yesterday I drove to the city to buy the advertised Sikaflex 291i marine sealer. No stock, but they had Sikaflex 591 in black. Then charged they me double as if it really were 291i. So then I had to wait at customer services while they queried the price. Then get a refund. No technical information on the 591. So much for professional service!

Sikaflex-591

Now I am back at home I checked into 591's qualities. It sounds nearly miraculous so my dome should easily outlast the pyramids! I also bought a sturdy wallpaper roller for flattening the edges of the plywood during gluing. The roller should even out the adhesive-sealer bed without moving the panels around as might occur with finger pressure.

Click on any image for an enlargement.

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