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Ok, it's been a while, so here is an update on my 18" Dobsonian.
Secondary Rings:
These were completed and ready for staining. Two rebates were routed for the primary focuser board, and a second, smaller board (I'll explain later why I needed to add a second board). I shall refer to this smaller board as the "Secondary focuser board".
Kydex Inner Tube:
Because I never had time to thoroughly source Kydex in enough quantity for this project, I decided to use 3mm 3-ply plywood. This was flexible enough to bend into a 19" diameter tube. It was then glued into place and trimmed.
See the Attached Thumbnail 1.
I manage to find a "Kydex-type" material at my local art and craft shop, in the form of A2 art folios. I cut out lengths to glue on the outer surface of the tube, between the rings. Attached Thumbnail 2.
Focuser Board:
I laminated three layers of 5mm 3-ply plywood using a bending jig. Unfortunately, when it was dry, it had a warp or twist to the board, so I fitted it to the rings, and trimmed it to a more even curve. Unfortunately this left a less than satisfactory surface for staining, so I decided to laminate the focuser board with 3mm 3-ply plywood strips. Look at the Attached Thumbnail 2, 3 & 4. These images show both boards with laminated 3mm 3-ply on their sides. I have yet to laminate the top surfaces of the boards.
This error simple came down to the lack of tools and a proper workshop. But that's okay. I'm not fussed with it.
Secondary Focuser Board:
I added a second board to mount any future electronics, finderscopes etc.
Secondary Truss Tubes:
As careful as I have been to keep the truss tube aluminium clean and scratch-free, it was hard to keep a nice brushed surface. So by pure luck I found "Contact-type" vinyl adhesive (similar to which is used to cover school books), with a brushed brass surface. I will cover the aluminium tubes with this material.
Well, it still looks a long way off from being completed, but with everything else happening in my life at the moment, I should still fulfill my completion date of December 2008.
A Note About Weight:
Weight. Some may say this is too becoming too heavy for a secondary cage. Too much timber. It needs to be lightweight. While I fully understand this argument, I do not see this telescope traveling very far from home. In fact, I will probably remain assembled when not in use.
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