So, over the last two days I have been work on two parts of the observatory project. This thread is about the final stage of completing the Dome base ring which includes the lamination of the last plywood layer, patching the screw holes and joints with builder's bog, sanding and first coat of 4 or 6 of marine varnish.
Why marine varnish, I thought it was a good idea as it will seal the plywood and give a nice surface finish for the rollers to run on.
Cheers
P.S. I did go around and check and relevel the dome base ring to ensure it is with in tolerance and is somewhat level in all cardinal points. A process I will keep doing until the final plywood cover is applied.
The other part of the project that I was working on today was the constructure of the Shutter frame. Same routine as with the dome base was to cut out 13 plywood arcs with an outside radius of 1258mm. Lay them out and align with a tangent arm.
Was thinking of constructing the ring on the pavement but with the treat of rain I move to the garage which was my original plan. The good thing with my garage it that I was able to use the expansion joints in the concrete to centre the tangent arm right where they cross at 90 degrees.
I only had to laminate two layers of plywood together, so the process was quite quick and having done it multiply time it get easier with the trimming, gluing and screwing.
Final task tomorrow is to divide the ring into two semi-circle than hopefully put some studs in to form the opening and attach it to the dome base ring. This will depend on the painting.
Cheers
P.S. The Shutter opening was scaled up to 690mm due to the fact I have scaled up the diameter of the dome from 2.3m to 2.6m
Need to get the car back into the garage so decided to cut the shutter frame in half early.
Using the tangent arm, I made sure the Shutter fame ring was centred, then ran a string line across the circle ensuring it passed over the centre to give me a line to cut by. Also ran a string line 90 degrees to the first to mark in what will be the top of the semi-circle, tape measure help with squaring the lines.
Once done, cut line marked in then a quick cut with the saw. End result to evenly matched semi-circle.
Very happy with the result.
Cheers
Last edited by anthony2302749; 02-06-2024 at 09:31 PM.
Today's part of the project was to construct the Shutter frame proper. First task was to recheck the maths to ensure the height of the frame is correct in relation to the dome base ring and that the future dome ribs will fit correctly (I have an idea for that but have to wait till next weekend). Removed 36mm from each end of the Shutter semi-circle. After this task I got the desired height of roughly 1348mm (1258mm height of Shutter semi-circle plus 90mm for the support blocks not including the window packers)
I then made 3 by 1" thick plywood studs (Not entirely happy with the end result of two, they may get the flick) to secure the Shutter semi-circle parallel with each other and squared front and back. Final task was to add additional studs of 42 x 19mm Pine which I repurposed from an old screen which I had made years ago, and which was heading to landfill.
The Shutter width is 690mm (27.1") with and opening past zenith of 178mm (7"). Rule of thumb for the opening past zenith is half the aperture of the telescope diameter. Which of cause came from the web some were maybe Cloudy Nights.
Cheers
P.S. The Dome base ring got a final coat of marine varnish, four coats in total. Tomorrow with the help of my son, going to flip the dome base ring, centre, level and mount the Sutter Frame.
Last edited by anthony2302749; 02-06-2024 at 09:18 PM.
This evening, flip the dome base ring, centred, levelled, ran a string line to obtain equal halves. Then measured ran a string line 90 degree to the first to obtain equal quarters. Remounted the Shutter frame and centred.
Still not liking how the Shutter frame end pieces which sit on the dome base ring look, I think I can come up with a neater solution.
That's looking AMAZING!
The mention of marine varnish, I learnt a long time ago the quality in the timber and finish is what makes it last. I've tried the cheap options in the past for various projects, never again where timber and finishes are concerned.
Ah, my sister is visiting Melbourne from Queensland and sent me photos yesterday of clear blue skies, I dream of those things but rarely experience them, it raining again here for the past 3/4/5/...days.
The long weekend is a pond us, and for me more construction work on the dome.
Today's effort was to complete the pair of 90-degree Ribs. This of course involved more routing however the math on this was easy as the ribs are the same radius of the base ring.
So, for the pair of 90-degree ribs I need to cut out 6 plywood arcs. I started to assemble one by placing the plywood arcs on the dome base ring but found it didn't work the way I hoped. Only advantage was cutting the correct angle of 90-degree ribs which mate to the shutter frame. Went to method B, that is clamp two plywood arcs together, line the top to the shutter centre and line the bottom to the quarter mark, adjust to the desired length by loosening and re-clamping. Once I was happy, I added a small fudge factor in of 5mm in and glued and clamped all pieces together.
Once I had completed the first rib, check my work against the shutter frame and ring and made adjustment by trimming each end of the Rib until I had a nice fit. Rib one became templated for Rib two and I knock it out very quickly.
Once I had two complete Ribs, I clamped them on to the Shutter/dome ring Base. Made some further corrections in measurement regarding equal halves and quarters. After this I started to make 90-degree Blocks to use as brackets instead of metal ones, I think it looks nicer. Also gives me a point for clamping the plywood cover later on.
Cheers
Last edited by anthony2302749; 08-06-2024 at 08:39 PM.
Today's task was to fix the Shutter frame and 90-degree rib to the dome base ring. Plus, route out and assemble four 60-degree ribs.
Same method was used for 60-degree rib as with the 90-degree rib. But as the 60-degree rib attaches lower I need to measure down 210mm from the top of the shutter frame, more maths. Using a bevel square, I obtained the correct angle so that the rib sits flush to the shutter frame. Then with the help of some clamps I adjusted the 60-degree rib until I got the right length and top and bottom of the 60-degree rib sat flush. Glued, clamped and screw the rib together ensuring to leave a few extra millimetres as a fudge factor.
Bevelled the top end to get a nice flush fit, trimmed 5mm of the bottom and the first 60-degree rib was complete and ready to be used as a template for the other three.
The other three ribs have been constructed and are sitting on the decking.
Cheers
Last edited by anthony2302749; 08-06-2024 at 05:28 PM.
Since my last post which wasn't that long ago, I have bevelled and trimmed the 60-degree ribs and clamped them into place. Beginning to look like a dome. Did make one cutting error with a rib, cut the bevel on the wrong end from where I had marked it, obviously forgot to "measure twice, cut once". However, had plenty of fudge factor to play with, so no real concern.
Next task is to fix the 60-degree ribs to the Shutter frame and dome base ring and get started on the four 30-degree ribs.
After a day visiting the Lume and lunch with the family I only had time to fix the 60-degree ribs into place and flesh out the final 30-degrees Ribs.
Same process as for the 90-degree ribs. Remeasure, drill, glue and screw the top of the 60-degree rib to the shutter frame and then remeasure, glue and nail the bottom of the 60-degree rib to the dome base ring. Job done.
Also fleshed out the last of the ribs, that being the 30-degree ribs. So, tomorrows job is assembling two pair of 30-degree ribs and hopefully have them fixed in place by the afternoon.
By the way, three sheets of 2400x1200x12mm plywood nearly made the distance had I not made some erroneous cuts on the second sheet while constructing the shutter frame. The piece of plywood that were intended for the shutter frame are now being repurposed as plywood brackets as seen in the pictures.
So, will need to buy roughly a 1200x1200x12mm plywood sheet to construct the ring that will be used to support the rollers and sit on the observatory wall structure. Will worry about that later.
So, today's effort was to complete 30-degree ribs but alas I ran out of plywood to finish the last rib. What I did get to complete today, well at least three 30-degree ribs. All trimmed, glued and screw into position using the same method as all the other ribs in this build.
With the use of a plane and belt sander I bevel the top end of 30-degree ribs so that the sit flush with the Shutter frame. Pretty pleased with my carpenter skill so far.
After buying another sheet of plywood the dome frame is finished.
Last rib when in this morning marking the end of the dome frame construction. Also sand down each rib and filled in the screw holes to get the frame ready for covering.
So, with the finishing of the dome frame the next step is the covering of the dome. For this task I am creating three cardboard templates to be used to help cut out the 3mm plywood sheets. Two templates are complete the third one will be done tomorrow. By tomorrow afternoon should have several plywood panels cut out and attached to the dome frame.
Last rib when in this morning marking the end of the dome frame construction. Also sand down each rib and filled in the screw holes to get the frame ready for covering.
Looking good Anthony. You re going to have to restain your deck when you're finished
Cheers, Richard
The trial and tribulations of applying the covering.
So today I was hoping to get a bit more done in the way of applying the plywood sheeting to the dome frame, however things did not go to plan.
Making the template was relatively easy and cutting the plywood sheeting not much of a challenge, however affixing the first segment went south quickly. In my mind I was hoping to be able to fold the plywood over the shutter frame, in practise I destroyed a good piece of ply. So back to the drawing board for a new idea.
The solution was to rip a piece of 40x19mm pine with the circular saw set at an angle of 22 degrees. Good thing is that the pine been sitting out in the weather and therefore quiet damp which makes it easy to bend into shape. Glued and clamp new 22-degree piece to the shutter frame, tacked with stables. Modified the template, cut out a new piece and put it into position once the glue had time to dry. Success, the piece went on nicely.
So, in the long run I manage to get two pieces attached today.
So, since my thread I've been hard at work installing the 3mm Plywood panels. Let's say it is the least enjoyable part of the build as there is a lot of fiddly adjustment along with a bit of cursing and blood, put the drill into my finger.
Anyway, while I endeavoured to get the templates correct, thing didn't fall together as I intended hence the fiddly adjustments. The 22 degrees bevels were installed along the shutter frame, finish of the last two 30-degree panels. Then moved on the last three 60-degree panels (did one last night), these panel were a pain to do in regard to getting them to fit somewhat in line with 30-degree panels, a bit of trimming was required. So, all up installed 5 panels today, all glued screwed and stapled on.
Four more panels to go with one sheet of 3mm plywood left, will I make it.
