24.01.2021 Juggling the building's cladding panels and posts.

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Sunday 24th cold and grey with mist but light winds.

Just another mental rehearsal: Nothing to see here. Move along please! 😉

The more I think about the expanded building the more I favour raising pre-made panels. Balancing 2x4 upright posts individually, from an adjustable bracket at ground level, isn't easy. If I assembled the full panels down on the ground they could be shoved against the brackets and pushed upright. Then steadied with a timber brace, or an open, builder's stepladder, leaning against the plywood cladding. The ladder's cross braces at top and bottom, with big rubber feet, would add breadth and friction to keep the panel nicely stable.

I can then climb the stepladder inside the building to fix the tops of the panels together. The depth of the angled, paired [2x4] timber posts does not offer itself to spring clamps. G-cramps would probably slip off. So, I could use roof, nailing plates with screws on the inside faces of the vertical posts. A quick and very secure fix using a rechargeable drill, Torx screws and Torx driver. 

I have 'proper' nail plates nails but they are best added after a secure screw fixing. Screws are not approved of because they are hardened and will break under heavy loads. The nails are short and sturdy and have ridged shanks for grip.

As the panels are raised they would become self-supporting by friction between the long vertical edges. Single 4m lengths of timber would not be remotely stable when upright. They would need something to lean against which retails them to prevent dangerous toppling. Panels give me the freedom to add the top ring afterwards. Rather than relying on it for post fixing security. Panels free me from having to find a nearby joist to get a safe, post fixing.

A panel would consist of two, 4.2m high, metric 2"x4"s at the vertical edges. With at least three, 2x4 cross braces. One at the base, another at the horizontal joint between two cladding boards and a final one across the top. The lower panels could be diagonally braced inside. While the panel cladding provide vital, stressed skin effect bracing it could be subject to distortion under heavy wind loads.

Timber length per panel:  2x4m = 8m. Plus 3 x 84cm = 2.5m cross bracing. A total of 10.5 metres of 2x4 per panel. I'll weigh some 2x4 and calculate the expected panel weight. Online spec is 3.3kg per metre for 47x100 planed timber. 14kg per 4.2m length. So 28kg for two uprights. Say another 10kg for the cross braces. About 38kg + plywood cladding. Quite "lumpy" but not impossible. The diagonal bracing can be added later.

The lower cladding boards would be 9mm plywood, 2.4m high x 85cm wide. The top panels [at observatory wall height] could be added afterwards to keep the panel weight down. Depending on actual experience of handling the panels. It might be safer to fully clad the panel rather than fitting the top boards from a ladder. Which would require at least three hands, several tools plus screws.

I could use a top pulley to bring the panels upright after pushing the bases up against the building. Once upright, I can use levers to lift the panels into the foundation block brackets.

The [12] plywood clad panels would come together with a dihedral between the vertical 2x4 posts. Suggesting I saw long wedges on the table saw to close these gaps. Which would beef up the joints into solid timber. Otherwise there would be a gap behind the vertical edges of the cladding where the panels come together. With no obvious, mutual location on the inside corners. The wedges would help to align adjacent panels. Or [FAR BETTER] mitre the faces of the 2x4 uprights to match the angle at the joint between the panels. Second image.

One problem which might rise is bending of the upright posts as bought. Selection on site would allow the worst offenders to become the short, cross braces.

I will use aluminium, Z-profile 'drips' to protect the horizontal joints between vertical cladding sheets.

 

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