22.02.2021 Got wood. Now what?

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 Monday 22nd. 37-53F. I am now the proud owner of 30 [ugly but remarkably straight] lengths of 4.2m [13'10] of 50x100 [2x4.] 

I am playing with options in my head for full height, wall frames. Run one narrow edge of the 2x4s through the saw? To bevel the posts for the face dihedral between the wall sections? 

Or, make square faced frames and leave a wedge shaped gap between them? This option would leave unsupported edges, a wedge shaped gap between the posts and plywood spacing problems in mid air. Not a great idea!

The first option brings the edges of the plywood cladding edge to edge and fully supported. Though I'd need to drag the table saw out of the shed to work the 4.2m long bevels outside. 

The best and most obvious option brings the 2x4s flat against each other on the long face. So they can be easily bolted [or screwed] together. They will also fit more neatly on the steelwork on top of the foundation blocks. This option also demands mitres on the ends of all the frame spacers. So the mitre saw will enjoy some exercise as well. It's lucky a whole week of mild and dry weather is forecast.

The wall frames ought not to have cross braces fixed at their very ends. [Top and bottom] Or fixing the frames to the steelwork will coincide with the brace fixing screws. The top cross braces ought to be placed directly under the building's top [roller supporting] ring. How best to judge that height before it is decided? 

I don't want to have to separate the new wall frames to move the top cross braces up or down. There is no easy way to access the cross brace, fixing screws once the 2x4s are fixed together. Though toe-nailed screws could be used from below. Nor can I [so easily] use the 360° laser level to set the frame tops accurately. Not while the skirts are in place on the old building/dome. 

My present plan was to have the new [plywood] top ring only slightly above the old one. This would allow me to leave the octagon's old top ring of timber 2x10s in place for as long as possible. I'd need top access to the long screws I used to fix this roller ring down onto the 4x4 octagon posts. The plan is to [eventually] saw off most of the octagon's posts at obs. floor level once I have the new, wall frames raised and fixed. However, the two eastern wall posts will remain much as they are. 

Here I am trying to look ahead to removing the old dome and to move its supporting/rotation rollers. Fortunately the new building footprint will all fall outside the octagon. Except for these two eastern posts. So there is a decision to be made regarding interference between the two buildings at the eastern wall during the dome changeover. If I opt for a cross brace position, to have the new top ring lying on top of the octagon, then I can fill in the missing gaps at NE and SE later. 

The foundation block steelwork screws allows some inches of height adjustment. So the top ring could be lowered to the same level as the octagon's top ring once the new building becomes fully structural. 

Using the 360° laser will make it child's play rather than a several years of continuous doubt. Using water hose levels, long straight edges and assorted builders levels and inclinometers used up countless man hours. The new laser level took only two seconds to confirm that I had achieved near perfection on roller height. Only the dome base ring was a bit uneven.  

For simplicity, no wall frame will be used on the eastern side of the bigger building. It is perfectly adequate as it is. The two posts are simply slightly further apart than all the new ones. It would have been very difficult/almost impossible to excavate holes for new foundation blocks between the two buildings. So why bother? I opted to leave the eastern wall and its posts well alone. 

By accident this deliberate choice twisted the new building more truly north-south. The octagon was better matched to the orientation of the house. Which faces slightly west of true north. Meaning that the telescope mounting was twisted slightly on top of the huge pier. Which was also aligned with the house. An oversight at the time of building the octagon through raw inexperience in designing observatories.

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