Building the Octagon Pt.40. Cladding III Director's cut.

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Sunday: Heavy showers stopped play after a few flush trimming runs with the router. It works amazingly well at trimming the 18mm plywood edge back to the post but sprays sawdust everywhere! I should have used countersunk screws to hold the pier panels temporarily in place because the domed heads interfered with the router base plate.

I should also have pre-drilled the screw holes so the ply could lie flat on the posts. These self tapping screws actually push the ply away from the timber posts as they are driven in. I quickly discovered that a short backwards run with the driver would allow the screw to let the plywood drop down flat. The screw could then be driven fully home again.

The showers were soon gone so I could continue working on the pier. The images show the plywood, pier cladding in place and trimmed on all four sides. I had to cut out a deep half circle to within 50cm [20"] of the top of the western panel. This allows me to climb freely through the pier without any risk of my hitting my head. So now the pier looks like a pyramidal dog kennel.

The resonant frequency of the pier seems to have risen considerably with about a one second damping time. I still have to cross brace the pier lower down. This will require that each brace be stepped in height above the ground to spread the natural frequency of the posts as much as possible relative to one another. It will be best not to add too much mass. So I shall use 2x4s rather than anything heftier, like 4x4s.

Or even a nice bit of 4 x 1.25" larch bolted with 12mm [½"] coach screws and load spreading washers. I added a hint of tension between the posts to help to damp the fundamental resonance. The height of the brace was critical to avoid my toes hitting it as I climbed the ladder.

I shall add further cross braces just below obs. floor level and well above head height on the other three sides of the pyramid.

Click on any image for an enlargement.

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