Building the Octagon P.47 The pier gets a mini skirt.

Later again I brought a sheet of 1/2" plywood home and cut cross braces for the pier to fit just below the obs. floor. I wanted to maintain plenty of headroom [2m or 6'6"] which rather limited what could be done.  After fixing the 60cm [2' high] tapered panels to three sides I was unable to detect any change to a thump on the bare posts.

Perhaps I am simply confusing natural resonance with stiffness? Unless the posts are "excited" by being struck they simply do not vibrate. Wind is not an issue in an enclosed building. So where will any physical "excitement" come from? The drive motors? It seems unlikely that they could vibrate enough to shake the massive mounting and pier once a slew is concluded. The building is isolated from the pier. There is two feet of sand and gravel between the footings for the building and the pier. 

I really need much better and longer screws for fixing this cladding. Pre-drilling might help to pull the cladding down really tight. My thinking is that CSK heads will not hold as well as something with a flat surface under the head. Only friction between the cladding and 4x4 pier posts can damp vibrations. The screws I have been using actually push the cladding away from the posts as I am seeing lots of daylight between post and plywood. Perhaps the screws need long, plain shanks to stop acting as differential jacks on the harder plywood? I could use a construction adhesive between the pyramid's posts and the cladding but would need to be sure of a guaranteed close fit before the "glue" stuck fast.

Fed up with the wide gaps, so I pulled all the [joist hanger] Paslode screws out and replaced them with standard 40mm Torx wood screws. These pulled in really tight and provided the grip I badly needed.

These Paslode screws are dreadful things! They are almost impossible to drive in because the sharp point is completely smooth. There is no cutting edge to start digging the screw hole. The Paslode screw shanks are meant to match the holes in reinforcing, hole plates or joist hangers. But! Being so difficult to start these screws the ground below is often littered with fallen screws!

Paslode should really decide whether they are offering screws or nails. They may need a hammer [or hammer drill] to get them started but should it need taking two tools to the job? If their screws don't go in perfectly straight on the joists hangers they regularly jam in the holes! Having screws instead of ring-shanked nails is certainly worthwhile but why no self-tapping, nose profile?

I have often spun these screws for half a minute, pressing hard into soft, sawn timber without the least penetration! The screw shank has to be steadied with a spare hand every single time. The Torx socket is too shallow to align the screw safely on the driver tip. So the screw immediately leans sideways and the tip of the driver falls out more often than not. Resulting in the tip of the driver digging straight into the pristine wood surface! Perhaps Paslode screws really do need a hammer drill to get them started?

When you do finally get a Paslode screw fully in, it grabs the Torx driver bit out of the magnetic extension and throws the bit away into the colour-matched gravel! Almost every time! How is that even possible? Too loose to hold the screw straight on the driver bit [for one hand fixing] but won't let go of the screw afterwards. I have tried stabbing the screw point into the wood with the full weight of my DeWalt drill/driver behind it but it really doesn't help. How do you freehand stab through a hole in a connector plate or joist hanger? It can't be done!

Avoid these Paslode screws like the plague! They have driven me nearly mad! I am so cross I am sorely tempted to post a negative video on YT. They aren't cheap either. I paid £14 equivalent for a box of 250.

Something else to avoid: The completely Moto-Gutless DeWalt DCD771 rechargeable, drill/driver. Even on a maximum torque setting of '15½' and Low Speed '1' it can't even manage a 2" Torx wood screw. So it has to be used in "Drilling" mode for every single job. So you are immediately set up for hand injuries and damaged work and screws.  

Battery life is pathetically short as well. But then, it seems DeWalt is owned by Black & Decker. Labelled down to a price in China. Not up to a quality. My Bosch batteries and tools have proven to be far superior and longer lasting.

After all the Paslode screws were replaced with ordinary Torx screws the pier resonance dropped to about a half of the previous two seconds. Now I have run out of 40mm Torx screws and must get more to finish the job properly. I can use them on the top [obs.] section of plywood cladding as well. Perhaps with further improvements in resonance behavior? What's better than 40mm Torx screws? 80mm Torx wood screws! Lots of them! They really know how to pull the plywood down hard onto the wood! So, let that be a lesson to you!

With the plywood skirt now firmly attached I decided to add a trim to kill self-resonance in the unsupported plywood. I used exterior white wood glue and lots of clamps after carefully mitering the 4" wide slats. I had no desire to add more mass near the middle of the pyramid of the pier posts. I shall check tomorrow when the clamps come off whether the damping time is shorter than before adding the trim.

BTW. The [powder] sachets of Safe-Way, water-based, timber protection has arrived but now matched by a forecast of two days of rain! With a two hour drying time I had better put off painting until it is forecast to be dry for a while. Otherwise most of it will probably end up on the ground. Instead of where it should be soaking deep into the timber. Chelating mordant to you too, Matey!

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