Building the Octagon Pt.39. Plywood cladding the pier.

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Saturday: I saw a sign for a flea market in a village and picked up a secondhand, 1200lb boat winch for about a fiver. 50DKK = £5.85 = $7.65US. Now I can make the hatch as heavy as I like and still be able to lift it. If only I can work out how to be in two places at the same time. Hmm. Perhaps I can use it for lifting my heavy mounting up to the observatory and the onto the pier. The chain winch is rather clumsy in comparison, is incredibly noisy, but probably has far better brakes.

It rained on the 18mm plywood sheet on the way home and it went as bent as a banana, but worse. Overnight it had flattened quite a bit but was still curved across the width. So I leaned the sheet up against the shed, convex side out in bright, 70F sunshine. Within a short time it was as flat as one could wish for. I then carried my measurements over to the sheet and marked it out ready for cutting when it cools off later. I had better cut out one piece and see how well it fits on each of the four sides of the pier.

Getting the tapered shapes exactly right for each side is proving a struggle. So I cut the second one oversized and will use the router with an edge trimmer bit to match the edges of all four panels to the 4x4 posts and each other. I used the jigsaw without a fence to follow the line as it is quick, light and fairly effortless. The problem is that the narrow blade wanders. Which is acceptable if I stay outside the cutting line. The wavy edge can then be trimmed back.

Flush trimming router bits have a supportive journal bearing which follows a straight [or curved] surface. The cutter is made to the same diameter as the bearing. So cannot dig in or undercut the guide surface provided the router base remains in contact with the work.

A quick image from the south after I tidied everything away for the night. The north and east [still untrimmed] pier panels are tacked in place with small screws. This was after initial clamping for marking the edges after finding their best relative positions. 

I just want neat joints between the panels for cosmetic reasons. There are other ways to repair a wavy cut line. An angle grinder with coarse abrasive disk or an old fashioned hand plane will both work with care. I may use one or both to take the worst "bumps" out before using the router. Or, one could cheat and cover the ugly corners with an angle profile.

The heavy mounting has been sitting under a tarpaulin since I started the octagon build. In theory I could lift it up and place it on the pier for observation from the raised platform. There is no reason not to do so and just cover the mounting with the same tarpaulin afterwards. The cladding is just extra insurance in strengthening the pier. The dome, or roof, can easily follow later.

From up on the platform I have been watching Jupiter steadily cross the southern sky without so much as a peek though a telescope. The reason being that from the ground it [Jupiter] remains completely invisible behind the house roof. I'm not sure how much of an encumbrance to building work it would be to have the mounting permanently set up. I ought to make the big lift while the western pier panel is still absent to provide maximum clearance at obs. floor level.

I'm still pondering on a suitable 'jib' for the chosen hoist. If I lift the mounting inside the building I could use the pier to get the mounting up to to the obs. floor. Getting it up on the pier is quite another matter. I would have to build a tripod up on the obs. floor for the last few feet of the lift.

Click on any image for an enlargement.

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