Monday, September 7, 2009

First Light XLII

This is the 42nd post in a series on the design and construction of a Japanese free-standing garden lantern. For those new to this blog, previous installments in this thread can be found archived to the right of the page.

With the lantern now disassembled completely, I can work on a myriad of minor tasks that have been waiting for me. The post, composed of 4 interlocked sections, is now exposed for the world to see its tender insides:


The first of these details in regards to the post, is completing the wire chase up the middle - here's one completed half:


Here's the mating piece, viewed from the bottom end:


After the chase was done, I finished trimming the mortises for the 4 sets of opposed locking wedges which fix the post sections to one another (not pictured).

The next matter needing attending attention was the mortises for the threaded rod hold-downs - the mortises allow me to place washers and lock-nut atop to the threaded rod and bolt the post firmly down to the foundation. First of course I laid it out:


The side lines were knifed with one of my kama-kebiki:


Once defined, the hole could be bored out and trimmed to the marks:


Then it was time to bore the holes up through the post and into the mortises:


I say mortises since this 4-section post is to be fixed by two diagonally-opposed all-thread rods (Canadians, at least where I'm from, would call the all-thread 'Redi-Rod®'). I think this double-rod connection should prove to be a stouter approach than the usual single rod - and of course it allows me to route the electrical right up the middle of the post, which is the main reason I did it.

The mortises and so forth complete, I painted the end grain exposed inside:


When the lantern post is actually bolted down for good, the open mortise will be plugged by a wood patch that will be planed flush with the surface and will thus keep the elements out of the hole and disguise the connection. You might notice that the hole I have bored inside the post for the all-thread is a little larger than one might expect. I am actually using only 5/16" metal threaded rod, so what gives?

Answer: I'm trying out a new idea here - I have drilled the hole larger so that I can insert a plastic sleeve to line the hole. You see, the problem with using metal fasteners in outside locations is that the temperature cycles, day to night, create swings which promote moisture formation. Since metal conducts heat much more readily than wood, it has a lower effective condensation point and thus metal always gathers moisture around it more readily than wood. What this means is that the moisture accumulated then is often soaked up by the surrounding wood, and if not allowed to easily evaporate will promote rot. Look at any nailed wooden fence for example, and you will see the first points of failure are always around the metal fasteners. For this reason, I try my utmost to limit the use of metal in those parts of wooden structures which are exposed to the weather. In some cases, like the attachment of this lantern to its foundation, it is nearly unavoidable to use some metal, so my idea is to line the rod hole with a 0.5" pvc sleeve so that moisture accumulating around the all-thread rod will not be able to pass over to the wood. This is also why I go to the trouble of painting the end grain inside the mortise and why I will employ a plastic washer under the metal washers when it comes time to fasten it down. I don't know how much of a difference it will make in the end, this being an experiment I will need to wait 20 years to see the results of, however I don't see any disadvantages to the method either, other than a slight bit more time and a couple of dollars for the plastic tube, so I'm giving it a go.

With the hold down mortising complete, I re-assembled the post and made a paper template, via a pencil rubbing, of the three holes in the post bottom:


This template should come in handy when it comes time to drill the three holes into the foundation stone in another day or two.

In other news, I have glued up the first of the lattice frames for the lantern housing:


The glass fits, BUT the glass cutter did not cut the panels totally accurately to my template and the glass is nearly 1/16" too long in one dimension. This is causing a slight problem. After the holiday weekend is over I will call them and see what can be done. I don't expect they can score and break off 1/16" of glass, but I'm hoping they could do a 1/8" trim, which would work for the frames as they are set up. If not, I have to deepen the lower frame slot to allow the glass to slide a little further down.

And finally, for today, here's a look at the nice pile of parts with their freshly-painted end grain:


The remaining work to tackle, besides drilling the rock, comprises making various pins and wedges, along with final planing and chamfering of the various pieces. The post will have a chamfer about o.25" across, maybe a tad more, and the other parts will have a minimal chamfer no greater than 0.0625" (1/16"/ 1mm)).

Thanks for taking a look today - hope to see you next time for post 43 in this set.

3 comments:

  1. Hi Chris,

    With only a sixteenth of an inch of glass to remove, it can be done by grinding with a coarse stone (stain glass artisans have to do it all the time to smooth slightly off or jagged edges). I don't know how successfully it can be done with a machine grinder (anything's possible) - maybe someone out there has experience doing it that way. Anyway, a possible other option.

    Great project, great work and an enjoyable read.

    Steve

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  2. Well, thank you gentlemen. I don't have any sanding equipment myself, however it was no problem as I took the glass back to the glaziers and they trimmed the 1/16" off with a wet sanding machine of some sort. No charge charge of course. I asked the man behind the counter about using a waterstone to make adjustments and he said that would work fine.

    ~Chris

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