Wednesday, August 5, 2009

First Light XXVI

The past couple of days work on this Japanese garden lantern, the subject of the past zillion posts (this is the 26th of the series), has been quite productive and has seen me through a difficult section of the project. The joinery for attaching the barge board assembly, given the fact that the barge board in this case is a one-piece version of what is normally two or even three pieces, and given my choice to avoid using metal fasteners if at all possible, has been a real head-scratcher at times. I have been problem-solving for this basically right up to the last minute.

Some parts could proceed all the same, despite that fact that not every detail had been established - the main thing was not to paint myself into a corner with a joinery decision that had unforeseen consequences. I had decided that the upper ridgepole, which is the one exposed to view - it could be termed a keshō-munagi - would have a critical structural function and would in fact serve to tie together many of the components in the roof. I wanted the ends of this ridgepole to cog/lap across the top of the barge board miter joint, so I set up a router jig with some MDF and clamps to establish a trench across the top of the miter:


Here's a closer look:


When I was done I had a step-down shelf atop the miters, but still wasn't sure about all the details of the joint yet:


One thing I could do at this stage was fit the upper roof board pairs, which after an initial fit, were first ripped at an angle to establish the top edge:


The rip finished, I trued up the edge with my 54mm kanna:


The board was test fit again so I could scribe the half mortises along the top of the sub-ridgepole:


A few minutes of sawing and chisel work later and the board was fitted:


I repeated the process with its opposite number and at last the roof boards were fitted up:


I left the roof boards at a point - an arris I mean - where they met, with about a 1/16" gap between them so as to allow for some seasonal expansion (or from being rained upon). The upper ridgepole sat atop these boards, which meant that either the arris on the boards had to be trimmed flat to meet the underside of the ridge, or the underside of the ridge had to be cut so as to fit against the arris. I chose the latter route:


The sub-ridge served as a handy paring guide for the rough cut out:


The result of the initial trenching foray:


Now it was time to revisit the matter of the cog/lap joint between the upper ridge and the barge board miters. After a lot of though about it, I decided to take a bit more material out of the upper half section of the barge boards around the miters:


The reader might also note that I have processed a dovetail onto the upper end of each barge board, or hafū. The hafū have also been profiled on top and a small abutment formed at their upper ends - these will be housed into the ridgepole. I omitted to take pictures of these steps as I was somewhat engrossed in the process.

Here's another view of the miter's new slimmed-down look - um, quite a fashion statement:


The housings were then formed on the ends of the upper ridgepole, and the dovetail mortises cut. Once those cuts were tidy, it was time to try a fitting:


The joint seemed like something out the "The Three Bears" children's story- not too tight, not too loose, just right:


Next time I'll show how this turned out - that's my 15 pictures for today. I hope to see you down the line at post 27 - keep your tools sharp.

3 comments:

  1. Hi Chris

    The lantern is really coming together nicely, your joinery skills and attention to detail is always impressive. Speaking of joinery, once the lantern is completed could you perhaps go into further detail on how you decide what joint to use for a given connection and why. Also how we can apply the joinery showed to us in the book (The Complete Japanese Joinery) to smaller scale projects and furniture. For example, how did you come to choose the joinery for the mitered corners of the vanity? I know some of this may have been covered but your knowledge of joinery both with furniture and timber frame fascinates me and I would like to learn more about Japanese joinery and how it can be used to take the place of more common western joinery so many tend to use.

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  2. I have often wondered the same thing as I have been looking at Chris's work for over three years now. I remember seeing the doctor's desk for the first time several years ago when it was online for the first time and being amazed at how he used the joinery I had seen in house building to put together chairs and such. I just wish we could all get together for a class someday and spend a week or so 12 hours a day to just get the fundementals.

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  3. Thanks for the comments gentlemen, and I will give your requests for more information on the 'hows and whys' of choosing joinery some further thought.
    What I can say in the short term is that, historically-speaking, architecture precedes furniture, and thus the development of joinery used in buildings proceeded ahead of the joinery used in furniture. Therefore, joinery used in furniture likely derived from architectural examples and types. Not to say that there aren't joints used in furniture, and developed specifically for it, that you won't see used in building timber frames, and vice-versa.

    One more point - the book "The Complete Japanese Joinery", partly by Nakahara, is hardly a complete survey. In fact, compared to the original text, the anglicized version of Nakahara's book is missing two chapters and has quite a few typographical errors, some of which relate to numbers and proportions. That book is but a general survey I'm afraid, lovely as it is. i realize that it is one of the very few English books on Japanese carpentry techniques.

    I had been thinking of offering a course in the fundamentals of Japanese joinery at some point, but after the very lukewarm response to my offers to teach that I've been experiencing on the US East Coast I've put such thoughts pretty much on the back burner and chosen to focus on other things.

    Well, if it seems there might be more interest in such a course, I would be very open to doing it - thanks for expressing the idea Charlie.

    ~Chris

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