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.