Monday, July 13, 2009

First Light XIII

Next along the path of many steps that is this lantern project, after shaping the lantern head posts, I set to work forming the tenons. As you may recall, I oriented the mortises in the dodai at a 45˚ angle so as to allow for as wide a tenon as possible - - and allow the tenon to be pegged in place, the pegs also running on a 45˚ angle through the lap.

So, on with hte tenons. First I laid out and then cut to the shoulders:


Both sides roughed out now:


Being perversely inconsistent at times, I cut this one in a different order, cutting the cheeks on the long side first:


Well, I omitted to use my camera for a spell, so the next shot I have is of the four posts test fit into the dodai:


Here's a close up of the meeting between post and dodai corner lap:


I then decided it was time to tackle the floor pan before moving any further upward in the build sequence. I sawed out a piece of mahogany about 0.375" thick, used the digimatic calipers and square to get it as square and correctly dimensioned as I could, and then commenced layout. The first matter of cut out were the mortises for the tie bars:


The mortises were squared up with a chisel, and then I ploughed a dado along the underside, which in turn mounts atop the middle support beam:


I did a trial fit of the floor pan dado to the middle support beam:


Here's another view:


The fit was nice and snug, but not so tight as to cause the pan to bow.

Next I checked the fit of the floor panel in between two of the dodai while locating on the central support beam/dado:


Given that the dodai are joined with lap joints, I had to use a rebate on the two lower pieces of sill, and then tongue and groove the floor pan to the two pieces that lock down the sill assembly:


I processed the rebates, laps, and t&g joinery on my router table. If I had used rebates all around, there is some possibility down the line that the floor piece could warp and curl up from the dodai. Now, given that the floor piece is of edge grain orientation, the chances for any cupping to occur are admittedly slight, but I wanted to also be sure of sealing up any possible gaps so as to make the lantern housing as light tight as possible - I want the light to come out the shoji-faced openings only, not bleed out anywhere else. If it is light-tight, it will also be insect-tight, it seems to me.

All that remained was to slide the pieces down to make sure everything fit up acceptably - here the pan is almost all the way on into place:


Now the floor pan is fully seated into place:


One unfortunate consequence of the joinery decisions here, some of which were figured out as I went along, is that the inner corners of the dodai now have a slight triangular gap as a result of the meeting between t&g and rebate:


This gap, though a bit annoying, is structurally irrelevant and hidden inside the lantern housing - in fact there is some consolation that the corner post conceals most of the opening:



Still, it's a a useful lesson learned with this prototype - on the next lantern I will design this area little differently, which means either making the post and dodai the same size so that the post will cover the gap, or, even better, cut the inside faces of the dodai at the top 0.125" so the abutment is squared rather than mitered.

The floor now needs a hole in it for the electrical cable to come through, and I am still mulling over the details for this, trying to sort it as cleanly as I can. I want to mount the light bulb from the top of the housing, so I will need to find a way to bring the cable up to the top.

In the next installment in this series I will make the 'wall plate' (keta) to surmount the four posts of the lantern head and tie the assembly together. Stay tuned.

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