Friday, July 31, 2009

First Light XXIV

Moving right along with the barge boards and associated joinery here with this garden lantern prototype. Much of the time in this stage of the project I am making small adjustments, frequently refitting and checking, and cutting the joints stage by stage. It's more efficient of course to cut all the parts in one fell swoop ,and then connect all the bits together, however I am venturing into new ground in places here, and feel the need to tread carefully. The more hours one gets into the making of a given piece, the more is at stake, and I don't want to make any gross errors at this stage of the process. It can get a little nerve-wracking at times, and it's helpful to know when to take a breather here and there.

Last time I had completed the stub tenons, or mechi, on the ends of the wall plates and the ridgepole - here's the view from the backside:


Next step was to work on the mechanisms to draw the barge boards - hafū- tight to the beams. My idea here is to use a mechanism that draws the boards in horizontally to the beams. This starts with cutting some short sliding dovetail trenches in the lower ends of the hafū:


Look a little closer and you'll see them:


After these slots were cleaned out a bit, I refitted the hafū so I could transfer the lines from the dovetail slots to the nose of the ridge. Then I laid out the tapered mortises on the ridge pole ends which are to receive the wedges which are involved in the draw mechanism:


After most of the cut out of the wedge-mortises was complete:


Just a little more paring to clean them out remains - which will wait until I have have made the wedges.

Now for the draw bars - I returned to my pile of offcuts and dragged out another little piece of Bloodwood. This was a piece I needed to re-saw (re-taper in other words) on four sides to get the straight grain alignment I was after, followed by the usual jointing squaring and dimensioning by hand plane. Once at dimension, I cut them to length with a 240mm nokogiri, and then trimmed them by chisel, gang-style, to get them all the same length and with square ends:


A little fun with the router table later, the draw bars had their male dovetails cut, and were partially fitted into the barge board mortises cut earlier:


A closer view:


In the above view, the draw bar is only just started into position - another bit of trimming is required yet in the dovetail mortise to get it seated to final position.

A view from the end-grain side of a hafū board, showing the insertion of the draw bar:


Once the draw bards were fitted to a given pair of barge boards, I could check them in an assembled position to be sure that there was an adequate space between the two bars, one of which has been cut at the end to a half-lap (the other to follow shortly):


There's needs to be enough space for the bars to fit in their mortises, plus space allowance for them to move through the seasonal humidity swings.

Here's the slots in cut in the end of the ridge to receive the Bloodwood draw bars:


The draw bars need to be keyed to their slots so that the wedge cannot push them outward. This necessitated, as shown a couple of photos back, a half-lap on the end of each bar, which I processed with a saw cut and some chisel work:


Some scars in the end of my sawhorse cap will need to be dressed out when this project is done.

The slot mortises on the ends of the ridge needed mortises to receive the half-lap extensions of the draw bars. Blind mortises like these are not the easiest to cut cleanly - I start with a brad point drill bit:


It's handy to have a full set of long thin paring chisels sometimes - here my Tasai 6mm gets nosy:


Last one for today - a picture of the trial fitting of the barge board, the draw bar sliding close towards the half-lap mortise, and with the newly cut tapered wedge mortise also clearly visible:


I wonder if this will work?

Until next time then - please stay tuned and of course comments/questions/heckles are always welcome.

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