I will conclude the subject of yesterday’s post, which was the fabrication of the lower draw bar and sliding dovetail key joints which fix the lower ends of the hafū to the edge of the lower roof boards. After the bars and keys were complete, I next cut the sliding dovetail mortises to receive the ends of the draw bars:
After rough cut out, all that remained was to trim the fit of the walls of the dovetail mortise:
Then it was time to fit the joint up – first the draw bar slides into position:
Then the sliding dovetail key is started:
A few fine adjustments are made so the joint has the right amount of tension pulling together.
Now, it so happened that I had to make some fitting adjustments to the a couple of days later, and this resulted in a shift of position of the hafū relative to the lower roof boards. This meant that my draw bar mortises were slightly offset and the joints were spoiled. Ooops!
I thought it would be worth showing how I dealt with this problem, since these sorts of things happen once in a while. First I chopped the mortise out to accept the patch:
Then I sawed out the patch from a piece of scrap:
This rough piece I then trimmed with a chisel to get it clean and square, and then fitted it to the mortise.
Next, out came the glue and in went the patch:
That was followed up with some chisel paring to clean the excess off:
This one didn’t have the best grain match, however it is also concealed behind the edge of the lower roof board, so that didn’t matter too much. After the glue was dry, I re-marked out and re-cut the sliding dovetail mortise.
Another step relating to wedges are the ones that slide down through the sub-ridge and draw the upper bars tight, thus securing the miter of the tight to the end of the ridge:
The sliding wedges fitted to the ends of the sub-ridge are in turn covered over by the top ridge. Well, I call it a ridge, but in reality it is a decorative element simulating a tile ridge atop the roof. A decorative element, yes – all the same it does much, in the manner I designed it, to strengthen the interconnection of the key roof parts.
There are yet other wedges – some readers may recall the way I cut the back of the hafū to accept the roof boards. The lower most boards are to fit up against a wall on the hafū, and they are to be wedged up tight. This called for half-dovetailed tapered sliding keys:
The sliding keys are offered up and then adjusted as neccessary to get a good fit:
This one is 95% of the way in, I save a final adjustment for after final planing:
That’s all for today – see you next time at post 34.