Wednesday, July 29, 2009

First Light XXII

In today's post I will show how I took the hafū, which I rough-cut out and trimmed to shape last time, further into their more nearly complete form, short of the joinery. I've spent much time puzzling over the best way to attach the hafū boards to each other and, simultaneously to the ends of the keta and the munagi. There are several ways to do it - beyond the obvious method of spiking or screwing them into place, which are not under consideration here - or using threaded rods to pull things together (also not under consideration) there a couple (or three) all-wood joinery methods. These methods basically devolve into two types:

1) the hafū attach by dropping vertically into place on male dovetails on the keta.
2) the hafū attach by moving horizontally onto stub tenons on the keta and munagi, using various types of locking keys to pull them into place.

I'm going with my own version of method (2) above, with a few elaborations. We'll see how it turns out, as the prototyping continues.

Okay, after I had my four pieces of hafū roughed out, and the lines transferred to them from the templates, I proceeded to give the router a good workout, working out on my sawhorse set up in the yard (trying to keep the dust in the kitchen down a little bit).

First off, I processed some slots on the backside of each board, which define the position of the two roofing boards:

Here's a more close up look at the slots on the two boards on the right side of the above picture:


Next I processed a couple more slots on the backside of the boards, but these aren't actually slots as such, they merely define a raised platform which will abut the underside of the roof boards. This platform will help to guard against any tendency the quarter-sawn boards might have, in the sun, to cup. Wedges will help this process as will soon be apparent. This detail should make more sense as the pictures roll out in this build:


Then with a change to a shorter bit, I free-handed the router and removed a good swath of waste material from the back, taking the cut close to the edge so the router could remain supported while cutting:


Also note that the board support ledges on the lower side have been shortened to about 2" in length - I don't want these ledges to be visible at the end view of the boards.

A closer view:


And yet closer:


An electron-microscopic view of the fiber:

(just kidding!)

Next I turned to the opposite (face) side of the boards and processed the waste out, leaving me this pile of rubble:


Then I sawed the edge remains of the cut portions off, and out came the hand plane (and, oh yes, off with the earplugs!) to clean the edge up a bit:


Figuring was on to a good thing, I decided to trim the lower end of each hafū to the line:


The finish was acceptable:


Time for the always controversial show, a definite thrill-a-minute, yes, it's Sawing for Teens!:


As these boards are representing two separate parts, one atop the other, the cut is to define the lower board, the actual hafū-ita, which is set back a short distance from the end of the cap above.

Following the sawing, I did a little paring:


And this is how it looked after the chips had settled:


Now, on the uphill end of the boards, I needed to trim the board support piece back a bit to fit onto a notch which will be made on each side of the each end of the munagi (ridgepole). This I did by chopping and paring:


The result:


Well, that's the 15 pictures I wanted to post today - more to come! On to post 23

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