Okay, my last posting isn't even cold yet and I need to write a bit more about the butterfly fastenings we are using. Today my teacher put three huundu in the seam aft where the two side planks come together. As an aside, he told me that this bit of design is one of his signatures. I guess in other sabani the bottom timbers run all the way to the base of the transom, but when we bent the planking we pinched the side planks together over about a 16 inch seam aft. It is kind of sexy to create that narrow edge under the boat aft....
The photo above shows the fastenings and pot of oil that Shimojo san dips the huundu in before hammering them home.
Here's a look at that seam. At the bottom of the photo you can see the base of the transom (an inverted triangle). Two of the huundu have been installed and the mortise for the final one has been cut. Note how the outer edges of the huundu are right at the edge of the planking, which is falling away at a sharp angle. Shimojo san stressed that the width of the mortise needs to be generous (not a gap, but not tight either) otherwise the fastening will split the plank.
But the really important thing is that the undercut of the mortise, which makes the huundu tight, does NOT run from the outer corners to the waist like on our other huundu. Instead it starts from the middle of the sloping side and runs to the waist. So in effect these huundu don't have quite the squeezing power, but this ensures that they don't stress the edge of the plank and split them. These are the details that make my mind race (and sometimes tax my Japanese) when I am doing this kind of research.
I also forgot to mention in my last blog posting that you chamfer all the edges of the huundu in order to help it get started in the mortise. We use a knife or a chisel and just quickly chamfer all the edges.
Once again we used bamboo nails with the huundu. Note how the two enter from alternate sides. They get oiled as well and then all the fastenings get cut flush.
A shot of a bamboo nail with the shaku scale. It is seven sun, three bu long, just under nine inches. The node section in the bamboo creates the "head" of the nail. It is mosodake (moso bamboo) from the mainland. Shimojo san says that Okinawan bamboo is poor quality.
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