Thursday, December 10, 2009
Sandaa and Other Lessons
The two most unwelcome words in Japanese for me are "Sandaa oneigaishimasu," (please give me the sander). Shimojo san is basically limited to working with one hand and so he does an astounding amount of this work with a small electric plane and an angle grinder with a four inch, 80 grit sanding disk. The last two days we have been shaping the inside of the bottom of the boat and after doing the rough work with the electric plane he reached for his sander to finish it. The sander produces clouds of sawdust, and having suffered through the hollowing of the planking I decided to jump in and offer to at least smooth the bottom with one of his old hand planes. Thankfully, he let me go ahead, but still this was followed by four hours of sustained sanding by Shimojo san.
Shimojo san mounted the upright handles on some of his planes to make them a bit easier for him to use one handed, though he said that in the old days Okinawan planes had horizontal handles just like Chinese and South East Asian planes.
I was thinking as I cleaned up that I made a little diorama of Iejima.
This is what we have produced since our first dump run. I've told Shimojo san we have one boat on the sawhorses and two on the floor. He thought that was funny. Today we came in and he told me to start installing huundu along the seams inside the bottom. He looked at my first one and told me I had made a mistake, that I can't leave any gaps around the huundu (you can see the gap along the right side of the bottom edge). He hadn't been so concerned with the other ones I did on the outside of the boat, but then I realized that inside the boat any gaps in these fastenings will let rainwater into the bottom.
So I will review again the process of installing the huundu. No doubt I will learn more details and refinements as time goes on. Remember, I make these mistakes so YOU don't have to!
Shimojo san marks the plank seam so I know where to layout the huundu. The seam is so well fitted it can be hard to see.
He's reminded me more than once to make sure my pencil is sharp when I trace the huundu. Then we use a drill to hog out some material in the center. Shimojo san depends on the depth of the hole (we have a stop on the drill) to gauge how deep the huundu should be mortised (they go in 1-1/8 inches in the bottom).
The first chisel cuts are just to clear out the bulk of the waste in the center. The stain is from the oil that Shimojo san insists I dip the chisel in before working. That is common practice in Japan, though I never see reference to it in the States. Note that the huundu is far from symmetrical. Shimojo san cuts them free hand on the bandsaw, finishing the four angled faces with a sharp chisel. So when you trace them you have to mark them to keep the orientation correct.
My great contribution to Okinawan boat building: I mark the depth of the mortise on the back of my chisel (one inch wide), which I find far easier than searching around for the bottom of the drilled holes.
I chisel further out toward the line, keeping away from the top and bottom edges. This is why I screwed up the other fastening: I got too close too soon and the fragile top and bottom edges, running with the grain, are easy to crush.
I make four chisel cuts (all straight down) and these are at the final locations. Note how the cuts taper from to the line at the corners to just inside the line at the waist. That little bevel is the key to getting the huundu to pull the two planks together. I still don't touch the top and bottom edges.
Time to clean out the waste with the narrow chisel. I try NOT to lever against any of the edges of the mortise, especially the top and bottom.
The final cuts clear the top and bottom working very carefully just to the line.
Before hammering them home we bevel the edges going in to make them easier to insert. This is covered in my earlier two posts on huundu. You may notice that the labels changed in the photographs. I used several to illustrate this lesson.