Building a Tenma-Zukuri Chabune (伝間造茶船) – Part 4

Uwakoberi, Koberi, and Iron Nails

So, with the koberi in place, I added the small deck at the bow and the ōtoko at the stern. I’m trying to find out the term for these small decks, which are more like steps. On the Hozugawa boats, the small deck at the bow is called omote-amaose. But, that’s an entirely different region, so I expect the term in Tokyo/Edo would be something quite different.

I also added the uwakoberi, which is what in the west, one would refer to as the gunwale or caprail. Each was made from a single piece of wood, wide enough to cover the edges of the hull planking and rub rail. I made mine a little wider, so that there is a slight overhang on the inboard side.

On tenmasen, the uwakoberi could be quite wide, serving as a walkway for the boatmen. I wanted to keep true to the Funakagami print, so I didn’t go too wide on this. Also, I had a hard enough time putting a bend in the wood. Any wider would have just made this task more difficult.

One nice thing about the uwakoberi is that it covers the joint where the beams fit into the hull planks. This simplifies things and allows less elaborate joinery.

The next step was to add the nail ends to the inside of the hull. This feature isn’t shown in the Funakagami print, but would have to be on the actual boat. I included the nail positions on my drawings, but I decided to follow what Douglas Brooks and his teacher did on their Tenmasen, which model maker Kouichi Ohata also did on his model. This was to save on nails and work by only having nails in alternating morsises.

I decided to simulate the nail ends by using my vinyl cutter. It’s a little on the two-dimensional side, but at this scale I think it works okay. I began by drilling holes through the mortises to help me locate the proper position for the nail ends.

One of the reasons I ended up putting the “nails” in every other mortise was because of the position of the beam ends. I tried to set up the drawings so they wouldn’t interfere with each other, but things got kind of close in places. It didn’t help that I ended up putting in thick upper beams. They really should have been thinner.

In any case, I created the artwork for the nails using the Silhouette Studio software and cut black, permanent adhesive-backed vinyl on the Silhouette 3 (apparently, there is a brand new model 4 machine that just came out) and applied them one-by-one over the holes I drilled.

Adding the simulated iron nail ends to the inner hull.

I also finished and added the great beam, or ōtoko, to the stern end. Unfortunately, I don’t have any photos of the ōtoko construction. The only thing special about it is the drilling out of the rudder hole, which has to be fairly close to the back edge of the piece, so that the back edge could be cut open.

In actual practice, the rudder assembly would be dropped down into this hole. A pin in the rudder post keeps it from dropping too far. I don’t know the details, but I believe the only purpose of a rudder on this boat is to help keep it tracking straight when propelling with poles. Which means the rudder would have to be wedged into place.

I’ve been thinking that the pin that’s usually in the rudder post, would be removed, allowing the post to drop down a little and wedge itself slightly. I don’t have a plan to add a rudder at this time, but it is a feature that I’ve questioned many knowledgeable people about.

Next time, I’ll be dealing with the decks at the bow and the stern as well as the coppering detail.

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