The Zutta Tenma is a small Tabune, or rice field boat, from Toyama prefecture. My model is based on a drawing that I got from Douglas Brooks, which is very similar to one he used when he built one in 2016.
This drawings varies only slightly from one I used, which I believe was published in a museum book on boats of Toyama prefecture. I managed to find a couple of these books on Yahoo! JAPAN Auctions and used my Buyee.com account to purchase it. This, by the way, is a very useful buying service, which allows you to view products in english and ship them to a Japanese address, where they handle the international shipping for you. It’s very easy to use and gives you access to lots of great stuff for sale in Japan.
Though it’s going to be a week or two before my books arrive, I have all the information I need on building the Zutta Tenma. The following is the drawing I used, which you’ll notice is slightly different from the one used by Douglas Brooks.
Most notable difference I found was the design on the back, which is called a Yago, which is a “house name”, or perhaps in this case, a house symbol. This is apparently something different from a Mon, which is a heraldic symbol.
As for differences in construction, the most significant differences are the use of a separate piece of wood in the hull planking near the prow, and the absence of mortises for attaching the bow planks to the hull bottom on my drawings.
The use of that triangular piece near the bow is a material savings measure, allowing the builder to use a slightly narrower piece of wood to build the hull planks. The absence of mortises, I can’t explain. I would think nails would be needed to secure these parts together. I decided to add them to my own model.
Given the size of the boat, I’m building this at 1/10 scale, which also allows me to use sugi, or Japanese cedar. This wood is too grainy for smaller scale models, but is commonly used by boat builders when modeling their own boats. It also has the advantage of having the right coloring, without resorting to dyes or stains.
As always, I start with a mold – a kind of removable framework that helps me hold everything together at the proper angles. For this I use 1/4″ thick MDF board (Medium Density Fiber).
Again, the hull planking is constructed of sugi, or Japanese cedar, approximately 4mm thick. For the most part, it’s important to cut planks slightly oversized, as they will need to be trimmed to fit.
Dealing with the construction of the bottom, or shiki, is the first construction step of the model itself. For model making purposes, one edge of each plank generally needs to be untouched. The narrow or “pointy” end of the mortises are located a set distance from that edge. On a full-sized boat, nails are driven into the narrow end of the mortise, out the edge, and into the neighboring plank.
The fitting of the bow planks to the bottom took some guesswork and fitting by trial and error. I got the approximate angle of the peak of the two bow planks and temporarily taped them together to figure out how much to cut them to fit the v-shape at the forward end of the bottom planking.
I then cut the bow planks and added the mortises at the bottom ends of them. It was necessary to wait until this point, as the mortises have to be positioned relative to the edge they are used to fasten. The bow planks were then glued together and I pretty well just eyeballed the angle between them and use clamps and rubber bands to hold them together until the glue dried.
Afterwards, I test fit the completed bow planks to the bottom and trimmed the joint between them until it was a good fit. On the full sized boat, a technique called suriawase would have been used whereby a saw was run through the joint, resulting in a more accurate fit.
The most obvious error I made here, which I didn’t realize until later, was that I pre-shaped the tip of the bow, creating the curvature. This is not how it was done on the real boats, but I didn’t realize that at the time, and only discovered later that it would have been better to shape the bow after adding the hull planks.
Next time, I’ll talk about the todate, or transom, and the tana, or hull planks.
You can read more about Douglas Brooks’s 2016 Zutta Tenma project on his blog here: http://blog.douglasbrooksboatbuilding.com/2016/02/the-rice-field-boat.html