There are a several kits available to the wasen modeler, between Woody Joe and Thermal Studio, but if you want to scratch build something unique, you’re going to have an extremely difficult time. Japanese boat builders didn’t draw detailed plans the way western boat builders did, and pretty much all that is available are those created from a study of an existing boat type.
However, there is one fairly accessible set of drawings of Japanese watercraft that was made in the 1880s and published in a set of books called La Souvenirs de Marine by French Vice-Admiral François-Edmond Paris. This set of large-format books has seen a number of re-prints, and I’m not sure what the date is on the most recent reprint. But, there should be copies accessible in most of the larger library collections, and used copies can be found on Amazon and other booksellers, with prices that vary greatly depending on edition and condition.
Drawings included are of ships from across the globe, and the text is in French, but this collection contains some of the few contemporary records of traditional Japanese watercraft available. Of the sections I’ve collected from the books, one illustration plate shows four different riverboats of various types. Other plates show two examples of bezaisen, or coastal transports. Other plates show a couple examples of highly ornate row galleys, one of which bears the crest of the Chiba clan on it’s large squaresail.
I haven’t studied these drawings in too much detail except for the two sets of bezaisen drawings, which are specifically of what appear to be northern port coastal transports, or Kitamaebune. The text doesn’t mention any Japanese terms, and again, it’s all in French. But the drawings are fairly well detailed. And, I suspect the text doesn’t give a huge amount of detail about the watercraft as it’s mostly limited to labels and sidebars.
Now, that I look at it more closely, I’m seeing how I might be able to model some of the other boats illustrated in the books, so I’m finding myself more interested in learning about them. If I find out more, I’ll post about them here.
There are a couple of paperback books of selected plates that were published by James E. Hitchcock, which you can find on Amazon.com for less than $10. While the images are scanned and reprinted from an original copy, and the French text is very difficult to read, the book provides a handy reference so you can determine which plates you may be interested in.
I have found that the San Francisco Maritime Research Center has the set of books available, and will scan whatever figures you need and will email them to you at your request at no cost. You can contact them for details at 415-561-7030 or email them through the Park’s website.