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Sasabune: Hiroshima Riverboat

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Figure 1. View of the sasabune stern. Note how the lower hull planks extend slightly below the base of the boat. Exposed
fasteners are visible along the base of the transom and hull planking. Photo by Michelle Damian.

Even today in certain parts of Japan, people still use wooden boats to transport people and goods along the rivers far inland. The art of building these vessels is dying out, as in many cases there are no manuals or written instructions and fewer young apprentices. Before his death, I interviewed Mr. Mitsumori Kanji of Miyoshi (Hiroshima prefecture) about a type of riverboat that he had built countless times. With its pointed stem, elongated body, and blunt stern, the sasabune, named for the bamboo leaf that it resembles, can maneuver relatively easily even in the shallower river waters.

Construction of the sasabune is deceptively simple. Two planks (strakes) form the base of the vessel, and two strakes on each side form the hull topped by a sheer strake (a thinner piece of wood that forms the edge of the hull). With two passengers in the boat, the lowest strake would be submerged below the water. The lower hull strakes overlap the base slightly, serving as protection for the boat bottom (Figure 1). If the water becomes too shallow and the boat hits the riverbed, the base of the boat will not have immediate damage. At the bow, a stempost meets the base planks (Figure 2), and a single piece of wood forms the transom for the stern (Figure 1). Pairs of deck beams traverse the boat at the bow, stern, and midships to provide additional structural reinforcement.

Figure 2 Side view of the sasabune bow, showing the hull planks meeting the stempost. Photo by Michelle Damian.

Less obvious are the joinery and fasteners (nails) that help make the boat watertight. To ensure that the strakes meet one another with as little a gap as possible, the shipwright places them together side by side and uses a special saw with jagged teeth sawing along the edges of the two pieces of wood in a particular pulling-type motion. Creating those edges and grooves helps the strakes fit together perfectly. Fasteners are inserted by first chiseling a hole for them to slide through easily. Flathead fasteners are used in places that are more likely to require future repairs as they would be easier to grab onto for removal. Fasteners without such heads are used in more stable points. Larger vessels might have wooden plugs to cap the fastener holes and create a smoother surface, but the sasabune fasteners are left uncapped and exposed. Poles are usually used to help propel the boat downriver, and it is towed back upriver after the journey’s end.

The AAS Secretariat is closed on Monday, July 4, 2022, in observance of the Fourth of July holiday.