A reader asked if I had video of someone using the nail chisel and I can dig around for that (I've been meaning to get a YouTube channel up but I still need to digitize a lot of research video). I post the video below at my Instagram page where it received 10,000 hits. I hope this works posting it here in the blog.
This shows my most recent teacher in Gifu, Japan driving a nail in the bottom of our cormorant fishing boat. Note that he runs the nail through his mouth, something he insisted we do for each nail (900 in all). He claims this gives the nail a better grip in the hole, because the wet nail grabs the sawdust.
Of more interest is the percussive method he uses to drive the nail. I'd say about a quarter to a third of Japanese boatbuilders do this. Most I have talked to don't have a specific name for this technique, but some craftsmen call it uguisu no tani watari, which means "the bush warbler flits from one side of the valley to the other." This songbird makes multiple nests, and can be heard busily flying about, so the bird's frantic song is being compared to the rapid syncopation of the hammer.
The explanation boatbuilders give for using this technique is that edge-nailing is very risky and its easy to split the plank. So the playing of the nail is a way to control the effort and slowly set the nail. Note here that Nasu san is using a wooden mallet. This greatly reduced the force we could apply to the nail and was a sort of control in itself. I was surprised, frankly, at how little these nails were set relative to my previous experience in Japan. Also, the nails fetch up very quickly. You really are not driving them through the wood to any great degree. Again, it would be easy to split the material so careful setting of the nails is crucial.
I should add when there is a crowd this nailing draws a lot of attention, and I have heard other boatbuilders tell me how nailing would attract spectators to their shops. I feel like another reason boatbuilders did this was simply for the sheer fun of it (with 900 nails to drive, why not make it fun?) but no boatbuilder I've talked to will ever admit to that.
