Visiting the Anderson Japanese Gardens has been on my to-do list for some time and since it’s only a couple-hour drive from home, this summer seemed like a good opportunity. As would luck would have it, Douglas Brooks was slated to give a short afternoon workshop and evening lecture at the Gardens last Thursday and so it would seem like the perfect storm had arrived.
For the afternoon workshop, Mr. Brooks gave a two hour demonstration on how the planks of one type of traditional Japanese boat were edge-joined. In this case he was replicating the joints used on the tenmasen canal cargo boat that he built for the Gardens a couple years back.
A caveat: this entire process is new and quite unfamiliar to me and so my description is only as accurate (or inaccurate) as I can remember it. To really learn how this process works, you would be advised to acquire Mr. Brooks’s new book, Japanese Wooden Boatbuilding.
To begin the process, the first two planks needed to be prepped to be nailed together and that meant creating a perfectly tight edge joint. The method to do this was one I had never seen. It starts with stabilizing the two planks by wedging the four poles you see below between the ceiling and the planks which are then resting on floor sawhorses. Mr. Brooks, using a hammer, lightly tapped the planks together and then began ripping a “kerf” between the two using a typical ripping motion. He then traversed the slot between the planks back and forth several times, allowing the folks in the class to have a try. For the last pass or two, using the rip saw in a horizontal sliding motion he essentially rubbed out the angled saw marks from the previous passes creating horizontal saw marks on the edges of the planks.
After the final pass with the rip saw a hammer was used to pound a concave shape along the entire edge creating something of a “U” shape so that when the boards are joined together the 4 remaining points of the two “U” shapes compress and when submerged in water the hollows expand back up to their original shape creating an extraordinarily tight seal. Watertight you might say.
Note the way the board is wedged and subsequently stabilized into the floor horse. Reminds me of the compression joint in traditional Japanese sawhorses.
Once the edge work is complete, notches in one plank are chopped out to eventually accept the curved nail that will hold the planks together.
Here are the notch keys that will be wedged into the mortise after the boards have been nailed together to cover up and seal the nail and mortise.
Before driving the nail a pilot hole of sorts is chopped out of the 1st plank to accept the nail. If you look closely at the chisel being used you will see that there is something of a cross guard where the tang enters the handle. This is to facilitate the use of the hammer in pounding the chisel back out of the mortise, essentially performing the reverse operation of pounding the chisel into the mortise. In effect the chisel resembled a small sword.
For the other plank, the chisel was driven into the corresponding hole which rather than create a receiving mortise simply compressed the wood into something of a “pilot” mortise to make room for the nail and which would then swell back out, clamping the nail, once exposed to water.
After the planks were nailed together and the covering wedges placed, Mr. Brooks used a Japanese adze to trim the wedges flush with the planks-this is delicate work to say the least. This was the end of the workshop portion of the day (about 2 hours). But it was a lot to take in, even in that short amount of time.
A few pictures of the nails used (which were hammered into curved nails prior to nailing the planks together and a few of the chisels used, including a curved chisel at the bottom for creating the pilot mortise mentioned earlier.