Wednesday, October 14, 2009

Gunwales and inwales

I've come to accept that almost every step in the boatbuilding process takes twice as long as you estimate it will. Putting the gunwales and inwales on Ravn was the exception -- it took about 10 times as long.

Part of it was that I chose to use purple heart for the job. I had some nice 12-foot long strips left over from laminating the keel. I've also come to like the wood for how strong and hard it is. It also glues well. The downsides to the wood are that it does not work well with planes, chisels and spokeshaves because it tears out easily, it gives you the nastiest splinters of any wood I've ever worked with and it smells like -- I'm not sure what -- wet dog, maybe? It's pretty much on the other end of the spectrum from the wonderful pine scent many people associate with woodworking. Another feature of purple heart is that it doesn't take a set. This makes it a favorite of recurve and longbow makers who like to use purple heart to laminate the limbs of their bows, lots of spring and not a lot of memory in the wood. I think that will be a good thing in the long run, but it caused some drama during the installation of the gunwales.

I found out just how springy purple heart is after gluing the two sections of the port side gunnel to Ravn. I let the epoxy cure for a couple of days before I took the clamps (all 64 of them). Just as I stepped back to admire my work, "POP!" "Crack!" "BAM!" Starting from the stern, the gunwale broke loose and lunged at me. It hit the tablesaw instead and I was spared. The noise was loud enough that my wife opened the garage door to see what happened and if I was OK. I stood there in stunned silence and shook my head. I went in the house and didn't return to the shop for a couple of days.

I made a couple rookie mistakes gluing the gunwale. First, and most important, I didn't rough up the surface of the hull or the wood. The hull had two coats of epoxy on it and was real smooth. The second mistake I made was to glue using epoxy only with no additive in it. These were both things that I knew, I just didn't think about them. I was too busy cutting the complex bevels at the bow and stern ends of the gunwale and then measuring and marking the scarf in the middle. It's very exacting work that requires you to clamp, measure, cut, reclamp, mark, unclamp, refine the cut, then finally glue up. I was so focused on getting all the cuts right I totally forgot what I knew about making a good epoxy glue up.

When I returned to the shop I roughed up all the mating surfaces with 60-grit sand paper, mixed in the best adhesive filler I know of (colloidal silica one-to-one by volume) and clamped it up. I also decided to add six quarter-inch galvanized carriage bolts to each side of the boat. I had galvanized carriage bolts on the gunwale of my Chamberlain dory and they did a fine job for all the years I had the boat and will serve for many more decades I'm sure. The thing I want to avoid on this boat is any stainless steel. I'm not a fan. Give me galvanized iron or silicon bronze every time! Until the inwales were in place so I could through-bolt them to the gunwales, I always kept a few strategically-placed clamps on the gunwale just in case.

The inwales were laminated in three-eighth-inch strips: two laminates in the spaces between the frames and two inside the frame heads. I notched the top of the oak frame heads for the two inner laminates. It made for a strong, stiff structure on the sheer. Since I will mount the kabes for the oars, the shrouds and mast bench for the mast, and rope traveler for the main sheet on the inwales, they will need to be strong .

1 comment:

  1. Brandon,

    I just came across your blog and found it of great interest. It appears you may be in the NW, in PSA?

    I am building a Faering, Elf, of Iain O's design. Assuming you are reasonably close to Bainbridge Island, I would like to drop by and see your work up close and personal.

    BTW, I had a similar experience with purple heart. In my case, I attempted to laminate up the frames. If we get together, I'll have to tell you the story.


    T. Eastgard
    tom at eastgard dot org