Part Two: Buildin’ the Bones
In our last thrilling episode, we had cut and prepared all the frames from 12mm (1/2″) meranti marine plywood, and ripped and scarfed the keel, gunwales and other stringers from 1x pine planks from Lowe’s. Now we were ready to put dem dry bones together. But just so that you can see where we are headed, here is a pic of the (almost) finished product:
The strongback is a simple straight, not-twisted 2×4, cut to 7′-4″ length, mounted to two plastic saw horses with deck screws, to which two end brackets are screwed, to hold the straight, flat, keel in place. Again, there is no rocker in the Chuckanut keel, so after the bow and stern marine ply pieces are screwed on, the keel can be clamped to the strongback. Keel straightness is assured with a chalk line previously snapped on, and small wooden blocks added each side of the keel to keep it from moving around.
The frames are placed on the keel at the specified locations. There are two closed frames forward of the cockpit, one open frame in the cockpit, and two more closed frames at the stern. The stringers land on the bow and stern pieces attached to the keel. For this first boat, I did not soak or steam any of the stringers before mounting them, as I was not sure what that would do to the Titebond III wood glue I had used in the scarf joints. Those dry stringers required a great deal of force to bend around the frames. Had I used epoxy to glue the scarfs, I could have soaked/steamed the stringers before installing, to make the bends less stressful.
Dave Gentry recommends using epoxy as glue throughout the build, and I later purchased from Duckworks two 6.45 oz tubes of System Three Silvertip Gel Magic Epoxy, which comes with mixing tubes, and is much more convenient to use than having to mix and thicken small batches of epoxy as you go. This epoxy is very slow curing, so there are at least 30 minutes of “open time” where the epoxy in the mixing tube will remain usable, and even more time in cooler weather.
The gunwales go on first. Each gunwale is laminated from two 3/4″ square stringers. The bottom parts of each gunwale are fastened to the frames with screws, then glue is applied and the top part of the gunwales are applied, and likewise fastened with screws. Again, I used the Titebond III wood glue to laminate the gunwales. I staggered the scarf joints in each gunwale part, to minimize the stress on those joints. There is considerable force required to make the bends in two planes at once! It will take quite a few clamps to try and get the gunwale laminates aligned both vertically and horizontally, which will be important later when applying the covering.
I happened to have several light one-inch black straps about 4 ft long available, which were essential to hold the stringers in place, especially at the bow and stern ends, unless you have a great many more clamps available than I had. At the ends, I temporarily inserted the occasional small wood screw, just to keep the straps from slipping off the ends of the stringers.
Dave Gentry is also averse to using lashings to attach the stringers to the frames because of the tedium of doing all those lashings, and recommends using the wood screws with a small dab of the System III epoxy instead. I liked the idea of lashing the stringers, so ended up using a system of wood screws, (because of too few clamps to hold everything together), combined with lashings. Great videos about lashings are on Jeff Horton’s Kudzu Kraft and other websites. Pay special attention to the demo on tying the figure-8 stopper knot! Regular knots will not hold in the waxed polyester artificial sinew. I always backed up the very small stopper knot with an upstream couple of granny knots, just to ensure the stopper would not pull through. I obtained the synthetic sinew for the lashings from Hobby Lobby. Also note in the below pic that I used a rat-tail file to notch the gunwales, stringers or keel wherever the lashings were installed where the polyester covering would later go, to avoid any bumps which might become wear points. If you look closely at the middle stringer, you can see the only cracked stringer on the boat, which occurred when I unnecessarily put in a screw after lashing, just because all the other joints had screws! Actually, with the lashings, no screws were needed, and I may not use them in the future.
The build requires only two sizes of stainless steel wood screws: #6×3/4″ (75), and #8×1-1/2″ coarse-thread (60). So I would have plenty for two boats, I ordered two bags of 100 of each from Duckworks, at very reasonable prices. It is absolutely essential to have a counterbore drill with adjustable length, as both the marine ply and the stringers will probably split if they are not pre-drilled for the screws. Actually, I used a #8 counterbore drill for all the screws, just adjusting the drill length as appropriate, and that worked fine. It is also handy to have two drill motors, one with the counterbore drill, and the other with the screwdriver bit. I didn’t have two, so I had to change bits frequently, which slowed things down a bit.
The biggest problem I had on the whole build was getting the angles where the gunwales and stringers land on the bow and stern pieces correct. I got better at estimating the angles as I went, but some of them were far from perfect, and there were 12 of them to do. That’s where that epoxy came in handy to fill the cracks and gaps. In fact, those are the only points where I used the epoxy on the build. I did not lash those bow/stern joints, just screws and epoxy. For those complex angles I tried my Japanese fine toothed pull saw, and when my arm got tired, used my saber saw. I have been casting my eye on oscillating saws I have seen for cheap at Walmart and Harbor Freight for this job on the next boat.
The second most difficult job was fitting the sharply-curved carlins surrounding the cockpit in place, and then pulled down to their landing on frame #5. It was necessary, as Dave recommends, to slit the 3/4″ square carlins lengthwise from the front back to where they cross frame #3, in order to make that turn. Then the turn down to frame #5 is perpendicular to the first turn. The dry pine made the turns, but that would have been a good place to have soaked or steamed the wood first, and maybe the slit would not have been required. All things considered, the stresses which remain throughout the framework would have been greatly reduced by soaking/steaming all the longitudinal pieces before making the bends around the frames. Maybe I’ll do that for the next boat. I will just have to make a gizmo long enough to handle 14′ stringers!
Then the frame was removed from the strongback, and the keel was lashed to the frames, again filing a relief so the lashing wouldn’t produce a bump in the fabric.
The frame was then stained. Here I made a move I later regretted. The can of stain was old, and after I removed the usual big ball of skin and glop, the stain was thick. It was late, and I was trying to get the stain on so I could do other things the next morning. I applied it anyway, neglecting to wipe off the excess completely, so it turned out much darker than I desired, obscuring the lashings in the darkness. I wanted the lashings to be more visible in the cockpit. Next time, I will use Tung or Watco oil instead. A later light sanding made it look some better. In this pic, you can see the ends of the carlins pulled down and screwed into frame #5.
I think it was about this point that I weighed the frame, and it was 26# already, which was what the whole rig was to weigh when completed. This probably resulted from using heavier woods than specified (meranti/pine vs. okoume/western red cedar). And I had yet to do flotation, coaming and floorboards, not to mention the covering and paint. Aaargh!
At that point, I roughed in the coamings from 1/4″ fir plywood I had around. Getting the coamings to conform to those sharp bends in the carlins was fairly difficult, while getting the length of the coamings to fit properly in the cockpit opening, but some cut and try did the trick. Also, from the same sheet of 1/4″ fir ply, I cut out the five 2″ wide floorboards. The coaming halves and floorboards were stained a light color, sanded lightly and coated with a water-based clear exterior varnish I had on hand. The floorboards were screwed and lashed in place with paracord per instructions. I was surprised at how nice those fir plywood parts looked when finished.
Now we have built the bones, so that is enough for this episode. Tune in for our next thrilling episode, when we put meat on dem bones.