Tuesday, September 29, 2015

Building a Cedar Strip Sailing Canoe

Before I built the skin on frame canoe my dad was mentioning that he "needed" a sailing canoe to teach the grandchildren (my neice and nephews) to sail.  He was looking for a plywood hard hine design similar to Michael Storer's "Beth" sailing canoe.  Plywood has its place in boat building, even in building hulls, but I feel the simplicity of building with plywood does not make up for the fact that it is difficult to prevent a plywood boat from being ugly.  I was pushing for something more like Paul Fisher's Carrick sailing canoe, but it was a bit too dramatic for dad's taste.  In the end I managed to convince dad to try the cedar strip method, and I modified the plans for Skip Johnson's EasyB 14 foot version to meet the 34"+ beam (width) requirement dad had set for the canoe.  Modification was easy since the canoe was designed with progressive parabolic curves meeting at a zero curve point along the bottom, so I just added a correcting width measurement to the flat of each mold shape the using the same rate of change.


Layout of the building jig was simple.  We used some spare scraps to build a long flat backbone/table and then spaced the molds properly and kept them parallel and vertical with a temporary stinger down the bottom.


Dad selected some good Western Red Cedar and Top grade Radiata Pine 1x6 boards, and I spent a few hours machining the strips.  The boards were all relatively short, I think 8 feet.  We had decided that since every strip would be sandwiched, butt joints should be easy and hardly affect final strength if they were all spaced out.  That made finding quality wood a lot easier since it doesn't have to be the full length of the boat, but it does mean machining even more strips.

We sized the strips 3/4" x 1/4" with a bead on one edge and a cove on the other so that they will fit together nicely with lots of glue surface when assembled.  For machining, that meant running every strip through the table saw once and then the router table twice.  By the time I was done I had tender spots on my fingertips from pushing wood and numb spots in my hands from holding it down against vibration.

I didn't know how awesome the power planer was at this point, otherwise I would have also sent every strip through the planer twice so all the strips would match dimensions perfectly with no saw marks.  What's another couple hours of machining?


The beads and coves on the strip edges that make strip building so much easier.


The sheer is set with a few wooden scraps screwed to the molds at the sheerline, and we laid two double-height strips of pine to begin the build.  After the pine, we placed one cedar strip for a sheer stripe and then continued in pine until we switched back to cedar at the turn of the bilge near the waterline.


 

I wanted to try a method of strip building that wouldn't require staples or nails to hold anything down nor together.  The method requires some fiddly non-traditional materials and approaches.  Each strip is held against the last by #64 rubber bands. Peg board was chosen for the molds so that we would have a myriad of locations to secure the rubber bands that hold down each strip without having to drill them all ourselves.  A few 1/4" dowel rods were cut into a million little pegs for the rubber band anchors, and also set into the cove on each strip to protect the wafer edges from the rubber bands.  The cove is set upwards for ease of gluing, and waterproof Titebond 3 was the glue of choice.  With a dry-to-work time of about 20 minutes, that allowed dad and I to place a strip on one side while the other side dried and move back and forth without stoppping... it still took three days to strip the hull.    As the hull sides got taller, it became necessary to use blocks on the side of the hull under the rubber band helped keep the earlier strips against the molds.










Packing tape held the ends together as we neared the end.
We had decided to just fiberglass the ends closed, but in the future I would stagger each strip over the last left to right like interlacing fingers as the strips are being laid.  It would both improve appearance and it would be glued securely during the build and before coming off the molds.



Once we rounded the bilge and had made it to the nearly-flat bottom, dad opted to finish it with some ultra light 4mm Okume plywood.  At first I was opposed to any use of plywood, but then I realized the bottom would (and should) be painted inside and out, and I'm pretty sure the plywood will be more durable than the cedar strips in the bottom during groundings and just from the constant tension of weight in the boat and wind in the sailing rig.
So, out came the zip ties to hold it together while we laid fiberglass tape and epoxy.


Then the hull shell was finally lifted off the molds...  carefully because it was very floppy and fragile at this point.   It was only about 15 pounds!



I want that to be the rig for this boat.  It is a 78 square foot triangle on a 16 foot tall mast that dad used on his now-defunct sharpie sailboat.  The canoe will actually be using the 50 square foot sprit rig from my now-defunct dinghy, but I will probably shape the mast on the dinghy rig to be interchangeable with this monster for those days where you just want to hang off the rail and get wet, risk of capsize be damned.


Dad had already decided he wanted a lot of bouyancy and rigidity.  He was also pretty excited at this point to see the lovely shell come together. So, the next time I came back to help on the build, he had already drawn up some frames for full decks with hollows underneath, and cut and epoxied them into place.  In light-weight fashion, he used the 4mm Okume plywood and even added holes wherever he was able.  I decided my weight obsession is either genetic or contagious.


Then we laid 4oz fiberglass cloth normally used on surfboards and saturated it in epoxy.




Dad added the remaining deck/bouyancy compartment frames and we installed the compartment sides.  Dad cut even more lightening holes in the main frames, and used the lightest white fir scrap wood he had for deck stiffeners fore and aft.  Then he drilled a bunch of holes in them as well.



Instead of adding heavy hardware and screws for a bow eye, why not just drill a hole and chamfer the edges?  My thoughts exactly.


Then we nailed down the decks with lovely copper ring nails (and epoxy), and prepared the bottom for fiberglass.  When I came over to lay fiberglass and epoxy on the bottom, dad had already machined some tiny mahogany strips to finish the ends and secured them with lovely copper ring nails.  Again, we used 4 oz cloth on the bottom, which is so thin it was easy to wrap and lay nicely around the ends.

 

Decked and glassed





And this is the rig that will end up in the boat.   It is repurposed from our old dinghy.  At 50 squre feet it will still make this boat fly.  I expect dad will wrap up the build this winter after he finishes the shelves in his shop.  



1 comment:

  1. I built a Guillemot kayak about 15 years ago from Nick's book: Strip Built Kayak. It was a lot of fun, but I never thought of using peg board for the frames. Mine were plywood and I used staples. It was my first wood / epoxy project and it ended heavier than design because I used to much epoxy. I still enjoy paddling it, though.

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