27th of January, 2021.
Stitching? I thought you said this thing was made out of plywood, not fabric?
Yup. I did. One of the techniques for constructing boats from plywood is called “stitch & glue.” Basically, holes are drilled at regular intervals around the edges of the panels, and the panels are then “stitched” together using either pieces of stiff wire (e.g. fencing wire) twisted tightly together, heavy fishing line, plastic zip-type cable ties, or some combination of the above. Once all the panels are securely and tightly stitched together, thickened epoxy is used to glue all the panels together. Once the glue has set, the stitches are removed or cut away. After some other finishing work, the end result is a hull that is stiff, strong, and yet light. Even quite large boats of 30′ or more can be made this way.
What are the pros and cons of each stitching method?
Wire is strong, but requires some effort to twist up tight with pliers, and after gluing, the wire needs to be removed, otherwise, in time it can result in rust “weeping” from the hull. Fishing line can be left in, but since it’s used like thread, “sewing” an entire “seam” together before being tied off, it’s not easy to get tight all the way along the joint, especially if the joint has some curve to it and wants to “fight back”, and it really needs two people working together to do a good job. Zip-ties have many advantages over the two more traditional methods, but they need to be strong enough to handle the sometimes considerable loads without breaking, and in principle at least, should be black, not white, so as to have maximum resistance to damage from ultra-violet (UV) light. Like fishing line, the outside portions can be cut off after the glue sets, and the parts buried inside the glue can be left there without problems.
The instructions recommend a combination of wire and fishing line. I chose to go with zip-ties throughout. With such thin plywood, I reasoned that it would be too easy to over-tighten wire stitches, which could well tear right through the thin wood. While not a disaster, this would mean more work to repair and would be a considerable nuisance to deal with. Since I would only rarely be able to call on someone for assistance, fishing line was also impractical. There was also the consideration that, being so thin, fishing line might also tear through the wood, if under too much tension. Therefore, I decided to use 4mm x 100mm zip-ties, with holes drilled in the plywood 10mm from the edges. The instructions called for holes spaced 9″ apart. To reduce the load placed on any individual tie, I settled on holes spaced 6″ apart, and on high-load areas, 4″ apart, or even less.
The first job was to place the two forward panels mirrored together, and drill holes at 6″ intervals along the mating edge. After this, the same was done to the aft pair of panels.
Next, each of the forward panels for both the bottom and the sides was butted up against its corresponding aft panel, and a “butt block” was attached to the outside of the panels to join them both together using a good number of thick but short self-tapping screws. Each of the bottom panels got a pair of butt blocks due to their larger size.
In retrospect, this would have been a good time to break out the angle grinder and get rid of all those protruding points! Never mind.. “I have a cunning plan…”
Time to start stitching! First up, the pair of aft panels. Note that at this point, the ties are not pulled tight, they’re quite loose, and only held by one or two “clicks” to keep them held together. They won’t be fully tightened until the entire hull has been stitched together.
At this point, due to the curve built into them, the forward bottom panel mating edges are spaced well away from each other, so to bring them together and encourage the panels to bend into the correct ‘V’ orientation, I stack a couple of polystyrene fruit & veg boxes under them, and keep on stitching.
The next job, according to the instructions, is to flip it over, and use a 36″ piece of wood, along with some string, to flatten the bottom out to a very specific angle. To be precise, so that from the bottom of the ‘v’ to the outer edges amidships has a depth of 6″. A handy garden stake and some hoochie cord from my camping gear fit the bill nicely.
So endeth another afternoon pretending that I know what I’m doing…
Total time spent on the build to this point: 33.5 hours.
(It should be noted that Danny Greene, the designer, estimates that the sailing version of the Chameleon would require from 110 to 140 hours to build. Most people find the reality to be closer to 300 hours. Ben Clardy of “Sailboat Story” built his in just over 270 hours, which included 20 hours “wasted” due to having to correct an error. So now you know why I’m tracking my build time.)