Why not Cove and Bead?
For years, the state of the art in making strip-built boats has been cove-and-bead strips. Since most boats have rounded sectional shapes, i.e. the forms have a curved shape from the sheer line to the keel line, it is inevitable that each adjacent strip is oriented at a slightly different angle relative to its neighbor. If the edge of each strip is left square, this results in slight gaps in the seam between adjacent strips.
The cove and bead system overcomes this by creating essentially, a universal joint where the rounded edge of one strip can fit tightly against the hollow edge of another regardless of the relative angle of the two strips. This system does work well, so long as the angles between the strips are not extreme, there is not too much tension in the strip peeling them apart, and you pay close attention to fitting and clamping to hold everything in place.
With complicated shapes, tight turns and twisted strips it is common that cove and bead strips will pull apart a bit after installation. The hollow cove can hide these gaps during assembly only to have them opened up with sanding and fairing. Despite the cove and bead being a universally tightly fitting joint, the strips are really under the least stress when the adjacent strips are at the same orientation. As a result, the seam has a tendency to open.
I've been building wood strip boats for nearly 40 years now and have discovered that I can most consistently create really tight seams between strips if I bevel the edges of the strips. With a carefully crafted bevel, the strip naturally wants to rest with the flat edge tightly against the adjacent plate face. You are never surprised with a joint opening up because what you see is what you get. If the seam looks tight its because it is tight.
With practice, I learned the skill of creating the required rolling bevel, by carefully dry fitting a new strip, looking at the gap and freehand beveling the new strip with a block plane. I got quite good at, but it took time and skill, and in order to insure a tight seam on the visible outside of the boat, I often opted to slightly over bevel, leaving a tiny gap on the inside where it didn't matter as much.
Developing the Tool
For years I had been thinking of a tool to assist in crafting this bevel, something that didn't require as much skill and produced better, more consistent results. I realized that instead of trying to make a new strip match an already installed strip, that I could use the forms where the new strip will go as a guide to bevel the existing strip. The new strip needs to fit tightly against the forms, so if I created a bevel on the existing strip that was square to the forms, I could leave the mating edge of the new strip square and achieve a tight seam.
I wasn't sure how I could modify the edge of the already installed strip, I thought about various sawing tools and pondered various edge tools. It wasn't until I saw a miniature shoulder plane made by Veritas that I recognized the potential of a solution. I just needed some way of holding this small tool and reference it to the forms. I tried an idea for a hand-held wood carrying jig with a built in fence. The fence would keep the plane aligned on the edge of the installed strip, and the jig would ride along the forms.
I didn't like it. It was hard to keep the plane cutting the strip edge and if the grain angle switched directions it tore up the bevel. I put it aside for awhile, but finally came back, adjusted the curvature of the fence jig and refine the function. I then made a two sided version that allowed me to easily switch cutting direction to account for rising grain.
This version really worked. Referencing off the forms the tool creates the slight bevel needed so the square edge of the new strip fits tightly regardless of the changes in curvature down the length of the boat. Now I was making tight seams accurately, without over doing the bevel and the joints were solid inside and out.
I make these tools myself in my own shop out of high quality marine plywood. I precision cut the wood with my CNC machine, then clean up, smooth and sand, finish and assemble each one to my standards. The demand for these tools has vastly outpaced my expectations. I have had to improve my manufacturing process to efficiently keep up with the demand and the response has been amazing.
If you are seeking quick assembly and don't mind an occasional sloppy joint, cove and bead is still a great system. If you don't have the tooling to make your own cove and bead strips, or want to up your game with hand fitted seams, the Robo-Bevel has improved my builds.
The Manufacturing Process
I have refactored the process for making Robo-Bevels since publishing the below video, but this gives you an idea of what is involved. I now use top quality sapele marine plywood instead of re-sawing and prepping the solid mahogany. The plywood is more consistent and stronger and uses the material more efficiently. I can also cut 12 tools in one set-up instead of one-at-a-time as shown here. I now start with the engraving of the branding on the top side, then flip the material over and machine the tool side. The interior hole is still rounded over on a router table and all the tools are sanded smooth. I then dip the tools and knobs in finish before installing the magnets and attaching the knobs as handles.
In the video below I handle each tool over a twenty times before it is done, as I have refined the process, I am down to about 7 touches per tool after the machining which is about 4 touches per 12 tools. Each step requires setup and often a specialized jig or fixture. For example I have a finishing station that holds 80 tools where I can dip the tool in a polyurethane finish, then let the excess drip off. The drips drain back down to the dipping reservoir for recycling - See the video at the bottom of the page.
Mass production of the same item like this is very different from the painstaking one-at-a-time building of a boat. A full sheet of 9mm sapele becomes 60 tools, so I usually make batches of 120 or 180 at a time. It is an interesting change in pace and I hope users of the tool enjoy the thought and care I put into making them.