Building a Cedar Strip Kayak: The Details: Stripping the Hull
This is the step in the build process where your kayak actually starts to look like something. This can be a source of motivation. From now until you finish, you will probably find you’re going to the work shop and looking at the kayak from many different angles then placing your hands on the wood to feel the shape and search for flat spots or other inconsistencies.
For this project I started with left over strips from my last boat build, which was a 16 foot canoe. Needless to say, but I’ll say it anyway, these were not the best quality strips. Some were good, but some were also culls and leftovers. But I made them work because I wanted to save some money on this project, knowing I would have to do more patching, shaping and sanding. In the future, if there is another boat build in the future, I would add an extra step to the fabrication of the strips. I would invest in thickness planer and cut the strips a little thicker. Then I would plane them to the desired thickness so that they would all be of a consistent thickness. This would make the stripping process go much more smoothly as well as make the sanding, shaping and patching steps go much more quickly. I’m sure the boat, upon close inspection, would also be somewhat better looking.
The strips I used were of various lengths, but none were the total length of the 17 ft. kayak. I joined the strips with a simple butt joint, taking some care to ensure the joints of adjacent strips did not line up, by placing the strips starting from the opposite end of the previous strip. I learned to use the shorter strips and butt joints in my last boat build. I tried scarf joining the strips but that took too long and the joint was still noticeable. I tried to take some care in matching wood color of the strips on either side of the joint.
The strips were stapled to the forms using 9/16” staples, beginning at the sheer clamp, with bead side down, cove side up. The cove side of the strip makes a convenient trough to hold the bead of glue. The strips are attached so they run past the stems, and will be cut flush with the stems later on. When I came to a butt joint I usually tried to staple the two strips together, but the next strip applied helped to hold them in place. I attached 3 strips at a time on each side, working up towards the bottom of the hull, to allow the glue to set overnight before attaching the next 3 strips. The bead of each strip was firmly pressed into the cove, holding the glue, of the strip below it before stapling. Once the three rows of strips were attached, I cleaned them with a rag to wipe off excess glue. Then I went back pressed the strips together and where I found that they moved slightly causing more glue to be pressed out of the joint I held them together with a long piece of masking tape pulled down across the strips.
Once you get to the section where the strips are attached to the rounded part of the hull (bilge) it becomes more difficult. The planks want to twist and the bead and cove joints do not fit together as well. You may have to use some creative clamping methods to help hold them in place, like a bungii or string wrapped around the hull and wedges of wood placed underneath to apply pressure to the strip.
Once you start to attach strips to the bottom of the boat hull, you will want to attach them to only one side until you cross the center line of the boats bottom. Then a long line is marked on the bottom strips. I stretched a string from a nail in each stem at its center line. The string should be high enough not to touch the wood or it may get stuck and skew the line. I traced the shadow of the string, since my lights are directly overhead the line was directly beneath the string. Then, using a sharp exacto knife I cut the strips along the line. After trimming away some (but not all) of the strips extending past the stems on each end, you can start attaching strips to the other side of the kayak again. The ends of each strip will have to be cut on an angle to butt against the straight edge you just cut. The last strip on the centerline may just be a long sliver. I placed a couple pieces of masking tape over the small opening for the last plank and cut the tape to its shape. Then the tape was placed on piece of planking, which was then cut to that shape. You made need to patch some to the joints that were not so perfect with small slivers of wood glued into place.
A word about staples and glue: The strips can be attached without staples by using clamps if you wish the line of staple holes at each form not to be visible in the finished kayak. That is what I plan for the deck. Using staples is much faster and I actually don’t mind seeing the tiny holes. I think it adds some character. On this project I used Titebond III wood glue. It comes in two colors, white and tan. I wanted to use the tan color but couldn’t find it at the local big box store. I tested the glue and, as advertised, it did dry to more or less a transparent or translucent color, which was not too bad. That is much better than the yellow of the original Titebond or Titebond II. Also, this glue can be applied at lower temperature (47F) which was a big consideration for me.
Once all the strips are attached, they need to be trimmed flush with the lower 2/3 of the stems. The outer stems should be checked to make sure the ends will not extend past the ends of the inner stems at the boat bottom. They should be trimmed to provide at least 1 inch of distance then gradually tapered slightly towards that end. The outer stems are then mortised into the strip wood which is on top of the inner stem. The strips that are not part of the mortise should be trimmed with a wood rasp or sure form plane to ensure they are flat with the surface of the inner stems. I set the outer stems in place and using the plane to trim away parts of the inner stem and strips, made sure of a fairly consistent fit.
The outer stems are attached with epoxy, thickened with wood sanding dust. The edges of the strips and inner stems are first coated with un-thickened epoxy to seal the wood. The outer stems are attached with wax coated wood screws through clearance holes to pilot holes drilled in the inner stem. The screws should be tightened firmly but not so tight as to squeeze all the glue out of the joint if it happens to be a perfect fit. Mine was not.
After the stems glue joints cured , I removed the screws and plugge the holes with glue and hand whittled dowels. I removed all the staples and shaped some of the rougher, and more uneven spots of the stripped hull with a bladed plane and sure form plane. Care should be used so as not to dig the planed too deeply into the soft cedar. Light pressure on the tool will help. Next I rough shaped the outer stems. Using more wood sanding dust thickened epoxy, I then patched the larger gaps between strips, all the butt joints, any gaps near the stems and any where I could find that needed extra fill.
Once that round of patching had cured I sanded the hull with 40 grit sand paper attached to stiff sanding blocks. After cleaning off the dust I mixed up another batch of epoxy and sanding dust to patch any remaining voids. The next steps were:
- 1 course of sanding with 40 grit on stiff sanding blocks
- 1 course of 60 grit sanding with ROS
- 1 course of 80 grit sanding with ROS
- 1 course of hand sanding with 100 grit where needed
- 1 course of 120 grit sanding with ROS
- Wet the hull with water to raise the grain
- Final course of 120 grit sanding with ROS
Ready for Fiberglass!!
- Building a Cedar Strip Kayak: The Details: Lofting the Plans
I decided to build another cedar strip kayak. I’ve kind of had an itch to build another boat. I previously built two cedar strip canoes and one cedar strip kayak. I want to take the less expensive route, so I will do some things to cut costs.
- Building a Cedar Strip Kayak: The Details: Making and Setting Up the Forms
Making forms that determine the shape of the hull and deck, then setting them up on a build table for construction of a Cedar Strip Kayak.
- Building a Cedar Strip Kayak: The Details: Stems and Sheer Clamp
The stems on a wood strip kayak are ¼ strips of wood which are steamed, shaped and glued together with thickened epoxy. The sheer clamp is what is used to attach the deck to the bottom of the hull.
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