Building a Cedar Strip Canoe, the Details: Making the Forms
This is the second part of the more detailed description of how I built my third cedar-strip canoe, a shortened Freedom 17 design. It expands on my article "Building a Cedar Strip Canoe: The Basics."
Cutting Poster Boards
Now the plans are lofted, or you have purchased plans, and you have hull outlines on a large sheet of paper. Since the cross section of the hull is symmetrical, only half of the hull shape is needed for each form.
I cut three small windows in the plans, each about ¼” X 1/2: at the top of the vertical center line, at the end of the horizontal baseline, and at the intersection of those lines. Then I aligned the plan lines with the edge of a poster board and traced the hull outline onto the poster board using carbon paper. Take care not to allow the alignment to slip. You could use tacks or tape to hold the plan sheet to the poster board.
This results in a tracing of a half-hull cross section. I repeated this for each outline, then, using scissors, I cut the half-hull poster boards. I was hoping the poster board edges would be square.
Cutting Out the Forms
Next I purchased a 4’X8’ sheet of 5/8” particle board. I had a sheet of OSB of similar thickness laying around, so I used that also. Using a carpenter's square, I drew a straight vertical line on the sheet of particle board, far enough away from its edge for the half-hull cardboard cut-out I was about to trace. I drew a line perpendicular to the vertical line 4 inches from the edge of the plywood. The side and bottom edges of the cut-out were lined up along the horizontal and vertical lines I drew.
Then I traced the outline, flipped it, and traced the opposite side. I repeated this step until all the cut-outs were traced onto the plywood. I marked each side of the hull outline where the sheer was located. I also drew a rectangular area below each outline between the edge of the plywood and the 4-inch line. This would be the pedestal for the form, which is the area where the form is mounted to the station block. The I drew a line from an inch below each sheer point to this rectangle.
I used a jig saw to cut out the forms. I had a newer saw but the blade tended to wander around the curves so I switched to my old saw with a broken base plate. That worked much better but was slower. After each form was cut out, I smoothed the edges a bit with a sure form plane.
Mounting the Forms
Next I drew the length of the strong back table (mine already had one from before) and mounted the station blocks (1-1/2 x 1-1/2 inch 12 inch long blocks). This design was for a 17-foot canoe but I wanted mine to be about 16 ft or maybe slightly less. The design called for the forms (or stations) to be spaced every 12 inches. I spaced mine every 11 inches.
First I drew a line in the center of the table perpendicular to the long center line then repeated it from there every 11 inches towards the bow and stern. The forms should be centered over each line, so the station blocks need to be mounted one-half of the form thickness from each of those lines. The station blocks should be on the bow or stern side of the forms depending on which side of center.
I drilled clearance holes in the forms and mounted them to the station blocks, being careful to align the vertical pencil line on the form with the one on the strong back table center. A string stretched from end to end can help with alignment. The forms were attached with drywall screws.
The stem forms are mounted at each end along the center line of the strong back and butted up against the second to last form on each end. The top of each stem form should be about ¾” below the top of the form it touches to allow for attachment of the inner stem, which is a laminate of three ¼” strips. I attached some guide boards along the base of the stem forms. I cut 2-inch diameter holes in each stem form to allow the laminations to be bent around the forms and clamped once they are steamed. A long thin strip should be nailed to the top of each form to tie them together. This will be removed later but helps with stability during the stripping process.
The previous step
- Building a Cedar Strip Canoe: The Basics
A practical account of my experiences and a brief guide to building a cedar strip canoe. It includes links to stories of using the canoe for wilderness camping and fishing.
- Building a Cedar Strip Canoe: The Details: Lofting the Plans
A description of how to create canoe plans from a table of offsets which are hull measurements. Lofting. Expansion of "Building a Cedar Strip Canoe: The Basics". More details this time.
The next steps
- Building a Cedar Strip Canoe: The Details: Making the Stems
A description of how make the stems. Expansion of "Building a Cedar Strip Canoe: The Basics". More details this time.
- Building a Cedar Strip Canoe: The Details: Cutting and Milling the Strips
A description of how cut and mill the strips. Expansion of "Building a Cedar Strip Canoe: The Basics". More details this time.
- Building a Cedar Strip Canoe: The Details: Stripping the Hull
A description of how to attach the strips. Expansion of "Building a Cedar Strip Canoe: The Basics". More details this time.
- Building a Cedar Strip Canoe: The Details: Seats, Gunnels, Decks and Yoke
A description of how make the seats, yoke, gunnels and decks. Expansion of "Building a Cedar Strip Canoe: The Basics". More details this time.
- Building a Cedar Strip Canoe: The Details: Sanding and Fiberglassing
A description of how shape and sand the hull then apply fiberglass and epoxy. Expansion of "Building a Cedar Strip Canoe: The Basics". More details this time.
- Building a Cedar Strip Canoe: The Details: Final Steps
The final steps and results of my second cedar strip canoe build.
- Canoe Flotation Chambers
One of the things I fear is having my canoe sink or scuttle if I ever capsize. So, as an extra measure of caution I decided to add floatation chambers to the bow and stern.