How to Make and Install Half-Ribs in Wood-Canvas Canoes
March 5, 2017
by Mike Elliott, Kettle River Canoes
About 130 years ago, fishing guides on the east coast of North America (most notably in Maine, New Brunswick and Quebec) started building wood-canvas canoes that they could use in order to take their clients up and down the shallow, rapid salmon rivers in the region. They used the local birch bark canoes as templates. The guides would be standing up all day in the canoe as they poled it upstream and down or held the canoe in place while the client fished for salmon. The canoes needed to be stable and rugged with a strong, comfortable bottom. They designed canoes that had wide, flat bottoms which made them stable with a very shallow draft. To strengthen the hull against the inevitable encounters with rocks, they did one of two things:
a) Build the canoe with lots of ribs spaced very close together (0.5″ to 0.75″ – 13 mm to 19 mm apart).
b) Space the ribs normally (1.5″ to 2.0″ – 38 mm to 50 mm apart) and insert extra ribs between them that extended across the bottom of the canoe. These “half-ribs” created a strong, comfortable floor in the canoe.
At my canoe restoration shop, a client sometimes asks me to insert half ribs into their canoe in order to create a stronger bottom. Unfortunately, if you simply pressed shorter ribs into the bottom of the canoe between the regular ribs, the hull would become misshapen – especially if the bottom was not entirely flat. Therefore, retro-fitting half-ribs into a wood canvas canoe is done in the following way. Note, that this is done while the old canvas is off – before a new canvas is stretched on.
1) Cut and shape the new rib material from clear, straight-grained cedar. The half-ribs are about 1″ (25 mm) wide and the same thickness as the original ribs in the canoe. The sides of the half-ribs are chamfered about 10°. Sand the top edges lightly to round them off a little. Soak the new half-ribs for 48 to 72 hours. Then, steam them for about 50 to 60 minutes and bend them over the outside of the hull between the regular ribs. Allow the new ribs to dry for at least 48 hours. Just as when creating an exact replica for a broken rib in the canoe, the half-ribs are bent in a location so that the shape of the rib on the outside of the hull is the same as the dimensions required on the inside. The taper of the hull is such that the inside dimensions are achieved by bending the rib one station closer to the near-end of the canoe. Precision is not as critical for half-ribs as would normally be required since the ribs will not be curving around the chine of the canoe. Use a pencil to mark the centre-line on each new rib.
2) Remove the new ribs from the outside of the canoe and place them in the required positions between the regular ribs. Make sure the centre-line on each new rib is lined up with the centre-line of the canoe. Hold the new ribs in place with spring clamps on the inwales.
3) The length of each half-rib will vary so that they match the taper of the hull dimensions. The actual length of each rib is entirely up to you. Use a straight-edge to help determine the length of each rib and use a pencil to mark both ends.
4) One at a time, cut each half-rib to length.
5) Use a random-orbital sander and 80-grit paper to chamfer the ends of the rib.
6) Place the half-rib back into the desired location and secure it with one tack about halfway between the centre-line and one end of the rib. Make sure the rib is centered between two original ribs. Repeat this procedure on the other side of the rib making sure that the half-rib is centered between the original ribs. This can be done by one person, but is much easier when one person holds the half-rib and clinching iron while a second person drives the tacks with a cobbler’s hammer.
7) Once the half-rib is centered and straight, secure it with a full complement of tacks.
8) Repeat steps 4 to 7 for each half-rib in turn.
The entire canoe restoration process is described in my book – This Old Canoe: How To Restore Your Wood Canvas Canoe.
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