For canoebuilding you usually need wooden strips in lengths of more than 4 meters. Boards this long are hard to find, especially in knot-free quality. If you don't have a lumberyard nearby that sells red cedar in sufficient length (which is usually available knot-free), tapering might be an option for you. This way, you can also use native wood species such as spruce or pine, which are otherwise rather unsuitable for the production of long strips due to their knottiness.
Important: Follow the usual safety rules when working with a table saw or with epoxy resin!
What is tapering?
Tapering is a method of glueing two short strips together to get a long strip. The acute glueing angle increases the surface of the bond and creates a solid strip. A rule of thumb is that the length of the taper should be at least 8 times the thickness of the strip.
Calculation example: A stringer strip of 22mm: 22mm x 8 = 176mm length of joint.
However, we recommend about 10 times the strip thickness, as the gluing surfaces are then slightly larger and more stable, while strips with this angle can still be processed well.
Building a jig and sawing the taper
To make a precise taper that will produce a straight strip, you should build yourself a sled for the table saw. It doesn't have to look pretty, it just has to work and, of course, be safe. It is necessary that the sled moves parallel to the saw blade, for which the grooves in the table of the saw can be used. A board at the rear of the sled holds the base plate together as the saw blade makes a cut through it. A block of wood serves as a fence, which is screwed onto the base plate at the desired angle of the tapering. It determines the angle and thus the length of the tapering. Very important: Align this block with a 90° angle absolutely perpendicular to the base plate. Use screw clamps to hold the stock against the fence during the cut. Be careful that the clamps are placed outside the cutting line and cannot collide with the sawblade!
Gluing the taper
For gluing the taper we recommend epoxy resin, because you have more time to clamp the strips and not as much contact pressure is needed as with wood glue. Tape the table with packing tape beforehand so that the strip can be removed from the table later. Place the first strip on the table and fix it with clamps so that the angle of the later joint is facing upwards. Now position the second strip on top of the first one so that the angles of the joint match. Move both strips to a position where they lie flat against the table and the transition on the top of the strips can hardly be felt. The position of the second strip is now marked with a small pencil mark that goes across the strip and table. The second strip can then be removed again to perform the gluing of the joint.
The epoxy resin should be warmed before mixing the two components (approx. 25-30°C) so that it is as thin as possible and can soak deeply into the wood. After carefully mixing the two components, both contact surfaces of the taper are soaked with resin and then positioned on top of each other. The second strip is placed in position with the pencil mark on the table. To make the stock straight, both pieces should be aligned straight with an aluminum lath before clamping. Once this is done, both strips are fixed to the table with clamps on the right and left sides of the joint. This will ensure that the angled gluing surfaces do not slip on top of each other during clamping and cause the strips to shift. Then the taper itself is clamped. A board should be used to distribute the forces of the clamps and to protect the strips from damage of the clamps. To prevent the board from sticking, apply packing tape to it beforehand. If you glue the taper with epoxy resin, you should not use as much force when clamping as is required with classic wood glue.
The result before and after sanding:
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