Stretching Canvas on a Wood-Canvas Canoe

by Mike Elliott, Kettle River Canoes

At first glance, stretching the canvas onto the canoe appears to be very tricky – and you would be right.  It is a complex process that requires a lot of time and effort just to get set up.  Once completed, you have a skill that you will probably never use again.

Start by checking the hull one last time.  Re-clinch tacks that are raised above the hull as you run your hands over the outside of the canoe.  Any new planking still raised above the rest of the hull is sanded smooth.  Brush the hull and make sure there is no debris left behind to get trapped between the hull and the canvas.

Now, let’s talk about canvas.  I normally use #10 untreated artist canvas weighing 14.5 ounces per square yard.  Canvas 72” wide will work for most canoes.  Large canoes, such as freighters, often require canvas that is 96” wide.  Since I purchase canvas in 100-yard rolls, I have the advantage of being able to set up the roll on a rack.  This allows me to pull the required length directly over the upside-down canoe.  There must be enough canvas to extend about 18” (45 cm) past each end of the canoe.  This means a minimum of 19’ (5.8 meters) of canvas for a 16’ (4.9 meters) canoe.

Secure the canvas to the inwales with spring clamps before turning the canoe right-side-up.  With the canoe sitting in its canvas envelope, make sure the ends of the canvas are even before attaching the canvas clamps and securing them to the wall and the come-along.

With everything in place, remove the cradles and make sure the canoe is sitting squarely in the centre of the canvas envelope.

If you started stretching the canvas now, the canoe would pop right out of the envelope.  To keep it in place, use two-2×4’s as vertical struts wedged between the ceiling and the canoe.  My shop is an old warehouse with thick fir planks in the ceiling.  Other locations would require re-enforcements in the ceiling.  Protect the bottom of the canoe with 2’ (60 cm) lengths of 2×6.  The bottom end of each vertical strut is set up slightly further away from the come-along than the top end.  As tension is applied, the bottom end of each strut is pulled closer to the come-along bringing them closer to plumb.  Another option is to weight down the canoe.  I’ve used a number of 5-gallon pails filled with sand to push the canoe into the envelope as the canvas is stretched lengthwise.

With the canoe pressed firmly into the canvas envelope, crank the come-along a number of times to take up the slack.  Then, make sure that all of the clamps and struts are secure.  The last thing you want is for something to let go under all that tension.  Use a utility knife to cut straight down from the top edge of the canvas in line with the end of the canoe.  Stop about 4” (10 cm) from the sheer-line of the canoe.

Use a large “clothes-pin” to hold the sides of the envelope close together at each end of the canoe.  These clothes-pins can be no more than two lengths of hardwood (2’ x 1” x ½” – 60 cm x 25 mm x 13 mm) clamped together at the top with a C-clamp.  If you want to get serious about it, you can make proper one-piece units reinforced at the top with a ¼” bolt, washers and a wing-nut.

A pair of canvas pliers will be used to stretch the canvas along the sides of the canoe at the sheer-line.  They work best when there is about 3” (8 cm) of canvas extending above the top of the inwales all the way around the canoe.  So, put a new blade in your utility knife and trim the canvas.

In my first attempts, I trimmed the canvas down to about 6” above the sheer line and then carefully trimmed away more canvas as I worked around the canoe with the canvas stretchers.  With over 100 canoes under my belt, I trim it to the desired height by eye in one quick step.  However, don’t cut too close to the top of the inwales.  There must be enough canvas to grab with the pliers, so take your time.  

Once the canvas is trimmed all the way around the canoe, the come-along is cranked until the canvas is stretched tightly around the canoe.  The amount of tension required varies with each canoe.  Tap the canvas at the end closest to the come-along.  When it rings like a tenor drum, start to attach the canvas along the sides.

Starting at the centre of the canoe, pull the canvas tight with canvas pliers.  To do this, rest the jaws of the pliers on the top of the inwale and grab the canvas.  Pull the pliers and hook the large “fulcrum” of the pliers over the inside corner of the inwale.  Rock the pliers to about a 45° angle and secure the canvas at the top of the planking with a 1” (25 mm) brass tack.  For a long time, I used ½” (13 mm) Monel staples and a staple gun.  In my opinion, the tacks do a better job.

Start by securing the canvas at four rib-tops on both sides of the canoe near the centre.  Sags in the canvas between the tacks indicate insufficient lengthwise tension in the canvas. If more tension is required, remove three of the four tacks on one side and crank the come-along a number of “clicks”.  Re-tack the canvas and check to see if the sags are gone.  If not, repeat the process with more “clicks” in the come-along.  There is a “feel” developed in terms of the amount of tension needed for each canoe.  If it is your first time, just keep an eye on the sags between the tacks.  When they disappear, the tension is right.

Once the canvas is sitting tight against the hull between the tacks, attach the canvas at three or four more rib-tops on both sides of the canoe.  Work from the centre towards both ends.  As with most things in a canoe restoration, your first attempts involve a lot of trial-and-error (with an emphasis on error).  It is all part of the learning process.

Once the canvas is attached to every rib-top, release the tension from the come-along and remove the struts.   Support the canoe with the cradles and cut the canvas away from the clamps being sure to leave at least 6” (15 cm) extending past each end of the canoe.

To close the ends of the canvas around each stem, turn the canoe upside-down and raise one end to a comfortable working height.  This is done by supporting it on top of the cradle with a scrap length of 2×4.  Crease the canvas at the centre-line and cut along the crease from the point where the stem turns away from the canvas at the bottom of the canoe.  This creates two flaps of canvas – one on each side.  Each flap is trimmed to leave about 3” (8 cm) of canvas extending past the stem profile.  Again, care must be taken to avoid cutting the canvas too close to the canoe.  There must be enough material to grab with the canvas pliers.

The end of the canvas is closed around the stem by stretching and tacking one flap around the stem, trimming away the excess canvas and then doing the same on the other side.  Start by stretching the canvas at the point where the stem turns up from the bottom.  Lever the pliers along the stem and pull the canvas tight along the centre-line of the canoe.  Secure the canvas to the stem with 3 or 4 tacks spaced about 1” (2.5 cm) apart.  I use short tacks to attach the ends of the canvas to the canoe stem (about 5/8” or 16mm).  Next, move to the stem-top and use the pliers to stretch the canvas flap.  Make sure the canvas along the sheer line is sag-free and secure it along the stem with 3 or 4 tacks spaced about 1” (25 mm) apart. I alternate from top to bottom working towards the middle of the stem until the entire flap is tight and securely fastened.  Now, trim any excess canvas along the open side of the canoe stem.

The second flap is stretched, tacked and trimmed the same way as the first.  As each flap is secured to the stem, check to ensure the canvas is stretched smooth with no sags, creases or puckers.  You may have to fuss a bit with the tension of the canvas along the sheer line near the end of the canoe in order to create a tight fit at the bottom of the stem.  The length of the cut along the centerline of the canvas may also have to be extended ever so slightly to remove any puckers.  All this varies with the shape of the stem profile.  Your canoe may be straight-forward or may require some fussing.  As long as you stretch the canvas well both where the stem curves away from the bottom and at the stem-top, you ought to avoid any major difficulties.

Once both ends are closed and trimmed, support the canoe on top of the both cradles and get out the propane torch.  Before the filler is applied, the canvas knap must be removed.  Knap is the fuzzy balls of cotton extending above the weave.  This fuzz is burned away with a torch.  The only trick here is to keep the torch moving.  I’m not sure if it is absolutely necessary to ensure a smooth surface because I’ve never omitted this step.  You can certainly experiment and see if the finish is rougher without singeing the knap.  Meanwhile, I’ll stick with the traditional methods.

As you work the torch over the canvas, keep an eye open for any thread-ends that may ignite as you pass close to the edges.  Make sure these are extinguished.  Otherwise, the thread will continue to burn like a wick along its full length and cut the canvas in two.  I was able to catch a burning thread before it did irreparable damage.

So, there it is.  Unless a wayward tack has become trapped between the canvas and the canoe, it is ready to be filled.  You will find the learning curve a little steep.  Just remember to breathe and smile. Are we having fun yet?