The Best Canvas Filler for Wood-Canvas Canoes

by Mike Elliott, Kettle River Canoes

These days, the world of wood-canvas canoes is very small indeed.  It seems strange to think that there may be trade secrets in such an exclusive community.  However, just try asking a wood-canvas canoe builder for his or her recipe for canvas filler and be prepared to offer the secret handshake before another word is spoken.  Fortunately, the Wooden Canoe Heritage Association has been publishing filler recipes for at least a couple of decades now.  Without their help, I would not have been able to restore my first canoe some 18 years ago.

Now, I would like to declare my favourite canvas filler.  To my mind, it is the best filler for wood-canvas canoes.  It was introduced to me about eighteen months ago by Dave Lanthier of Kamloops, British Columbia.  He has been using a latex-based lagging compound to fill the canvas for several years.  Dave Bobbi of Shuswap Canoe Works in Tappen, BC (now deceased) taught him the technique.  Now, I have been using it for over a year and I am a convert.  Long live latex-based filler on wood-canvas canoes!

Dave recommended using either CHIL-SEAL® CP-50A MV1 or BAKOR® 120-09 lagging compounds.  These are commercial products used to seal air-duct systems in commercial buildings.  These compounds are specifically designed to fill canvas and make it water-proof.  They have the added bonus of being fire resistant as well.

I purchase a 5-gallon (20 liter) pail of BAKOR® 120-09 for less than $240CND.  Since the pail does about eight canoes, it works out to less than $30/canoe or roughly the same as the traditional oil/silica-based fillers.  One of the major advantages to latex-based lagging compound is that it is water-based.  There are no nasty volatile organic compounds (VOC’s) to contend with.  Clean-up is accomplished with nothing more than a bucket of water.  Most importantly (for anyone trying to restore a couple of dozen canoes in a year), where traditional oil-based fillers take about 30 days to dry before paint can be applied, the drying time for latex-based filler is about 30 hours.

I use a 6” (15 cm) foam roller to apply the lagging compound directly from the pail.  Apply the compound to about a 6’ (2 meter) section of canvas on one side of the canoe.

Once the compound is applied evenly to the canvas, I use a 6” (15 cm) putty knife to remove excess compound and smooth the surface.  Dave uses a wallpaper smoother for this.  I suppose you can use whatever you have on hand.  Apply the compound and smooth it as quickly as good technique allows.  You want to be able to smooth the compound before it sets up — we are talking about a matter of minutes, so there is no time to fuss and fret.  Get it on, remove the excess along with any obvious ridges of filler on the canvas and move onto the next section.  It is important to maintain a wet edge as you apply the compound from one section to the next, so keep moving.  By the time you have worked your way around the entire canoe, it is time for the next coat.

I find that the compound works very much like sheet-rock mudding.  The first coat is a base coat, the second coat is a fill coat and the third coat is a smooth or finish coat.  A fourth coat can be applied if necessary, but I was very pleased with the results after three.  It takes the better part of a full day to complete the filling process.  Then, just walk away and let the filler dry for a couple of days.  Many people respond to my account of this process with: “There must be a catch.  It can’t be that easy.”  Well, if there is a catch, I haven’t found it.  It really is that easy.

Once dry, the compound is sanded smooth with 120-grit sandpaper.  I find it behaves very much like the traditional oil-based fillers from here on out.  I install the brass stem-bands the same day as the sanding and begin painting the canvas (with alkyd enamel thinned 12% with mineral spirits) the following day.  It sure beats having to wait a month for the oil-based filler to dry.