TSCA -- How to Recanvas a Canoe

How to RECANVAS An old CANOE

by Platt Monfort, the Geodesic Airolite boat man

Try a new, simpler method.
Covering with heat shrink Dacron fabric has these advantages:

It is simpler and easy to do
It saves weight
It is not affected by mold, mildew or dry rot
Finishes smooth due to the fine weave texture

Prepare the hull

Carefully remove the rub rails, keel and brass trim cutwaters. (You will reuse these or need them to make patterns). Strip off the old canvas, gently so as to not pry off any hull planking. Repair or replace any damaged wood. West System epoxy or "Git-Rot" can be used to toughen any punky or split areas. At this point it is worth your while to strip off the interior varnish and redo it. Tighten any loose nails that might be protruding; smooth all irregularities and apply a coat of varnish on the outside.

Tools required:

Household iron and scissors, preferably pinking shears.
Best get a cheap second hand iron at Dots Good Deals.

Measure the hull girth amidships to be sure that one piece of fabric 72" wide will be enough material to do it in one piece; otherwise it will need to be joined at the center line. Now measure along the gunwale and add a foot for overlaps and that is what you need to purchase.

The Dacron has a fine texture that will not hide bumps so examine all of the hull for imperfections and make them fair. Because the fabric is heat shrunk, it will bridge over hollows. That is OK for small dimples; however large depressions should be filled with wood dough or a mix of fine sawdust and epoxy.

This fabric is applied with adhesive transfer tape along the gunwales and stems, which eliminates tacks. Actually it is hot melt glue in tape form, and that is where we start.

Prepare the iron by setting it on a scrap corner of the Dacron and slowly raise the thermostat till the fabric starts shrinking. That is about 225-250 Deg. (note this setting) This is one of the features that is forgiving. The Dacron starts to melt at about 350 Deg. and gives off a warning with wafts of steam coming off the surface first. That is 100 degrees safety margin.

This glue has a keeper paper on one side, and all that you have to do is hold the tape in place and press the tip of a hot iron on it in spots and it will melt and stick to the wood. Now remove the keeper and it is ready for the Dacron. With the boat upside down on saw horses or whatever, you need to apply the HeatnBond tape along the bottom edge of the gunwale plank, transom, keelson and at the stem. This means both sides and front face (under where the brass cutwater goes)

Now drape the Dacron on the inverted hull; then even it up in the center. Next twist it so that it is diagonal on the hull as much as possible without any edges coming up short at the stem. You should maintain a 3-4" overlap from all edges.The next trick is important and it helps to have a helper. Pull on the fabric from stem to stem on the diagonal of the cloth.You will observe a stretch on the bias that starts to fit the compound curvature. Clamp it in place on the stems. Pull it down on on each side in the center and clamp it to the Gunwales.

With the iron still set at the shrinking temp, start ironing the Dacron onto the HeatnBond tape along the Gunwales. Work in the center and go back and forth from side to side. Press firmly with the iron, and hold it in one spot for about 3 seconds until it shows a translucency and feels waxy. Now be sure that it does some shrinking at the same time. Here it may take some heat adjustment because it is important to shrink as you go. It must lay flat with no overlaps, so shrink plenty as you go. Always pull the excess fabric edge down; never towards the ends as you iron. It is right here that you can see why you must heat with an iron, not a heat gun! Don’t worry about any wrinkles or puckers along side of the gunwale; you will get them later. Just keep pulling down as much as possible.

Stop gluing when you get to about 6" from the ends. Remember that I told you that these materials are very forgiving. The tape glue has very good shear strength and that is how it is loaded on the boat; however it has low peel strength. Now is the time to check your work. If something doesn’t look right you can peel it off in any area and redo it. It may need some more tape.

At this point you can trim off the excess material on each side of the stem, leave 4-6" extra for overlap. Slit the material on the center line to about 1" short of the point where the curvature starts. Work on one side and front face of the stem.

Starting at the end of the slit, trim off the excess so that you have a 1" overlap on the far side. You should be able to shrink the fabric to lay flat otherwise cut it into tabs. As you approach he gunwale, glue that last 6" to close the gap with glue all around.

Add some more heat tape at the stem to cover the Dacron where the second side will land, just the far side and the stem front face. Now complete the second side the same as the first and trim off the Dacron to the edge of the front face.

SHRINK THE SKIN

This is the moment you have been waiting for! Shrink all over the hull surface. Do not heat-stick it to the keel until it is tight all over. It is very important to remember to keep the iron away from the areas of the heat tape (gunwale and stem), because if you re-heat there while the shrinking tension has been applied, it will pull loose. Because the gunwale is on the bottom edge it is easy to slip and go too low. So I suggest that you clamp a piece of wood (like the rub rail) in place as a guard while you work close to the gunwale.

One thing to watch out for is to not run the iron on top of a wrinkle and press a fold... they are hard to remove. Some patience with the tip of the iron will get rid of the fold. You will find that if you sweep the iron lightly over the flat areas, wrinkles will pull out of other places. Don’t over do shrinking; just do it enough to get it smooth. Work in a well lit area and look at reflections on the skin from different angles to spot irregularities. Now set the heat tape slong the keelson.

STEM DOUBLER

This is is an overlay piece of fabric to reinforce the Stem... not necessary, but a nice touch. Cut a piece of scrap fabric, on a 45 deg. bias, about 4" wide and about 1" longer than the overlap area at the stem. Make a half circle round on one end. For appearance sake it is quite important that it have pinked edges. Stick a strip of adhesive tape down the stem, starting with a 1" overlap on the slit cut.

Now adhere the doubler in one small 3/8" dot at the beginning of the tape. Next you pull on the other end and observe how it stretches on the bias to fit flat against a compound curve. Keep it centered as you pull it down and iron it to the stem front face.

Mark the edges with masking tape. Then one side at a time, carefully lift the fabric back so that you can apply some heat tape. Cut patterns from sheet stock. Lay the cloth back in place and set the adhesive with the iron at a no shrink setting.

SEALING THE DACRON

The simplest treatment is a couple of coats of Moore's exterior acrylic latex paint with Penetrol additive. Let it dry thoroughly at least a week. The surface can be toughened with an overlay coat of original-formula oil-based ZIP GUARD varnish.

One word of caution about the oil-based finishes, they have a tendency to loosen and lift the HeatnBond adhesive. Don’t lather it all over the adhesive areas. A light coat especially over the latex will probably be OK.

When you replace the exterior parts, set them in bedding compound or epoxy to avoid leaks into the woodwork.

3.7 oz 70"/ 72" width DACRON FABRIC, $8.00/ yd + P&H, is available from:

MONFORT ASSOCIATES
50 Haskell Road
Westport, Maine 04578

pmonfort@ime.net