How to Make a Fiberglass Canoe

Fiberglass is a versatile material for canoe building.

Making multiple fiberglass canoes is less expensive per canoe than making one. That's because you need a canoe mold. If you can buy, rent or borrow one, the rest of the job is relatively straightforward. The details involved in building a solid fiberglass canoe can be managed by reading the instruction sheets that come with the chemicals. If you get stuck on something, jump on the American Canoe Association online forum and find someone who's built one.

Things You'll Need

• Canoe mold--male
• Soap and water
• Bucket
• PVA parting compound
• Car or surfboard wax
• Epoxy fiberglass resin
• Hardener
• Respirator
• 1 oz. E-glass fiberglass large enough to drape over the outside of the hull and cover it completely
• 4-6 oz. E-glass fiberglass fabric--plain-weave thickness: 0.0093 inch
• Scissors
• Disposable mixing bucket
• Stirring stick
• Plastic spreader or mohair roller
• Trim razor knife
• Sandpaper and sander
• Acetone
• Ash or other hardwood 2-by-2s -- enough for three or four thwarts and four seat supports the width of the canoe
• 1-by-8 hardwood plank, 4 feet long--enough for two seat bottoms
• 1/8-inch hardwood slats--3 3-foot-long pieces, 2 inches wide
• 40 feet of cove molding for gunwales
• 1 pound of 1-inch screws
• Draw knife
• Sander with coarse, medium fine and extra fine sandpaper
• 1-, 2- and 3-inch brushes
• Plastic or metal flat-edged spreading tool
• Marine sealer
• Latex or rubber gloves
• Duct tape
• Power buffer

Instructions

1. Clean dust or dirt from the canoe mold. Cover the outside with two coats of auto wax and buff to a high shine. Buff between coats. Brush or spray the entire molding surface with PVA parting compound. Let it dry.

2. Brush or spray on the fiberglass gelcoat, following manufacturer's instructions. Add pigment to the gelcoat mix in the proportions recommended for the color you choose. Do this for every batch of gelcoat mix. Apply one coat. Let cure overnight. Apply a second coat to ensure even thickness.

3. Cut 1-ounce fiberglass mat in a single sheet to cover the hull. Trim around the ends and sharply curved parts so it lies flat. Clamp or duct tape the cloth to the mold to stretch it. Trim the overhanging mat about an inch below the edges to allow for shrinkage when the resin is applied.

4. Mix resin and catalyzer. Work a section at a time. Pull up the mat, brush the resin over the gelcoat, lay the mat back over it, then brush the top with resin. Work the resin into the mat with the spreader or mohair roller. Work in resin till the white fibers and bubbles disappear. Work a section at a time from one end to the other. Don't let a section set before you apply the adjacent section. When you are done, clean your brushes with acetone and allow the first layer to set.

5. Lay a layer of 2-ounce mat strips over the first layer. Lay the strips at an angle the length of the hull till the whole surface is covered. Lay a second layer angled the opposite direction. Lay before the previous layer cures to improve lamination. Lay a final 1-ounce layer of mat as in the fourth step. Clean everything up.

6. Trim fiberglass that hangs outside the mold with a razor knife before the layers fully harden. If hardened, trim with a saber saw and sander. Start with coarse sandpaper to smooth the edges, then use fine sandpaper to finish. Allow the fiberglass to cure, then lift the boat off the mold. If you waxed it properly and used PVA compound, it should come right off.

7. Apply two layers of pigmented gelcoat to the outside of the hull. Allow to cure. Flip the boat over. Screw the cove molding halves together over the edges of the boat to make gunwales. The cove molding will bend to follow the curvature of the sides of the canoe.

8. Add ribs if the bottom is too flexible. Cut hardwood slats. Lay two or three of them across the bottom of the canoe. Glue with epoxy and weigh down so the ribs sit flat on the bottom. Allow to cure, then paint the ribs with resin, cover the ribs completely with a strip of 2-ounce fiberglass, then apply resin and pigmented gelcoat to match the bottom of the canoe.

9. Trim the thwarts with the draw knife and smooth with the sander. Screw the ends of the thwarts to the sides of the canoe. Apply marine seal around the screw holes. Do the same with the two seat support boards. Set the seats at a comfortable height so that your knees can rest on the bottom of the canoe while you paddle. Cut the seats to fit on top of the supports and screw them in place. Attach triangular-shaped wooden bow and stern deck plates to cover the ends of the canoe. Screw them to the gunwales. Stain and varnish all wooden parts with marine varnish.

Tips & Warnings

• Make sure the gelcoat is evenly thick all over, you add enough hardener to the resin and mix it well, and the gelcoat cures before laying up the mats.

• You may have to drill a hole in the mold and blow in air or water to separate the boat.

• Shake all acetone out of brushes before using. Do not drip acetone on uncured fiberglass or gelcoat.

• Wear respirator and eye protection when working with resin, gelcoat and hardeners or catalysts, or when sanding, trimming or spreading wet resin.

References

• Hand Lay-up of Fiberglass Parts on a Mold
• Fiberglass Mold Construction
• Bias Weave Fiberglass

Resources

• American Canoe Association
• United States Canoeing Association
• Paddling Net