Building a Carbon Fiber
Greenland Paddle

By Duane Strosaker

(updated 5/30/09)

From plug, to mold, to paddle.

Greenland paddles are traditionally made of wood, which has been a good material for making them. But the carbon fiber Greenland paddle made by Superior Kayaks, Inc. intrigued me, so I ordered one. When I opened the package, I was awed at the beauty of the paddle. The modern material wonderfully complimented the traditional design. Being the home builder I am, I just had to build my own carbon fiber Greenland paddle.

Building this paddle isn't much different than building a composite kayak. Like the deck and hull of a kayak, the pieces of the paddle are molded and then assembled at the seams, which is a construction technique found in almost any fiberglass manual. But before any molding can be done, a plug has to be carved, and from it, a mold is formed.

I don't know how Superior Kayaks, Inc. is able to beautifully assemble the molded pieces without any apparent (as far as I can see) composite reinforcement on the outside of the seams and still make the paddle so strong. I wasn't about to cut into a perfectly good $340 paddle (now $475 and worth every penny) to find out how they do it, so I settled for making my paddles using the common technique of composite reinforcement on the outside of the seams, and they turn out pretty nice.

Building the Plug

The carved blade half.

Building the plug starts like carving any wooden Greenland paddle, except that only one side of one blade and the loom is made. The other side is flat. Make sure that the edge on each side of the blade is exactly like the opposite side so that the two halves of the molded carbon fiber blades will meet perfectly at the seams when they are joined back to back. Also, avoid making sharp curves that the carbon fiber cloth will have troubles forming around.

The directions I recommend for carving a wooden Greenland paddle are by Chuck Holst at the Qajaq USA website. Matt Johnson has an online video on how to carve a wooden Greenland paddle using Holst's directions. Brian Nystrom has a book on building Greenland paddles that you can order online at www.greenlandpaddlebook.com. My own Greenland paddle specifications are at this link.

The plug and flange.

The plug needs a flange, which is simply a flat piece of wood that is epoxied to the blade half. Be sure to read and study the user manual for the brand of epoxy being used. Before epoxying the blade half and flange together, coat them with epoxy and sand them smooth until they are shaped perfectly.

After the epoxy has cured, apply five coats of Johnson paste wax to the plug (and flange) so the mold won't stick to it. Then, for the same reason, brush on a coat of PVA mold release and allow it to dry before building the mold.

Building the Mold

Layers of fiberglass over the plug.

The mold is built by applying layers of fiberglass to the plug. Along the sharp corners of the plug, which is between the blade half and flange, apply a fillet of epoxy thickened with colloidal silica filler, because the fiberglass cloth won't bend that sharp. Apply a layer of six ounce fiberglass, let the epoxy cure, and then add two layers of 1 1/2 ounce chopped-strand fiberglass mat to stiffen the mold. Make sure the chopped-strand mat used is compatible with epoxy resin.

The plug and mold.

After allowing the mold to cure, pull it off the plug. Then prepare the mold like the plug was with five coats of paste wax and one coat of mold release. To prevent the mold release from forming a puddle in the mold, set the mold vertically on the loom end, until the mold release is dry.

Now that you are done with the plug, hang it up in your home as art.

Molding the Blade Halves

The lay-up wetted out and squeegeed on wax paper next to the mold.

Because the mold is a small and curved area, wetting out the lay-up with epoxy is easier on a sheet of wax paper on a flat surface. The lay-up I prefer is four layers of 5.8-ounce plain weave carbon fiber, which results in a finished paddle weighing approximately 20 ounces and having the same amount of flex as Sitka spruce. Carbon fiber also comes in twill weave, which looks nicer and actually forms slightly better around curves, but it doesn't hold up as well as plain weave to the hands pressing it into the mold. Wet out the first layer of carbon fiber, put the next layer on top of it, wet it out, and continue until all four layers are wetted out. Then use a squeegee to remove the excess epoxy.

The lay-up in the mold after the initial trimming.

The lay-up is peeled off the wax paper and placed in the mold with the smooth/wax paper side of it facing down. Trim the excess lay-up with scissors so that only around one-half-inch of it is sticking up from the mold. Be sure to press the lay-up into the mold firmly and evenly, and press out all the air bubbles between the mold and lay-up. Use acetone to clean the epoxy off the scissors and squeegee.

Final trimming with a razor blade before the epoxy has fully cured.

Before the epoxy has fully cured, the final trimming of the lay-up in the mold is done with a razor blade held flat against the flange edge. This step must be done when the epoxy has stiffened some and is still slightly sticky. Depending on the type of epoxy used and the room temperature, reaching this curing state can take from one to six hours. Use a single edge, steel backed razor and keep it angled toward the flange during the cut to prevent the lay-up from being pulled off the mold.

Let the epoxy cure at least eighteen hours before popping the blade half off the mold. The blade half pops out easily by just bending the mold. Wash the blade half with water to remove the mold release from it. Four blade halves are needed for one paddle. Between each blade half, wash the mold with water, dry, and apply a coat of paste wax and mold release.

The blade halves won't be perfect. Sometimes the razor drifts downwards and cuts the carbon fiber slightly below the flange. After the blade halves are epoxied back to back, these small voids in the seam can be filled with thickened epoxy and sanded smooth. Also, occasional spots on the outside surface of the blade will have tiny voids where air was trapped between the lay-up and mold. As you continue building the paddle, fill these voids with epoxy and sand smooth.

Assembling the Four Blade Halves

Clamping the blade halves together with rubber bands.

Slightly sand the seam edges smooth, apply epoxy to the them, and clamp the blade halves together with rubber bands until the epoxy has cured. Before the epoxy begins curing, it is important to make sure the seams are straight and that there is no twist in the blades.

Reinforcing the seams with 3/4 inch bias-cut carbon fiber strips.

Lightly sand 1/2 inch to each side of the seams. Then use 3/4 inch wide strips of bias-cut carbon fiber to reinforce the seams. This bias-cut is done diagonally at a 45 degree angle across the weave, and it is stronger because each strand crosses the seam. More importantly, the bias-cut forms easier around the edges of the blade. You may be tempted to use composite tape, but it won't form well around blade edges. Use a brush to apply epoxy to the seams, and then lay the strips on top. Apply additional epoxy to the strips to fully wet them out by dabbing with a brush. When the epoxy has cured, apply two coats of epoxy over the strips to fill in the weave. Sand the edges of the strips to feather them smoothly into the molded blades. Try to avoid sanding into the carbon fiber in the molded blades.

Miter box.

Use a miter box for a straight cut at the loom end of each piece, which will be the center of the paddle.

Closed-cell foam plugs (which serve as silencers) before being inserted into the looms.

While the perfect Greenland stroke is silent, not every stroke is perfect, and air ventilating behind the blade makes a scratching sound, which will travel loudly through a hollow paddle. To make the paddle as quiet as a wooden one, insert closed-cell foam plugs into each loom just before the root of the blade. To help keep the plugs in place, coat the sides of them with epoxy. Then after the plugs are inserted, point the looms straight up, and drop some shredded fiberglass and epoxy on top of the plugs to form bulkheads.

Assembling the Center of the Paddle

Epoxying the two ends together at the loom.

The center of the paddle is assemble on a board to make sure the paddle is straight and not twisted. I make the board perfectly flat by adjusting how it's nailed to an old strong-back. On the board mark a straight line with guidelines to each side that match the thickness of the loom. Also mark the center of the blades to line them up with the centerline on the board. Using small pieces of wood, raise the tips of the blades equal to a distance half the width of the loom. Use a level to check for any twist in the blades.

Join the two ends of the paddle temporarily at first by sanding to each side of the seam, coating the seam with epoxy, and applying a one inch wide and two inch long piece of carbon fiber to reinforce the top two-thirds of the seam. Before the epoxy begins curing, make sure the paddle is straight and not twisted. Allow the seam to cure 24 hours before gently handling the paddle. Double check that the paddle is straight and not twisted. Now is the time to bust the seam and rejoin if necessary.

The center seam wrapped with carbon fiber, wax paper, and masking tape.

When the seam is ready to be fully reinforced, sand to 1 1/2 inches of each side of it. On wax paper wet out a three-inch-wide strip of bias-cut carbon fiber long enough to wrap the loom four times. Peel the carbon fiber off the wax paper and wrap the seam. Then wrap the carbon fiber with wax paper and masking tape in the same direction that the carbon fiber was wrapped. Allow the seam to cure for three days before applying any pressure to the paddle.

Finishing

Sand the paddle smooth with 220 grit sand paper. Then apply a thin coat of epoxy. After the epoxy has cured, roughen the texture of the paddle for the perfect grip by wet sanding with 400 grit and rubbing it with wet "0" synthetic steel wool. It is not necessary to finish the paddle with varnish.

Materials for the Plug, Mold and Paddle

Wood for plug and flange, 3/4 inch thick, 6 inches wide, 9 feet long
Fiberglass, 6 ounce, 50 inches by 10 inches
Fiberglass chopped-strand mat (compatible with epoxy resin), 1 1/2 ounce, 50 inches by 20 inches
Carbon fiber, 5.8 ounce, plain weave, 50 inches wide by 3 yards
Epoxy resin and hardener, 2 quarts
Colloidal silica filler for epoxy
Closed-cell foam, 4 inches by 2 inches by 1 inch
Johnson paste wax
PVA mold release
Wax paper
Razors, single edge, steel backed, at least 4
Acetone for clean-up of brush, scissors, and squeegee
Sand paper, 60, 100, and 220 grit
Synthetic steel wool, "0" coarseness
Latex gloves to protect hands from uncured epoxy