Cockpit Coaming (8 Hours)
There are many methods of building a cockpit coaming and making a carbon fiber coaming is certainly one of the hardest, but it is an achievable project for the home builder. I like to build mine in four steps.
The first step is to make the foam mold that will be used to produce the coaming. Make sure that your opening is sanded smoothly and looks fair. Check this fairing with the cockpit cutout template used to make the recess. Any type of foam can be used to form a coaming, but I used expanding spray foam, because it was what I could get in town. I sprayed a bead of foam around the cutout and waited for it to set-up and dry. Once dry, I roughed it into shape with a pull saw, and then roughed it closer with a flat and curved surform. The final surface was shaped with 40 grit sandpaper. After the sanding cover the foam with clear packing tape. The tape acts as a mold release. If you want a perfect mold, spray the foam with sanding compound, sand, shape, cover with four or five layers of wax, and the PVA mold release.
After shaping the foam, turn the deck over, rough up the area around the cockpit opening with 60 grit sandpaper so the fiberglass will bond with the deck. Next lay-up a couple of layers of glass running from the inside of the deck to the coaming rise. At this point, don’t worry about forming the coaming lip. I like to dye the epoxy black at this step. This results in a rich black color under the coaming lip. I use 2 layers of 5 ounce tight weave to form this initial lip. After this has set-up, trim this riser even with the top of the foam.
The third step is the hardest. This step is laying up the rest of the riser and the coaming lip. For those skilled in glassing, you can also glass in a drop at this point to hold the straps for the backrest. I passed on doing this, and will try something slightly different. Make sure the surface is clean and that the packing tape is holding and then start wetting-out 2.5″ pieces of glass about 10 inches long. Wet these piece out on a flat surface covered with plastic. These should all be pre-cut or you should have an assistant there cutting the pieces as you go. These strips wrap from the coaming lip on top of the foam down around the bend to the fiberglass riser formed in the last step. Many of these will start to peel up as you continue the project, don’t worry about this yet. Just try to get everything to lay correctly. I use a lay-up of 4 layers of 5 ounce tight weave, 1 layer of epoxy mat, 1 layer of 5 ounce tight weave, 1 layer of 5 ounce carbon fiber, and finally, 1 layer of 6 ounce.
stay there while they harden. To do this, put pieces of peel-ply over the coaming. I use strips 4″ wide by 5″ long. While applying the peel-ply rub the pieces smooth and make sure that they are fully in contact with the surface of the glass. Any air bubbles under the peel-ply will create extra work for you later. Around the tighter bends of the cockpit, some bubbles are almost unavoidable. After the coaming is covered with peel-ply, it’s time to tape. Wrap the entire coaming lip with masking tape, making sure that the glass is pushed down to the foam mold and the fiberglass riser. Pull the tape tight and work out any bubbles you see in the peel-ply. After this is finished, allow the coaming to dry.
The next day, remove the tape and peel-ply, measure a one inch coaming lip around the cockpit opening, and cut to the outside of this line. Use sand paper to dull the sharp edge and bring the coaming to the line.
The surface is now ready for final sanding. Work on sanding out any bubbles or creases created by the tape and peel-ply.
Wooden Recessed Deck Fittings (Optional)
To build recessed deck fittings, you’ll need a router, template guides, and you’ll need to build a router template. For my router template (see the pdf file), I cut the template out of 3/4″ plywood 7/16″ beyond the outside dimension of the final fitting opening. This allowed me to use a 5/16″ template guide with a 1/4″ bit to cut the lip of the fitting that came up through the deck, and it allowed me to use a 1/2″ cove box bit with an 1 5/8″ template guide to cut the recess itself.
There are numerous ways to do this, but I screwed the template to the wood (3/4″ cedar) I was using and cut out the required routes. It helps to have two routers during this operation.
The template I designed snuggly fits 1 1/8″ wide Valley fittings. You can substitute stainless steel rods for these fittings.
After making a couple fittings, I changed my mind and decided to to leave the lip off the fitting and just fit the recess under the deck. This allows you lay a layer of carbon fiber into each fitting for appearances and have it end flush with the deck.
Once the fitting blanks are cut, use a power sander to round the bottom of the fitting to a nice smooth shape.
To attach the fittings to the hull, first cut holes into the deck using the proper size template guide and the template used for cutting the fittings, and then use thickened epoxy, colored purple or black to match the dyed kayak or the carbon fiber, respectively. Then lay a layer or two of glass over the backside of the fitting. When the glass is cured enough to drill, drill a hole for the Valley fitting, coat the hole with epoxy, insert the fitting and cover the nut with thickened epoxy to make sure there is a good seal.
Then lay up the carbon fiber on the outside of the fitting.
Glass and Carbon Recessed Deck Fittings (5 hours for 18 fittings)
After building the wooden recesses for my kayak, I decided to change plans and go with a fully glass recess. Building these requires much less work. First cut the holes in the deck for your recess, round the cuts with a file and sandpaper. Dye the exposed surface.
After the holes are cut, a mold must be built for each recess. This is easily accomplished using chunks of green foam that is used for floral arrangements. Cut a block of foam that is about 1/2″ larger than the hole for the recess, and about 1.5″ deep. From the outside of the deck, push the foam through the hole you cut. Keep pushing until the foam has come through the opening 1/4″ deep. You’ll find that pushing the foam through the hole is extremely easy and it perfectly matches the required shape.
When the foam has been pushed 1/4″ deep, tape it in place, and use your fingers to round the corners of the foam. Then use your gloved finger to apply some PVA mold release to the foam. It’s best to use, at least, two coatings, because the foam may absorb the first and second layers completely. As soon as you have a coated surface, the fittings are ready for glassing.
Mix up a batch of thicken epoxy. A mix of fumed silica and mircoballons will ensure a light and no sag mixture. Gently spread the mixture over the PVA coated foam making sure not to tear the PVA. The key point here is to spread enough of the mixture to allow the fiberglass that you’ll lay up next to easily curve from the mostly flat deck around the curved fitting. The joint between the deck and the foam is the most important location to think about. You can have this mixture be a final outside surface, but it’s best to use purple micro balloons, which will blend in with the blood red dye or use black epoxy pigment to make the mixture black.
Next cut out 6 4″ by 4″ patches of six ounce glass for each deck fitting. Wet these out on a plastic coated surface and then lay them over the foam mold trying to avoid air bubbles and moving the thicken mixture around a bit to arrive at a smooth surface. Cutting all the patches at ounce is easiest and allows the thicken epoxy to set-up slightly, which makes it easier to work with.
Once cured, dig as much of the foam out of the recess as you can. Then use cold water from a hose to remove the rest of the foam and the PVA. Acetone can also dissolve the foam, but make sure your epoxy is completely cured before trying this, because acetone can weaken uncured epoxy.
Next is to mask using masking tape around each fitting, make another batch of thicken epoxy and fill in any imperfections that you may encounter. Then lay a layer of wet 6 ounce carbon fiber into the fitting from the outside of the hull. Once the carbon fiber cloth has had hardened enough to cut with a razor. Cut into it removing any excess that rises over the masking tape and above the deck.
Drill a hole, attach a Valley fitting, and use thicken epoxy to cover the nut on the inside of the hull.
This method would also work using just a stainless rod instead of a Valley fitting. For this layup, you’d have to either settle on the finish provided by the thickened epoxy, or lay a layer of carbon fiber directly against the foam mold and make sure no bubbles are formed. For this method, after PVA has been applied push the stainless rod through the foam, making sure it is directly against the deck. Then lay the glass and thickened epoxy over the foam and steel rod. To make sure the rod doesn’t spin, bend the end of one side 90 degrees before pushing it through the foam.
Notes: Jay Babina suggested using ping pong balls cut in half for round recesses. The balls stay in and are painted black after glassed and gooped into place. Brian Nystorm writes, “Molding deck fitting in ice-cube trays. I’ve seen them in various cavity shapes and some trays are polyethylene, which epoxy won’t bond to. It would seem like an easy way to easily make consistent deck fittings.”
Skeg Box and Blade (5 Hours)
The skeg box and blade for this kayak is built completely from fiberglass. To do this, a mold must first be constructed. A good material for the project is two pieces of 1/4″ luan plywood sandwiched together to become a half inch mold.
First, shape the skeg box mold to the desired outcome, account for the thickness of the hull in your desired depth, and then leave enough wood on the bottom of the mold to make for easy extraction after you’ve finished the lamination step. Sand the edges of the skeg box mold to the radius of a number two pencil. Wrap this with packing tape, trying to get the tape to lay down as tightly as possible over the edges of the skeg box.
Next, cut out the skeg box opening in the bottom of the hull. For this kayak, it makes sense to offset the skeg box, so the built-in skeg isn’t distorted from the new skeg. I offset the skeg box from the center one inch. Make sure that this is even or you could run into problems with performance.
Once satisfied with the skeg box cut-out, apply a layer of paste wax. Allow it to dry and apply a second layer.
While the paste wax is drying, lay a layer of glass through the opening that you just cut. To make it lay right and wrap nicely, tape dry glass to the outside of the hull, run it through the hole and then lay it down on the inside. Wet this glass out.
When the skeg box mold is dry, insert it into the hull from the bottom. Make sure the depth is correct, and then tape it into place. I used saran wrap covered with tape, and then taped the mold vertically with several pieces of tape. Coat the bottom inch with a layer of thickened epoxy (microballons and silica). Pull the fiberglass piece from the bottom onto the thickened epoxy and force some thickened epoxy into the space between the glass and the open wood for your cut through the hull, then lay a couple of layers of six ounce around the skeg box mold and into the hull of the kayak. The thickened epoxy will help hold this glass in place and it will provide a nice radius for the glass to curve around. Work this area so that you have nice smooth curves.
Now, you can go off and cut out the remaining glass for the rest of the skeg box while you wait for this first layup to harden enough to support the skeg box mold vertically.
The lay-up schedule that I use for the skegs is two layers of 6 ounce glass, 1 layer of epoxy mat, followed by three layers of 6 ounce glass, and one piece of 6 ounce 2 inch tape for a final layer over the top of the box. You’ll need to cut enough glass to cover this lay-up. Keep in mind that smaller narrower pieces bend around the top easier.
When the first layers of glass are set-up, mix up a batch of thickened epoxy and apply it smoothly over the rest of the skeg box mold. Then lay a layer of plastic on your work bench and wet-out all the pieces of glass you’ll use for the skeg. Then start laying up the skeg box. Make sure that all the layers are tight to each other to avoid air bubbles. When done, lay a layer of glass tape over the top and and, optionally, cover the whole box with microballlon thickened epoxy for easy sanding after the box is curred. Cover this with pieces of peel ply. Peel ply doesn’t like to bend in several directions, so make sure to use small narrow pieces for the boxes top edge.
After the glass has cured, peel off the peel ply and you should have a nice surface which will need only a little sanding to finish.
While you’re waiting for the box to cure, you can build the skeg blade. I use three layers of mat and four layers of 6 ounce glass to make mine. This will end up with around a 1/4″ thick blade. Making this is easy. Lay a piece of plastic wrap on a flat surface, lay up the fiberglass, then lay a glass window covered with plastic over all the fiberglass and weigh this down. I colored my blade black by using an epoxy dye.
Installing the cable, blade, and control box will be covered in the next installment.