The damaged area of your kayak has to be dry and free of salt residue to get a patch to stick. This means getting out of the rain and under a tarp if you’re traveling in wet conditions. If possible, rinse the damaged area with fresh water. Dry the boat thoroughly inside and out. This can be a real challenge in some conditions. You might have to add heat to the boat to help the drying process.
You don’t want to risk burning the kayak by using the flames of a stove or campfire, so the safest way to do this is with a hydration bag filled with hot water.
Use your camp stove to heat a couple liters of water. Seawater will work fine if fresh water is scarce—just remember to rinse the bag before using it for drinking water again. Pour the water into the hydration bag once it’s hot to the touch but not boiling. Both MSR Dromedary Bags and Cascade Designs Platypus bladders are approved to hold hot liquids. Both are also available with wide openings for easy filling. Use care when transferring the hot liquid so that you don’t scald yourself! Set the bag inside the hull in the area to be dried.
Once the kayak is dry and clean, you’ll need to sand the inside of the hull where the patch is to be applied. You want a rough surface for good adhesion, so use 50-grit paper and be aggressive. Make sure that you sand an area that’s larger than the patch you intend to apply. After sanding, blow or wipe the resulting dust out of the way. In a more controlled environment, you would wipe the site of the repair with acetone or denatured alcohol, but there’s really no need to go to the trouble of carrying these solvents in your field-repair kit.
You’ll be applying duct tape to the hull of the boat in the next step, but you may find that your tape won’t stick to a cold surface. The hydration bladder full of hot water again comes in handy. You can warm the boat by placing the bag on the damaged area. Try not to get the outside of the hydration bladder wet, and avoid getting water on the hull of your boat. Your kayak needs to be dry for the repair to cure properly.
Leave the bag in place long enough to warm the kayak’s hull. The elapsed time will vary depending on the outside temperature. You can throw a sleeping bag or fleece sweater over the hull and water bag to speed the process. It also helps to heat up the duct tape to make it stickier, so put it inside your clothing layers or on top of the water bag. Do the same with your bottle of polyester resin. In cold temperatures, resin becomes more viscous and more difficult to paint onto a patch. Once the hull and tape are warm enough to stick, remove the bladder and wrap it in the sleeping bag or sweater to keep it from cooling rapidly.
Use the tape to apply a piece of plastic (cutting up a large Ziploc bag works well) to the outside of the hull over the area to be patched. The plastic is to keep resin from seeping through the damaged area of the hull. Make sure that the plastic covers the repair area and overlaps out onto the undamaged portion of the hull.
Turn the kayak so that the area to be repaired is down—you’ll avoid having resin run across the hull. You may need to use some ingenuity to get the kayak to stay in this position. Consider digging a hole in the beach across which you can set the boat, or propping it up on driftwood or boulders. You don’t want the kayak resting on the area you’ll be repairing since that would cause a flat spot in the boat. As you position the kayak, you may want to wrap a layer of insulation around the outside of the hull in the area of the repair. A sleeping mat, fleece sweater or sleeping bag can be used to insulate the hull and keep the patch warm.
Cut a piece of chopped-strand fiberglass mat that is slightly larger than the area to be repaired. Mat is excellent for repairs because it holds a large amount of resin. A high resin-to-glass ratio is considered bad form in kayak manufacturing, but it works well for making a stiff, waterproof patch in the field. Cut a second piece of mat that’s about a half-inch larger than the first. If you’re repairing a large hole or tear, a third patch of woven fiberglass cloth, cut slightly larger than the second patch, will improve the strength of a patch.
Put on a pair of protective gloves and mix up your resin. Follow the directions printed on the resin or catalyst. These typically call for 15 drops of catalyst/hardener for each ounce of resin, which is a ratio approaching two-percent catalyst. This ratio is a good one for field repairs. Waxed resin has a wax additive that rises to the surface of the repair as it cures. This wax creates an oxygen barrier that makes the resin cure with a hard, dry surface. Using unwaxed resin may result in a sticky patch.
Mix up enough resin to complete the repair. Three or four ounces should do the job for a small patch. You’ll need a container to mix it in. I put several eight-ounce paper cups into my repair kit for mixing. These are the same cups that you would find at a coffee shop, convenience store or grocery store. Both waxed and unwaxed cups will work. If you packed a stirring stick, great; if not, use a smooth stick from the beach.
Set a Ziploc-type plastic bag on a flat and firm surface, and begin “wetting out” your patches. Paint a little resin onto the bag, then lay one of the precut pieces of glass mat onto that resin. Use your paintbrush to work the resin into the glass fabric until it becomes translucent. You’ll have to add more resin as you work to get the patch completely wetted out. Follow this process for each of your patches. Working with the resin will be much easier if you have prewarmed it by tucking it in with the hot water bag. If the resin is cold and super-thick, you can still complete the repair, it will just be a little harder to work the resin into the glass patches.
Once your patches are wetted out, paint a layer of resin onto the inside of the hull where the patches will be applied. Place the smallest patch onto this area, and paint it with additional resin to make sure that it’s fully saturated and adhered to the hull. Use the brush to work any air bubbles out of the patch. Repeat the process with the second patch and the woven glass if you have chosen to use it. Once you’re satisfied that the complete patch is fully saturated, cover the repair with the plastic bag that you used for wetting-out—sticky side down.
