Imagine that you’re paddling your fiberglass kayak on a long trip in a remote area. On your way in through the surf, the bottom of your boat meets with an unseen rock—Wham! One minute you’re paddling a seaworthy boat, the next you’re taking on water. You’re miles from your car, and something needs to be done to keep the water out. A hasty patch of duct tape might do the trick for a while, but for a durable and reliable repair, there’s only one solution—polyester resin and fiberglass.

Resin needs a warm environment to cure in, so if you’re traveling in cold weather, you may wonder how you’ll get the resin to harden. Adding a little outside heat is the answer. Armed with a hydration bag full of hot water, you can put a solid patch onto the hull of your boat, even in adverse conditions.

You needn’t be intimidated by the prospect of working with fiberglass. Rudimentary fiberglass work is straightforward and easy to do. The polyester resin you’ll use for repairs is fairly tolerant of imprecise mixing and variable temperatures. It’s worth practicing with fiberglass a little bit at home to develop a familiarity with the process, but you don’t need to be an expert to make a quality repair.

Materials Compatibility
Polyester resin is easy to work with, but it’s not compatible with some other types of resins. What this means is that if your kayak was built with epoxy resin, polyester won’t stick to it. Your patch will pop off. Polyester resin will stick to hulls made with vinylester if you prep the surface with sandpaper very aggressively, but it still isn’t as safe a bet as polyester repairs on polyester kayaks.

The good news is that virtually all fiberglass kayaks use polyester resin in their construction. If you have a Kevlar or carbon-fiber kayak, it’s more likely that one of the other resin types was used. Check with the manufacturer of your boat to determine its resin type. Polyester won’t stick to epoxy, so repairs to epoxy or vinylester hulls should be made using marine epoxy resins. (This type of repair falls outside the scope of this article.)

Epoxy will stick to polyester, but if you need to make subsequent repairs in the same area with polyester or want to restore the gel-coat, the epoxy must be removed. Epoxy requires precise mixing to ensure a proper cure and is usually slower to cure than polyester resin. All of these things make epoxy resins ill-suited for use in field repairs for fiberglass kayaks.

Safety Precautions/Environmental Concerns
Polyester resin is not healthy stuff. Avoid getting it on your skin or breathing its vapors. You’re unlikely to be carrying a respirator in the field, but take whatever precautions you can when doing your repair. Wear latex or nitrile gloves from your first aid kit. Set up your workplace where there’s a breeze, and stay upwind of the vapors. The materials are also toxic to the environment, so pack out any waste from the fiberglass repair process, regardless of how small it is. Never burn your fiberglass waste—if you pack it in, pack it out.

Repair Kit
The materials for a fiberglass field-repair kit can be found at your local hardware store and supermarket. Polyester resin usually comes in metal cans that are quart sized or larger—more resin than you’ll want to take on most trips. You’ll want to take a smaller amount, but small metal canisters are hard to find, and the polyester will melt most plastics. At many marine and auto supply stores, you’ll find a Bondo fiberglass repair kit. It comes with eight ounces of waxed resin—enough for a basic field-repair kit—in a bottle made of a special resin-resistant plastic. The kit also includes hardener and woven fiberglass cloth. Chopped-strand fiberglass mat can often be found near the kits or at the hardware store.

I use a half-gallon, wide-mouth Nalgene bottle as a materials container for my repair kit. These bottles will fit behind the seat of many kayaks, and they are absolutely watertight, so they’ll keep items like sandpaper from getting damp.