Apply Heat
If you’ve worked quickly, your hot water bag will still be warm. If the water has cooled too far, pour it into a cook pot, reheat it to lukewarm and fill the bladder again. Even on a cold day, you shouldn’t use a bag that is hot to the touch—if you do, your resin will cure too quickly and may develop cracks. Water near your body temperature will be warm enough to do the job.

Put the water bag inside the kayak over the patch, and sit back to wait. The plastic on the inside of the hull should keep the resin from contacting the hydration bladder. Cover the bag with a fleece sweater or sleeping bag to help contain the heat. If the hull and bag are insulated, this technique will cause the polyester resin to cure even with air temperatures near freezing.

While you’re waiting, clean up your work site and double-bag the fiberglass waste. Monitor the hardening process by putting your hand on the hull near the repair. It should not be hot to the touch. If the patch is giving off too much heat, remove the hot water bag and let the repair continue to cure on its own, insulating it with the fleece sweater again. Give the patch 20 minutes to cure, and take a peek. Remove the hydration bladder and peel up the plastic. If the patch is hard and dry, you’re done. If it’s still sticky, add more heat. Reheat the water if you need to.

Once the patch is fully hardened, you can remove the covering layers from both the inside and the outside. The outer patch may be a bit rough due to seeping of resin underneath the plastic. Use some coarse sandpaper to take down any major bumps. Don’t worry about cosmetics—you can do a nice gel-coat repair when you get home (see “Gel-Coat Repair for Mortals,” by Brian Day, SK, Feb. ’06). Make sure that the patch is smooth enough on the inside that it won’t damage your dry bags. Sand the inner patch to take down any rough spots if necessary. Pack away the last of your waste materials and relax—you’re back in the paddling business.

Special Situations
Certain areas of a kayak’s hull may be difficult to reach for internal patching. The most obvious spots are underneath the seat and at the extreme ends of the hull or near bulkheads. In these spots, it’s probably best to apply your patch to the outside of the hull. You’ll also have to apply heat from the outside, and you may have difficulty backing the patch with a piece of plastic. The resulting repair will be cosmetically unattractive, but structurally sound. Proper repairs can be completed at home or by a professional fiberglass repair shop.

Practice Makes Perfect
Field repairs on fiberglass kayaks are easy to do if you have the right materials and know the right tricks. A bit of practice with fiberglass materials will improve your results when it counts and boost your confidence—and even cold-weather repairs are possible if you apply a little heat to the job. Take the time to put together a basic fiberglass repair kit and learn how to use it. One day, it might help you or a paddling partner make it home.

Sequence of Repair
1 Heat water, fill hydration bladder
2 Clean, dry and prep hull
3 Warm tape, resin and hull
4 Tape plastic to hull
5 Cut out patches
6 Mix resin
7 Wet out patches
8 Apply patches to inside of hull
9 Cover with plastic and water bladder
10 Wait 20 minutes
11 Remove plastic, sand inside and outside of hull

Fiberglass Repair Kit Contents
Waxed Polyester Resin
Catalyst
Fiberglass Mat
Fiberglass Cloth
Disposable Paint Brushes
Stirring Sticks
Paper Cups
Plastic Sheet or Freezer Bags (1-gallon size)*
Duct Tape*
Small Scissors*
50-Grit Sandpaper
Latex or Nitrile Gloves*
Watertight Container
*These items need not be specific to your fiberglass repair kit. They might be a part of your first aid kit or general camping gear.

Brian Day has been paddling, breaking and repairing sea kayaks since 1992. He is a Level 3 BCU sea-kayak coach and lives in Madison, Wisconsin.