Repairing your inflatable dinghy.
Before you can repair your inflatable, you need to know about the materials and construction of your inflatable. The majority of all inflatables used for boating consist of a substrate and a coating: the substrate provides the strength and the coating provides the waterproofing. Common coatings are elastomers, with trade names such as Hypalon or neoprene, or co-polymers, such as PVC. The substrates are likely to be either polyester or nylon. So before attempting any repair on your inflatable, you must know what type of materials you are repairing, because the glues that bond to Hypalon, for example, will not work on a PVC material.
Also before you tackle the repair check to see if there is any air escaping from the valve. Valve leaks are usually caused by sand or grit jamming the mechanism, or by a missing o-ring necessary for an airtight seal. Use the inflatable air pump to blow out foreign particles from the valve and, if that doesn't solve the problem, have a new valve installed either by yourself if you feel confident or a professional.
Most leaks, are simply very small hole punctures or tiny cuts that you can repair easily. Always rely on kits from the manufacturer of your dinghy, which can be found at most marine hardware stores or your inflatable dealer. Most factory repair kits include the proper glue (and a catalyst or accelerator), a solvent for cleaning and pre-softening the material, and patches of various sizes of fabric to use as the repair. You will also need some 100 grit sandpaper, masking tape, paper cups, scissors and an old spoon. So get these items around you before starting the repair.
Finding the leak is your first problem, because you have a lot of inflatable surface and a leak that is probably no bigger than the head of a pin. Using wash up detergent in water and, with your dinghy fully inflated, brush this soapy water over the entire area. Soap bubbles will start to generate identifying the leak. Mark the spot with a felt tip pen, and carry on looking for any other leaks because there maybe more than just one!
With the patch in place, trace around it using a pencil or chalk ( not the felt pen as it will be seen for ever more!) Use masking tape around the patch to prevent the glue going everywhere. It also keeps the repair looking neat and tidy. Make sure the fabric of the inflatable is now completely dry.
Before applying the glue and patch, use the 100 grit sand paper to rough up the area around the hole. This will help the glue to adhere to the fabric. Clean it up with a solvent. Following the repair kit instructions use the two part glue on the surface of the inflatable, leaving it as the kit suggests, probably for a few minutes. Then apply the patch. This is where you use the old spoon. Use the spoon to drive out any trapped air which will prevent a seal between the patch and dinghy surface. Now this next stage involves a bit of creativity on your part. To ensure a really good seal you need to devise a method of keeping these two bits together. Some people use a large stone or brick on the patch while it cures. Others, and this is my favourite, use two pieces of plywood with plastic over them, four clamps, and the inflatable material and patch compressed between them until the glue sets. I tend to leave it 24 hours to be sure.
Once set, remove all these clamps etc. and inspect the new repair. Use some luke warm water to clean around the area and inflat your dinghy. Wait to see if she stays inflated.