How To Repair PVC Boats
Recommended solvent: MEK (methyl ethyl ketone). It is often available at paint, hardware or plumbing stores, sold as a cleaner for PVC pipes or lacquer thinner. For non-critical bonds you might substitute acetone.
1. Atmosphere: Glue with humidity less than 70%; and not in direct sunlight; Temp. 64° to 77°F is best.
2. Preparation: Gather rags, glue brush; solvent; timer with second hand or stop watch; make sure all the old glue is cleaned off; get your patch cut out, position noted and marked. It always leaves a neat tidy finish if you tape off the perimeter of the patch area with masking tape to avoid over glue.
3. Solvent Cleaning (3 times - to prepare the fabric for a chemical bond with the glue)
4. Scrub both sides (boat and patch or accessory) with MEK on a rag to clean surface. Be careful not to wipe the MEK on areas of the boat or patch that will be seen as MEK will make the fabric sticky and shiny. Use masking tape around the perimeter to minimize this. Wait 5 minutes after the first MEK wash.
5. Apply two more solvent wipes with 5 minute waiting time (timed) between them.
6. Apply a thin glue layer with stiff brush to both sides. Aggressively work it into the fabric with the brush. If it looks too thin, it is probably correct!
7. Wait five minutes (timed). If glue still looks wet, wait longer.
8. Repeat steps 6 & 7 (total of 3 layers with 5 minute open time between)
9. Wait 10 minutes after third layer of glue.
10. Join the surfaces during the next 10 minutes. Start from one edge and slowly lay the patch or accessory down onto the glued area.
Press out all air bubbles and wrinkles from the center to the edges. On deflated boat rub as hard as possible with smooth tool, e.g. the back of a large tablespoon - force air out from between boat and patch. Be careful not to scratch the fabric.
For davits and hard based accessories, deflate boat and press through from other side to make sure of adhesion. Wipe off excess glue with solvent.
If over 10 minutes or if glue has spots of white haze the glue has picked up moisture and you should try to "reactivate" it. With a clean rag wet the glue surface with MEK but do not rub the glue off (one quick swipe). Then assemble immediately. Press hard. For accessory on an inflated boat you can rub it down vigorously with a rag. Make sure there is no MEK on the rag when using it to run down the part or patch.
11. Wait at least 48 hours before use. Chemical bond will continue to strengthen over next 7 days. Don't be tempted to shorten the process.
12. Pressure test if you want to be sure. Blow it up to full pressure. Leave it overnight.
Humidity and Temperature Control.
Relative humidity must be less than 70%, preferably as low as 40%. Temperature 64° to 77°F. Bond strength drops very rapidly with heat or high humidity. Take your boat indoors. Don't even think about trying to glue on the dock or near the water or in direct sunlight. Professionals use a specially built, climate controlled room, and still don't attempt to work on a rainy day.
Mark out your patch or accessory perimeter where it will be glued on. Then use masking tape to tape off the area to ovoid getting MEK or glue on other parts of your boat during the repair process. This takes a little time but is well worth it in the end as the glue is hard to get off the boat after it dries and looks very messy when it dries and goes brown from the sun.
Apply glue with a paint or glue brush with the bristles cut short (1/2 to 3/4") so they are stiff. It must be natural hair (i.e. OK for lacquer); bound in metal not plastic; preferably with wooden or metal handle. Careful not to get glue on areas of your boat besides the repair area.
Old glue must be completely removed - solvent, sandpaper, scraping, grinding with a Dremel tool. Glue will not stick to old glue. Clean it off thoroughly. Be careful not to burn or melt the fabric if using a Dremel tool. Constant motion with the tool will prevent this problem.
If your boat has ever been protected with ArmorAll® or another silicone or petroleum based product, wipe the repair area well with MEK, follow the gluing instructions closely.
Pinhole size leaks in most PVC boats sometimes may be repaired simply by use of either Seam Seal or Air Seal liquids available at West Marine or on-line. You might be able to avoid a patch on the boat.
To find tiny leaks, take floor boards out, inflate boat hard. Put some liquid detergent in a bucket of water and with rag or big wash brush, scrub it all over boat. Keep watch for elusive, tiny bubbles. When you find the first leak, keep looking. You might as well fix them all at the same time! Remember, the number one cause of slow leaks is a poorly seated valve. Unscrew, clean. Make sure little rubber O-rings are good. They are the cheapest repair possible.
If patching, cut patches 1 to 2 " larger than tear in each direction and round the corners (a quarter makes a good template for the edges). Little one inch circles pasted over a pin hole won't last. Try to get the same fabric used by the manufacturer for your boat. The inside and outside surface may be different. If you can't match color, sometimes a cleverly shaped patch in contrasting color can be made to look like decoration instead of a Band-Aid. e.g. arrow, lightning bolt, even a new D ring if in right spot. Professionals often put one on each side to look like they came with the boat.
Inflate boat to apply accessories. Deflate to patch air leaks, even if very small. Air pressure will bubble the patch before glue sets.
Tip on how to repair small punctures with a syringe.
Sometimes tubes get punctured by a small wire or a noxious weed. In the southwest we have a nasty little thing called a goat head. It will puncture bicycle tires. It is easy to fix these kinds of holes without compromising the resale value of the boat.
Purchase a Syringe that has a #18 needle. (available at veterinarian and feed stores) Place the needle through the puncture hole. Position the boat so that the needle is at the lowest point. Most of the time the boat must be inflated so that the inside of the boat is not glued together, or that the needle punctures the other side of the boat. It is important that the glue be allowed to puddle up around the hole so that air pressure can force the glue out of the hole and help seal it up. It is also important to be able to remove the plunger and leave the needle in place in the boat. In this way the plunger can be filled several times to insure enough glue in the affected area. Use a paper cup to mix a small amount of glue, and then pinch the top of the paper cup to make a spout. The glue can be poured from easily and slowly into the top of the syringe while holding a finger on the needle end. Replace the plunger, and allow air bubbles to rise to the top before placing the syringe and the needle back together. This is a fairly messy operation. Gloves are recommended. Be careful to hold the needle and syringe together as the plunger is operated. It is easy for them to separate and spray glue on the boat. If this happens have a rag to clean it up quickly before it can do any damage. When pulling the needle out twist it so that the needle itself helps drag some glue into the fabric to help seal the hole.
Do Not Smoke! Glues and solvents are flammable. Use in a well ventilated area. Fumes can be overwhelming. A carbon filter respirator is recommended. MEK solvent smells, but is relatively safe. Always wear safety gear as recommended by the manufacturer of glue, solvent, accelerator, etc.