Perfect patches

Practical: DIY

Necessity is the mother of invention, Christine Muir and Keith Hunt discover when their dinghy is stolen and damaged.

While in Panama our inflatable dinghy was stolen off the davits — despite it being attached by a stainless-steel cable and us asleep on board!

On that same night, two other dinghies were also stolen — the police believe that the raid was organised to harvest 15hp outboard engines (which are very popular with the locals). The irony is that the only reason our outboard cover was not hiding the 15hp was because Keith had been trying to improve its reliability!

Once they removed the engine, the thieves apparently had no interest in the dinghy and threw all our ancillary equipment overboard, which comprised oars, seat, storage bag, lifejackets and flares, anchor and chain, etc. They then tried to sink the RIB by inflicting 14 stab wounds and cut the starboard tube away from the transom. The dinghy was spotted by an alert sailor as it drifted through the shipping channel, and it was subsequently returned to us by the friendly and helpful Panamanian authorities.

Only option

We were unable to source a replacement dinghy without a long delay, so our only option was to try and repair the tubes. We drained the small amount of water that had entered the tubes and did our best to inflate them and left the dinghy on deck to dry while we figured out how best to repair so many holes. Most of them were about 1½” long — we were glad that we hadn’t disturbed the thieves or the knife might have been used on us.

We decided that the greatest chance of getting the dinghy to hold air would be to put a patch on the inside of the tube first and, when this stage was complete, to put on external patches. The challenge was how to insert a patch (covered with sticky glue) without it adhering to every surface it touched — while still trying to position it correctly. By trial and error we eventually settled on the following technique.

Size of patch

We found that, regardless of the shape of the puncture, a circular patch at least 2” larger in diameter than the slit gave a big enough area to cover the hole. From a spare sheet of Hypalon or PVC (depending on your dinghy material), cut out two patches of the necessary size. Roughen the backs of these patches (so the glue adheres) and clean with some acetone or isopropyl alcohol.

Use some coarse sandpaper (80-grit) wrapped around your index finger to roughen the inside surface of the tube in a circle the size of your patch and clean with acetone or isopropyl alcohol. If necessary, enlarge the hole to enable you to reach inside. Also roughen the outside of the tube ready for the external patch.

Apply a first coat of the appropriate glue to the back of the internal patch. Semi-inflate the tube (as best you can) and, using a gloved finger or popsicle stick, also apply a first coat of glue to an area the size of the patch on the inside of the tube. (It is best to use two-part glue and follow the manufacturer’s instructions carefully. This normally includes applying a second coat of glue once the first coat has dried (about 20 minutes) and just before sticking the two surfaces together.)

We solved the problem of positioning the patch on the inside of the hole by using the natural “springiness” of a sheet of acetate (we used overhead transparency film). Cut out two pieces of acetate a bit larger than the patches. Thread a needle with some cotton and tie a knot at the end. Insert the needle and thread first through the centre of the two pieces of acetate and then through the internal patch, leaving the glue side out.

Second coat

Apply the second coat of glue to the inside of the tube and also to the internal patch and wait until it is touch dry (about five minutes). Roll the patch and the acetates into a slim tube with the glued patch outermost. Carefully insert into the hole far enough so that they can be suspended inside the tube using the needle and thread. Carefully position the thread so it is in the middle of the hole (thereby centrally locating the patch) and pull up on the thread until the patch is in contact with the tube. Deflate the tube (if it hasn’t already) and press the tube firmly onto the patch on a flat surface.

After about 20 minutes, inflate the dinghy to provide pressure on the internal patch. When the last hole has been repaired in this way, the tube should now hold air. Cut the thread close to the surface and apply the external patch in the normal manner.

Using this method we patched all 14 stab wounds and re-attached the tube to the transom; only one hole developed a slow leak. We have now repaired that hole again and the dinghy has a new name — Spot!