Refurbishing the Inflatable Dinghy

Inflatable tenders have become the family car for many cruisers. They haul groceries, take us to snorkeling spots, shuttle guests, haul out second anchors, and even tow the mothership if need be.  And yet, if they receive any attention at all, it’s limited to the engine and why it isn’t starting on the first pull. The body is ignored. Eventually the rest of her is going to need some attention, better sooner than later.

PATCHES

If she’s been losing pressure, give her a good scrubbing with TSP to remove all of the grime, and then slather a solution of hand dishwashing liquid all over and look for bubbles. Simple punctures, thin spots from chafing against the davits, and even small tears are easily patched. Only a little more complicated than patching a bicycle inner tube, just follow the instructions in the kit, remembering that PVC and Hypalon require different adhesives and materials. (Don’t try contact cement—it looks the same but will not hold.)The result should be permanent. If the dinghy has been painted, lacquer thinner removes the paint in a thrice without damage to the tubes (minimize contact time).

Patches over pinholes must be at least 2 inches in diameter, and patches over tears must extend beyond the tear by 2 inches in all directions and have round corners. If the patch intersects a corner seam, the best answer may be a tombstone-shaped patch, so long as the tear is at least 1.5 inches from the seam.

If the patch must cross a seam, apply the glue liberally in two coats and give special attention to rubbing the patch into the seam. Allow the glue to dry for at least 24 hours; if the tube is pressurized before the glue is set, the air will gradually separate the patch.

Both are over thin spots that seeped air, the result of the PO not properly securing the davit—swinging kills. Be very careful about the hard grab of Hypalon cement—we inadvertently slightly mislocated the right hand patch slightly outside the prepared area. A shake of the hand and it can’t be moved.

CHAFE PROTECTION

It would be nice if dinghies came with factory wear patches, like every well-made genoa comes with wear patches for the spreaders and bow rails, and a full-batten main has wear strips for the shrouds. But alas, the inflatable maker can’t know where the davits will rub or how you will use the boat. In my case, the lifting bridle for the bow rubs on the inside of the tubes. My practice has been a two-layer wear patch, so that I can renew the outside layer while I still have a layer of protection. A single layer is suitable most places. The intersection of the floor sheet and the transom is another wear area; a length of vinyl stair nosing can be glued on the outside, providing rugged protection—flexible polyurethane caulks such as Sika 295 or Locktite PL S40 work well. Polyurethane also works well for reattaching sun-stiffened PVC rubrails and handles, since it fills gaps better than the patch cement.

VALVES

A common source of slow leaks is a bad valve. Often horribly sunburned on the outside, the critical parts on the inside remain pristine, completely protected from UV. Most often, a good cleaning is all they need. Fortunately, they are dead simple to service or replace. Here’s how:

• Deflate the tender.
• Grab the inside portion of the valve by squeezing the deflated tube around it. Turn the top counterclockwise using either a valve-specific tool or a large pair of channel locks (gently). They are entirely plastic, and as a result, I have never come across one that has seized.
• Remove the top half and give it a good scrubbing with a tooth brush. Lube the sealing surfaces and the outside O-ring very lightly with synthetic or silicon grease.
• There is probably no need to remove the inside half—it just a threaded holder, never sees sun, and will probably last 50 years. They can also be tricky to force through old fabric (might tear).
• Give the top surface of the inflatable fabric a good scrubbing.
• Reinstall by reversing the process.

Give the plug a good scrubbing. Remove the gasket and get both sides. If the gasket appears crusty, it’s probably just an accumulation of salt and algae. Replace the keeper string with whipping twine. You can safely lubricate a valve in place with a few drops of glycerin.

Replacement valves are $15-$20. If the brand is not obvious, measure the hole in the fabric and send a picture to your friendly service rep at Defender Marine. Many are interchangeable. If the fabric around the hole is torn, sand and install a doughnut-shaped patch four inches larger in diameter than the original hole and reinstall the valve, remembering to insert the inside portion of the valve before you add the patch.

THE SUN

Hypalon will last a decade or more in the tropics, and twice as long in the temperate latitudes, where the sun angle is lower. PVC wilts much sooner; it seems such a bargain at first, but may only last a third as long.

The PVC handles and oarlocks found on many Hypalon dinghies bear obvious witness to the vulnerability of PVC; before the dinghy has reached its prime, thick, beefy fittings begin to fail. Sunbrella covers are one option, providing both chafe and UV protection, but expensive and often leaving critical areas naked. Storing out of the sun helps, but the hassle of inflating and assembling soon ends that.  Another option is paint, not for vanity sake, but rather as durable sunscreen.

We’ve used MDR/Amazon inflatable boat paint a number of times with good success. It is no more difficult to apply than latex house paint and lasts  5 to 8 years before recoating  is required. Scrub the boat well with an effective cleaner, such as TSP, and rinse well. The paint goes on with a brush, and we find we only use about one pint for a 9.5-foot inflatable, skipping the bottom and floor, which rarely see the sun depending on how you stow your inflatable on board.

It dries quickly, but like all latex paints, it should be allowed a full week to cure in hot weather before folding. Chose white or very light grey; dark gray looks smart, but it is hot to sit on and the heat affects inflation pressure, potentially leading to bursting.

DETAILS

Applying numbers. This may sound slapdash, and the catalogs are full of “neat” boards for hanging numbers. But applying registration numbers with a Sharpie and a stencil  wins in terms of sheer practicality; the numbers will never chip or peel, and they are easily retraced every three years when they begin to fade. Registration stickers will eventually loosen, but not until they are expired anyway.

Transoms. A plywood transom is often the Achilles heel of the inflatable. So long as it stays dry, they last seemingly forever, but if inner laminates get wet they don’t last long and are terribly expensive to repair.

Thus, be obsessive in keeping this properly sealed. If there is a sacrificial motor mount on the outside or inside, remove the engine and paint/seal as needed. Replace the pads when needed, sealing carefully.

Wooden Floors. They rot fast. You can try to keep them painted, but if the dinghy lives on davits, even with the drain open and the boat tipped, one corner will be wet most of the time. The solution? Replace only the stern section every 5 to 8 years (typically about $60-$100). Alternatively, these can sometimes be fabricated by the DIY sailor, matching the hardware, smoothing and radiusing the corners, and padding with closed-cell pipe insulation as needed.  Although it seems simple, do NOT make a one-piece plywood floor. Unless the boat was designed for that, the rocker will be wrong, the boat won’t flex as intended, and the seams will tear within weeks. We know of several people who tried this, and they were much worse off.

Tweaks. Sailors just can’t help themselves when it comes to upgrades.

• Cleats for Towing. Before attaching anything to the transom, remember that a rotten transom is generally fatal. Seal well. A pair of PVC pipes attached inside the transom, something like rod holders, function as multi-purpose strong points.

  

  In addition to holding fishing poles, paddles, and the tiller extension, they also serve as strong cleats. Simply tie a loop in the rope, drop it over the pipe, and insert a pole to keep it. The resulting attachment point that exerts practically no leverage on the fastenings and can be used to tow multiple kayaks or even a larger boat. We’ve used this system to heel a large boat that was grounded, helping them off a bar. With a sturdy pole inserted, they can serve as a handhold for passengers and a boarding aid.

• Milk Crate Under Seat. It’s asking a lot of those straps that  hold a seat that people will sit, bounce, and step on. To provide additional support, and storage to boot, hunt around for an industrial milk crate with a steel bar reinforcing the top edge, not one of those lightweight dorm models. Wood strips can be added to the bottom to bridge seams in the floor and adjust the height.
• Engine. Our 3.5 hp Merc 2-stoke will seem anemic in size to many, but I like her reliability and super light weight. She’s happy as long as I feed her gasoline laced with Biobor EB to prevent aluminum carb corrosion and the resulting clogging. Be sure to keep the vent closed when not driving to keep the water out. Just a single squall with the vent open can ruin a tank of gas. I also added a lawn-mower type in-line gasoline filter just before the carburetor, since like most small engines with integral tanks, the engine came with only a crude strainer in the tank—an easy $5 upgrade. Recommended for any engine lacking a replaceable filter.

CONCLUSIONS

As our Hypalon tender enters its third decade, we can’t help but be amazed how well the fabric handles the sun and the bumps that come with cruising. She has a few patches, we’ve painted her twice, and the valves have been removed for a good cleaning. The floor has been rebuilt several times and finally replaced.  And she is like new again, like a broom that has seen three new handles and two new heads.age. Add protective patches everyplace the tender bears on the boat when carried.