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Rehabbing an inflatable

Apr 5, 2011

Simple steps to revitalizing an older inflatable
dinghy

Inflatable boats come in all sorts of configurations and sizes. All are pretty stable platforms, are highly maneuverable; and usually cost far less than a hard-hulled vessel able to perform the same tasks.

Remember: these boats are really air-filled, rubber- (or PVC-) coated, fabric balloons. And like all such fabrics, by being extremely flexible, and exposed to UV radiation, their life expectancy is limited. Because of their buoyancy, and their small displacement, inflatables have a huge cargo-carrying capacity. In addition, because their air is held at very low pressure (mostly 2.5 to 3 psi versus the 30 to 50 psi of a motor vehicle tire); they are inherently safe, for they lose air very slowly when punctured. Also, except for the smallest, most have from two to four flotation chambers.

Take my battered, 31-year-old Achilles dink. Like all its brethren, it has suffered chemical degradation thanks to sunlight. Then came the mechanical impact of submerged rocks, or from rubbing against crustacean shells on pilings. Further, after being dragged to a launch site, add in sand abrasion. The final blow — more often than not while in storage — were hungry rodents chewing a hole.

Inflatables are made with a flexible sandwich consisting of a nylon or polyester outer coating over a very durable fabric mesh — and placed on the mesh’s other side, an impermeable inner bladder made of PVC. The priciest dinghies have these inner and outer coatings made of Hypalon — a synthetic rubber which at present, is claimed as the most effective retardant to UV damage, and its attendant short life-expectancy and air loss. However, some PVC coatings and formulations seem to work just as well. Unfortunately, repair procedures and materials for each type can be unique, so you must first identify the coating used on your boat. If in doubt, a short call to your manufacturer should answer the question.

Check inflation valves first
Should air leakage be the problem, it would be a good idea to first check whether your inflation valves are at fault. The valves are the easiest, cheapest thing to replace. To test them, simply unscrew each valve-body, place it backwards in your mouth, and with its cap pushed aside, blow hard in the opposite direction used when inflating — while making sure your lips and teeth are in contact only with the valve’s rigid structure, and nothing else. Should you succeed in pushing air this wrong way, that valve must be replaced: and if you are very lucky, that will be the end of the leak. If so, get two — plus an inflatable air-pressure tester, if you do not already have one. (Automobile tire gauges are meant for high-pressure loads only, as they do not even begin to register below 20 pounds and are totally useless here). With two valves, you will have a spare one to use, lend, or trade as the occasion might arise. Now, with a good valve in place you are now ready to determine the size and complexity of the inflatable segment of your rehab project.

If there are cuts and holes to span, now is the time to assemble the materials for that patching task. Here you will find several suppliers — most of which provide a kit. This usually includes a set of instructions; a sheet of abrasive paper to give ‘teeth’ to the damaged surface so the mending patch will adhere firmly to it; a bonding agent; and a 6- by 12-inch sheet of rubber. Some will also include a half-inch to one-inch roller to press out all air between patch and hull, (if not, you can get a cheap one at any hardware store); plus sometimes a tube of cleaning fluid. You will also need a pair of scissors to cut the patch, plus plastic gloves and a mask. Remember, the chemicals you will be dealing with are toxic and volatile, so good ventilation is essential — and so is inhalation protection — hence the need for both gloves and mask.

A single materials source
My preference has always been to work with a single materials source whenever possible, for their interaction is then a known factor. In my case I chose Inland Marine for the patching kit. It applies to both: Hypalon and PVC — even though they recommend a different cleaning fluid for each — both available at hardware stores. Once you have decided which process fits your boat, cross out the other, so you cannot mix them up. Then make a checkout list, for the process will take several days.

Bear in mind that for all the chemical steps needed to rejuvenate your boat, the most crucial (and the one most likely to be rushed), is the prepping process — the foundation to all the bonding work you will be performing. So, unless you enjoy building sand castles and waiting for the incoming tide to wreck them, check and double check that each step called for in the manufacturer directions has been done: no corners cut, no steps skipped. If you are like me and are impatient to get the job underway and done, you are apt to misread, or willfully avoid or overlook some instruction. That will almost guarantee you will later be backtracking, and what earlier had been a simple matter, is apt to be a major mess.

Big holes first
Start with the big holes, making sure your patch will extend generously over all sides of each. If the hole or tear is bigger than say 2.5 inches, and if it’s a ragged one, it is most likely the work of Mr. or Mrs. Rat. After you have trimmed the hole’s edges into one continuous circular or oblong shape, consider patching both sides of it. If the patch must also bridge a seam, be extra careful for that could be a problem spot. Be generous with your bonding material there. First mark and overlap the patch up to a healthy one-inch all around the hole to ensure a good bond, and cut your patch (or patches) accordingly.

That done, proceed with the bonding process as the instructions direct. In my case this included a curing time — up to two days at ambient 75 to 85° F. If that is not available, a heating pad or light bulb can help do that job well. Check out the proper heat-source distance with a thermometer. Your kit may have other specs — follow them carefully. Incidentally, if you have problems securing a parting rub-strake or the bases for D-rings; use the above procedure to secure them as well.

So now you have carefully followed all directions and have successfully mended all holes and cuts. But wait, you won’t know that for sure until after the curing process has been completed. And then, to be doubly sure, wait an extra day. That done, it’s time to inflate your boat. If you have your air gauge, pump each chamber up to a taut, but not stressed condition. Take a reading, and remember it. Now brush soapy water over each of the patched areas you worked on, and around the valves as well. Check all chambers. If any are still deflating, this means pinholes; which will need to be internally repaired after you are thoroughly satisfied your patched surfaces are not leaking.

An internal sealant
I used Inland Marine’s sealant. It comes in a quart container, and claims it’s enough to treat an entire 12-foot boat. So if you have a three-chambered dink, one third of the material should go into each. Before you apply it though, make sure there is someone around to help you tumble the boat. Make sure they will be available for the next three or four hours, too, the action must be repeated every half hour to properly distribute the sealant over all the internal surfaces. Once you and your crew are set, remove the valve, and insert the proper amount in accordance with the manufacturer’s directions. That done, the valve must be speedily reinstalled for the sealant sets quickly once it is in contact with air). Now re-inflate the boat to just below taut. Now you are ready to roll the dinghy sideways, and end over end, too. Don’t forget to keep enough beer or other essential fluids at hand to keep the tumbling crew happy and fit throughout the whole process.

You might also see abraded areas, areas that while not yet leaking, can make the boat look shabby. A topcoat will provide them with a protective and cosmetic film. I used MDR’s gray product, a quart of it is enough to lay one coat on most boats. It is also available in white, red, yellow, blue and black. It requires the use of a dinghy cleaner, I used MDR’s own Amazon — and followed their directions to the letter.

Holes on the boat’s flooring or sole can be easily detected and treated the same way as the hull. Sizable ones, if any, should get a patch on both sides. And if you go into salt water, or areas heavy with marine life, you might want to add a “designed for inflatables” copper-based bottom paint to the outer side. For an 8- to 11-foot dinghy, one quart should be enough.

—Alan Saunders is a writer and sailor based in Hawaii.

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