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How to Decide on the Right RIB - Sail Magazine

How to Decide on the Right RIB

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A rugged, reliable dinghy

A rugged, reliable dinghy is an essential adjunct to the cruising lifestyle. Photo by Tom Hale

A hard dinghy serves well to row out to your mooring and set off on a day sail. For weekending and vacation cruising you will find a lightweight inflatable with a small outboard serves you better and allows you to go further. As your cruising range extends, the demands on your dinghy change. By the time, you get ready for long term cruising, you will appreciate all that a rigid inflatable dinghy has to offer.

My wife, Cristina, and I were forced to reexamine our dinghy needs on a trip through New England’s Buzzards Bay on our 31ft C&C. Our 9ft air-floor inflatable with a 2hp outboard was so light we could easily stow it on the foredeck, and it rolled into a small package when not in use. It moved the crew back and forth to shore for many years.

Even when we moved up to a 38ft boat, the little dinghy happily skipped along behind us all over New England, until one day when we encountered a heavy squall. The dinghy flipped in the wind and waves and we had to wait until the squall passed before we were able to get it up on deck, with the motor ruined and one tube punctured. It was time to take a hard look at our options. Our cruising style had changed with our larger boat. No longer were we day sailing and weekending—we were now able to cruise for weeks or months at a time.

As full-time cruisers, we knew that our dinghy would be in near daily use. Our beagle, Aurora, was pretty well pad-trained, but she deserved a run on the beach twice a day. There are creeks, gutters and hidden coves to explore, white sandy beaches to shell and reefs to snorkel. It would be nice to have the space and power be able to carry a tank of propane, blocks of ice and a week’s worth of provisions out to the boat. We plan to spend close to six months a year in the tropics. We will beach on sand and shell, rock and coral. Clearly, some sort of a hard-bottom tender was in order. 

After talking to other cruisers and several inflatable boat dealer experts, we understood that the choice would not be simple. Experienced cruisers advised us to select the largest dinghy with the largest outboard that we could handle and bring aboard. The size and shape of our boat would affect our storage choices and our storage choices would affect the size and weight of the dinghy. The decision tree is a circle.

The decision to go to a RIB was a simple one. The hard, slightly V’d bottom planes easier, runs faster and turns better than an air floor. The RIB tows better and is far less likely to flip when under tow. The bottom is better suited for beaching without worrying about sharp objects. With a RIB, it is easier to clean the sand out of the boat.This was a constant issue on our air floor, where we had to wash under the floor to get the sand out after each cruise. Talking to cruisers, we found the consensus is to go with a boat between 9ft and 11ft with the biggest outboard you can handle.

comparison

Note the differences in hull shape between the West Marine Compact 310, with its folding transom, and the heavier RIB 310 (right)

HULL DESIGN

There are two options for the hull interior layout. The boat is either a single-skin RIB, where you walk on the inside of the hull bottom or a double-skin RIB where you walk on a flat floor inside the boat. The single-skin types are by far the lightest RIBs available. These boats will not have a storage locker in the bow. They also accumulate bilge water in the V bottom; your feet and cargo are almost always wet. While this is not perhaps a problem in the islands, a lot of our cruising would be in temperate climes.

Folding RIBs are a variation on the single-skin hull design. The transoms on these boats fold over for storage. When deflated, these boats are about the size of a stand-up paddleboard. They are the lightest of the RIBs, but they are about 20 percent heavier than an air deck inflatable. For weekend cruising this can be a good choice for a RIB dinghy. They tow easily, run well, and when faced with the prospect of a rough passage, are light enough to put up on deck. Many cruisers also like them because they store easily in a dinghy rack ashore and thus are out of your way for day sailing. The dinghy is only brought out when you are planning to overnight at anchor.

Double skin RIBs have a flat interior floor and a sump or bilge area to accumulate spray and water. These boats carry a weight penalty, being 10-20 percent heavier than the equivalent single skin RIB. We were leaning towards a flat floor design with a bow locker, even with the extra weight penalty.

ALUMINUM OR FIBERGLASS?

RIB hulls are made of one of three materials. One builder uses injection-molded polypropylene, a tough and forgiving material, for the hulls of certain models. The rest of the market is dominated by fiberglass or aluminum RIBs. Talking to other cruisers, we learned that aluminum dinghies are lighter than their comparable fiberglass hulls. They are, however, surprisingly noisy and some cruisers are unhappy with the performance, finding them too light to handle rough water. Reports that some aluminum dinghies suffered glue failure at the tube bond to the hull also concerned us. Some owners had problems with water getting between paint and the aluminum surface. The glue bond to the paint was tenacious, but the paint itself was not adhering well to the aluminum. This issue seemed to be eliminated in RIBs with white powder-coated hulls.

In the cruising community, the abrasion resistance of aluminum drives the choice over fiberglass. But be aware that the gauge (thickness) of the aluminum is not the same for all builders. Of the boats in use, some of the lightest hulls we saw flexed in the flat areas of the bottom where the scantlings are too light. Aluminum dinghies are tough but also carry a price premium. No one we spoke to with a fiberglass hull had ever had a rock hole their dinghy.

HYPALON OR PVC?

RIB tubes are built of PVC or Hypalon/Neoprene. As a buyer, you must be cautious, because within these two fabric lines there are significant variations in the formulation, thickness, and underlying cloth. From our attempt to understand the fabric selection it became clear that only an experienced inflatable-boat dealer with boat repair experience could effectively guide us through the information. Some high grades and compounds of PVC are stronger and longer-lasting than some lower grades of Hypalon.

Hypalon has a strong and loyal following in the cruising community. It is generally more resistant to UV radiation and to fuel, and it is a heavier and tougher fabric. On the other hand, it must be constructed with hand-glued seams. These two factors make a Hypalon boat a little heavier (about 5 pounds) and a lot more expensive. The hand-glued seams of a Hypalon boat are not perfectly airtight either: it will be necessary to top off the air weekly. PVC tubes, on the other hand, may not be as resistant to UV, but the seams are welded and they do not leak. For seasonal cruisers whose boats are stored in the winter, PVC may be the best choice in boat fabric.

Many cruisers fit their boats with chaps—fitted canvas tube covers that provide protection from UV light and from abrasion, cuts and scrapes. For long-term cruisers who use their boats every day and spend much of the year in the tropics, chaps provide valuable protection for the tubes. We were planning to add chaps to our next dinghy regardless of the tube fabric choice, and the exceptional air-holding capability of PVC at a lighter weight with significantly lower cost (25 to 30 percent cheaper than Hypalon) was attractive.

HORSEPOWER

Most cruisers are adamant their dinghy should be able to plane when fully loaded. This isn’t to say you will not find cruisers who are happy with 2, 3, or 6hp outboards. But we met no one who wished they had a smaller outboard. Some cruisers carry two outboards; the dinghy is such a critical piece of equipment that it’s prudent to have a backup gas or electric motor. Some carry a lightweight outboard for harbor duty where being on plane is not important and have a larger engine for the many times that they want to be able to cover greater distances on plane. We learned that an 8hp two-stroke or a 9.9hp four-stroke is about the minimum to plane most dinghies of this size range, but 15hp outboards are common on 10ft dinghies.

STOWING THE TENDER

The first RIB dinghy we looked at had a folding transom. In some respects, it was similar to the air floor dinghy we had used for so many years. It did not, however, meet our “dry feet” requirement and we had already shown that we could not be relied upon to hoist the dinghy to the safety of the foredeck when we were sailing. Hoisting a RIB with the halyard and storing it up on the deck makes sense when you’re making a long passage, but it’s not practical for day-to-day use. First, you take the motor off and put it away. Then you hoist the dinghy with a halyard, which requires two people. Then you lay it upside down on the deck and strap it in place. When you anchor in the evening, reverse the process. A davit system can be operated by one person in a fraction of the time, and the outboard can be left on the dinghy (so long as it is diagonally strapped for rough weather).

For our cruising, we needed a dinghy lift or davit system. RIBs are heavier than inflatable dinghies. The equipment to lift, store and deploy the RIB can be as big an expense as the dinghy and motor. We had learned the hard way that ease of retrieval would add years of life to our dinghy. A stern arch is a handy place to lift the dinghy, mount solar panels and mount antennas. More cruisers are installing them, but they come with a steep price. Dinghy davits do much of the same for a lot less cost. Since we have solar panels on the bimini top, we elected to go with stainless steel davits.

With the dinghy storage question now settled, we set about finding a dinghy to fit our other parameters. It was suggested by the inflatable boat dealer that we choose a dinghy about two feet shorter than the boat’s beam of 12ft 6in. The next detail of the decision process was the matter of weight. The 4:1 purchase ratio on the davits reminded us to pay close attention to the total weight of the dinghy and its motor.

As we worked through a variety of models from several manufacturers, we found the weights varied as much as 80 pounds and that the published boat weights were not always correct. We finally resorted to physically lifting the dinghies to get a truer sense of their weight.

Decisions, Decisions

We headed south last fall with a 10ft fiberglass rib with chaps covering PVC tubes and a 9.9 hp 4-stroke outboard. The dinghy was securely diagonally strapped to the new stainless steel stern davits. Over the winter we made a few changes to the dinghy equipment. We replaced the 6-gallon fuel tank with a pair of 3-gallon tanks so that the fuel is more frequently turned over and replaced. That and a good inline filter prevented us from having any fuel-related problems. We also found that a dinghy anchor is a simple solution to securing the dinghy for a walk on the beach, rather than carrying the boat up above the tide line. By the time we returned home the following spring the dinghy had traveled almost 5,000 miles. It had been used almost 200 days and had been deployed and retrieved a hundred times.

Dinghy Gear

The author’s RIB has been outfitted to suit his cruising style

Dinghy Gear

1. Mesh bag for twin painters

2. Lifejackets and registration stow in bag under the seat

3. Mesh bag for anchor line

4. Anchor

5. Fuel filter

6. Push pole for getting off the beach in cold water and for depth finder in opaque water

7. Dinghy lock cable— necessary south of Georgia

8. Stern lines: note all lines are different colors to help sort out the spaghetti in the bilge

9. Note small 3-gallon fuel tank. Fuel turns faster, stays fresher

Resources

AB Inflatables abinflatables.com

Achilles achillesboats.com

Avon Marine avonmarine.com

Brig brig-ribs.com

Defender Marine defender.com

F-RIB foldablerib.com

Highfield highfieldboats.com

Quicksilver quicksilver-boats.com

Walker Bay walkerbay.com

West Marine westmarine.com

Zodiac zodiac-nautic.com

April 2017

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