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History of Inflatable Boats

According to the Guiness Book of Motorboating, the history of the inflatable goes back as far as 880 BC, when the Assyrian king Ashurnasirpal II ordered troops to cross a river using greased animal skins, which they inflated continuously to keep the vessels afloat. In ancient China, during the Sung and Ming dynasties, inflated, airtight skins were used for crossing rivers.

It was 1839, however, that the first inflatable pontoons were tested by the Duke of Wellington. In 1840, the Englishman Thomas Hancock designed inflatable craft and described this work in "The Origin and Progress of India Rubber Manufacture in England" published a few years later. In 1844, a Lieutenant Halkett designed a round-shaped inflatable bloat which was used in several Arctic expeditions. The Frenchman Clement Ader devised a floating vessel too. Indeed, many other pioneers invented craft that foreshadowed "inflatables". In 1913, the German Albert Meyer came up with a fairly novel design. By 1920, his company, A. Meyer Bau Pneum. Boote, was marketing his "pneumatic" boats, of which nine were already in use by the German Army.

In France and Great Britain, Zodiac and RFD claim paternity of the first modern inflatable boat. In 1919, RFD's founder Reginald Foster Dagnall tested an inflatable on Lake Wisely in England, and went on to improve its design in the 1930s. This boat was the ancestor of the one-person inflatable liferaft. In France, Pierre Debroutelle came up with a prototype for an inflatable boat in 1934.

The first boat of its kind to be certified by the French Navy, Zodiac's model probably sparked the development of the civil and military inflatable boat industry. Unlike its counterparts, the boat improved by Pierre Debroutelle in 1937 was actually designed in a U-shape, with the two lateral buoyancy chambers connected by a wooden transom patented on August 10, 1943. This version was the direct predecessor of today's inflatable sports and pleasure boats.

Since then many new manufacturers, new models and new designs have hit the market. Inflatable boat are no longer a little dinghy on the back of a large pleasure yacht, but can range up to 45 ft in length and longer. "Rigid" hulls of fiberglass or aluminum have evolved from the original fabric floors, luxury components and even cabins now grace the decks of many inflatable boats. Contrary to the name, inflatable boat, on some inflatable boats of today the only thing inflatable is the collar around the perimeter gunwales of the deck however, the inflatable boat lives on and becomes more popular year after year.

(Information courtesy of "A Century of Air and Water" 1896-1996, a publication printed by Zodiac International on their 100th anniversary)

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Uses of Inflatable Boats

Initially, inflatable boats were developed for use in the navy for transporting torpedoes and other cargo as well as other applications. Over time, recreational applications evolved for the smaller boats including pleasure, tender and fishing. When the stability, flotation and seaworthiness of inflatable boats became more known, lifesaving and rescue agencies around the world began using them as tenders on their larger vessels. Today, rescue and military agencies around the world use inflatable boats, particularly RIBs, for many applications inshore and offshore. Some of the many applications of inflatable boats today include:

....and many other applications.

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Types of Inflatable Boats

Yacht Tenders
This category is ideal for first-time boat buyers, or for anyone seeking a practical all-purpose boat offering maximum safety and stability at an affordable price. The size of boats in this category range from about 6 feet up to 20 feet. There are four distinctly different hull (or bottom) configurations available in a modern yacht tender inflatable:

 The floors of these inflatables consist of a layer of fabric and slats (usually wood) running across the beam. They're usually painted or stained and are about 4 inches in width. The slatted floor system is generally found in inflatables from about 6 to 8 feet in length only, where there is no need for performance. Consequently, these inflatables don't tow, motor or row as well as inflatables with an inflatable keel and v-hull.

V-hull (wood or inflatable keel)
This consists of a separate longitudinal inflation tube or wood keel located beneath the floorboards. Once inflated. it provides a moderate V-keel at the bow of the boats by pushing the fabric floor down and away from the floorboards. Handling and performance is greatly improved as the keel cuts through the water cleanly. An added benefit is the extra buoyancy and flotation it provides.

High-performance hulls
Here is where you go from conventional inflatables to inflatables offering high speed coupled with excellent handling. However, this added performance can often create a false sense of security and may lead to boating accidents. These boats are recommended for more experienced boaters. An example of a performance hull would be Zodiac's Futura model. The patented Futura hull has smaller "speed tubes" attached below the regular collar. Upon reaching plane the boat lifts up onto these speed tubes, trapping air underneath and exerting positive lift (hydrodynamic lift), leaving the boat riding on these two "speed tubes" like a racing catamaran.

Rigid-hulled inflatable boats (RIB's)
As their name suggests, these boats feature a fiberglass rigid hull mated to an inflatable collar. This allows a conventional deep V-hull shape at the bow, flattening out to common planing sections aft. The concept marries the famous buoyancy and stability of an inflatable boat with the excellent handling characteristics of a conventional fiberglass hull. The larger boats in this range offer a wide range of console configurations, seating and other features such as built-in storage lockers, and many other features typically found on larger fiberglass vessels.

The benefits of the RIB are quickly seen in increased performance and handling, coupled with versatility, stability and passenger comfort. The smaller rigid-hulled inflatables make excellent yacht tenders for larger yachts, while the larger RIBs make perfect watersports or fishing boats, particularly because of their flotation, stability and safety. Many rescue and military agencies have recognized the seaworthiness, safety and stability of RIBs and use them in many applications. Also, many of the RIBs offer removable collars making storage, maintenance and repairs much easier and convenient.

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Design and Construction Features

Load Carrying Capacity
A key feature about all inflatables is their incredible stability. Conventional dinghies and small sport boats rock almost uncontrollably whenever anyone moves about. Inflatables, with their buoyancy tubes, sit flat in the water and are almost impossible to flip over. This offers a feeling of security to even the most nervous boaters and allows swimmers or divers to slide back on board without upsetting the boat.
More buoyancy means bigger load-carrying capacity. Inflatable boats are designed with built-in buoyancy. The inflatable collar, or tubeset, is the key that allows inflatable boats to carry very heavy payloads in a safe and stable manner. An added benefit is that they are virtually unsinkable, and can generally operate even with one or more chambers of the collar deflated.

High performance
Most of today's modern inflatables easily match conventional runabouts for speed and handling, while some of the more sophisticated rigid-hulled inflatables are clearly superior to ordinary fiberglass or aluminum boats. For instance, the Virage range of sports boats features Zodiac's patented Futura speed tubes to produce amazing lift and stability. Because the Futura hull merely kisses the water, it creates less drag and thus requires less power to reach incredible speeds while performing with absolute safety. The big rigid-hulled inflatable superboats are equally impressive. With deep V-keels up forward and flat planing sections aft they can produce an astonishingly comfortable ride in tough offshore conditions, yet maneuver with ease in the tightest dock or harbor.

Non-marking features
Inflatable boats are the ideal yacht tender because of all their basic advantages including: lightness, stability and buoyancy. Unlike regular dinghies, they're easy to lift on board. With special rubstrake glued or thermobonded to their sides, inflatables won't damage or mark your yacht's hull or deck. Purchasing an inflatable tender almost guarantees the elimination of scuff marks and scratches on your yacht forever.

Stowability
Inflatable tenders are much easier to store than conventional dinghies. When deflated and folded into its carry bag a typical 8 foot inflatable measures about 3 feet x 2 feet and weighs about 80 lbs. At this size, you can see that an inflatable tender is easily stowed in a locker on board, below decks or in a closet or shed at home. They're also very convenient to take on picnics or on vacation, even in a small car.

Collar (buoyancy tube) design
A unique feature incorporated into many rigid-hull inflatables is the removable collar. The collar is securely attached to the fiberglass hull using a tongue-and-grove method and can be easily slid off whenever necessary. This system allows for convenient storage, maintenance and repairs.

Lightweight air-floors
Some of the more advanced inflatables, like Zodiac's Fastroller, feature a special High-Pressure inflatable air floor. Made of two layers of fabric, connected by thousands of tiny "drop stitches", this floor can be inflated to a high pressure, creating a floor with rigidity equal to sheet of plywood a fraction of the weight. Best of all, they can be completely deflated and stowed in only minutes without removing any parts. This high pressure air floor is softer on knees and backsides too.

Transoms
Given the size, weight and power of outboard engines today, the transoms of inflatable boats must be strong enough to withstand enormous vibration and stress. Many inflatables use multi-layer wood transoms that are glued or "thermobonded" to the collars. The result is a high degree of structural strength that reliably absorbs stresses exerted by outboards.

 

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Types of Fabric

A major component of an inflatable is obviously the fabric. Fabric technology has evolved greatly over the last 20 to 30 years, and now includes plastomers, polyurethanes and other fabrics, which can sometimes be stronger, lighter, thinner and less expensive to assemble than the original rubber fabrics. Of course it costs a great deal of money to develop new fabrics or even to switch manufacturing processes to use them. Many manufacturers, big and small, don't have the will or the resources to do this, and that's why they generally hide that fact by resorting to condemning new technological advances in fabrics.

For instance, Zodiac's fabrics have always been on the leading edge of technology and their willingness to research and experiment has led to some innovative new fabrics. These new fabrics are developed to be the best for their intended use. Fabrics used for a small tender don't need to be the same as those for a large RIB, because the intended use is not the same. Some manufacturers do not have the means or know-how to employ different fabrics, so they just use one. In these cases the consumer, may end up paying too much or getting too little.

Most fabrics consist of a strong, close-weave mesh of polyester or nylon material which is sandwiched between 2 coatings to provide extreme flexibility, superior air and water tightness, as well as resistance to abrasion and the sun's UV rays. Zodiac uses a polyurethane fabric called "Strongan" and assembles their inflatable boats by thermobonding the fabric.

 

Fabric Differences in Inflatable Boats

The basic difference between boat manufacturer's fabrics is the chemical composition of the materials used.

In supported fabric boats (those with threads in the material), the fabric strength is measured by the weight of the thread used. Denier or Decitex(metric) is the unit of measure, not a type of fabric.

1000 Denier = 1100 Decitex

The type of thread varies from Dacron to Nylon as does the tightness of the weave. Many heavy duty backpacks are listed at being made of 1000 denier thread. Most foul weather gear is 220 or 440 denier. Zodiac boats are made of 1000 denier and up fabric (the HD's are as high as 1800). Some other companies vary the weight of the fabric with the weight of the boat. Some "light" duty boats are 200 denier.

The tightness of the weave is another measure. You may have a 9x9 weave (threads/square centimeter) or a 3x3. The weight of the thread is important when considering weave density. You can put many pieces of thread in a square centimeter, but a 2x2 weave of 1/8" line will
be stronger. Density must make sense with fabric weight.

The coatings and the process of applying the coatings separate the products as well. Zodiac uses a synthetic material which is continually evolving. Using long-chain plastomers ("polymers"), many compounds are formed. Nylon and Polyester are 2 examples. The alternative is to use natural rubber compounds. These are commonly Hypalon and Neoprene in the boating industry.

Synthetic materials allow compounds to be formulated for the specific application. The external coating can be designed for UV and abrasion resistance, while the inner coating can be focused on air integrity. With natural compounds, this becomes more difficult.

Natural fabrics have to be glued to assemble the boat. Zodiac uses a thermo-bonding technique, similar to electronic welding. The welds become stronger than the fabric itself. The welding process also allows a reduction in labor costs and more precise production as it is all automated.

From a reality point of view, both are excellent materials. Each has its weaknesses. The most noticeable difference is that the natural rubber compounds will chalk in the sun. This means you' might get a red butt when going ashore in your dress whites.

Neither fabric should be treated with a petroleum or silicone based product. An example of such a product would be ArmorAll®. The product won't hurt the fabric, but it will prevent glue from adhering to the it. You boat will begin to come apart at the seams. There is very little that can be done once this happens. Repairs are difficult at best.

For all inflatables, we highly recommend 303 Protectant, available at automotive stores and the mass merchandisers. It is a water based polymer that inhibits the destructive forces of Ultra Violet rays and it seals the boat against the penetration of dirt. We found that 303 made our boats easier to clean at boat shows and in the display room. 303 can be used on fiberglass, plastic, dash boards, tires, etc. A major benefit is that is does not trap the UV rays inside the coating. This prevents heat build-up, which can be a problem with some other silicone based products. See the link below to order 303.
 

Heavy Duty Fabrics
Some inflatable boats are still made from a rubber-based fabric called Hypalon. While this is still a very good material, its major downfall is that it can only be joined by gluing, done manually. Problems including poor bonds, delamination of seams or fabric can still affect these glued fabrics. Today, many inflatables are manufactured from polyurethane fabrics, although larger inflatables (particularly RIBs used for rescue or military purposes) use hypalon because thicker hypalon fabrics are still considered to be stronger and more durable than polyurethane. There are some hypalon fabrics that are "2-ply" or a double unit made up of hypalon/weave/hypalon/weave/hypalon and are used for extreme situations including bumper padding, bow skirts, anti-chafe patches and similar applications.

Seams
Apart from its superior toughness and durability, Zodiac's Strongan fabric allows the use of Zodiac's computerized machine-welding process known as "thermobonding", the welding of fabric using hot air. Two sealing strips are thermally bonded to the butted fabric seams in a continuous electrothermal process. A highly airtight seal is created when the narrow inner strip literally melts into the collar material. The wider exterior strip functions as a overlapping structural connection and a sealer against water penetration. Thermobonding creates seams that are typically stronger than the fabric itself and produces a better seam than any hand-gluing method.

Copyright 2002 Paragon Communications / All Rights Reserved