The Future is Unfolding

October-November 2001

This is an article from WaveLength Magazine, available in print in North America and globally on the web.
To download a pdf copy of the magazine click here: > DOWNLOAD

Elle Ralph Hoehn

Folding kayak technology began to develop over a hundred years ago. The concept of building boats which could be disassembled easily was born before the spread of the automobile. Boats had to be light, pack small, yet they had to be rugged and provide excellent performance on the water. And these requirements have been met in many different ways.

The Frame

The author playing in the new Triton "Lagoda"
round bilged folding sea kayak.

The way the frame is laid out and constructed affects how light the boat is and, more significantly, how small and easily it will pack and reassemble. Folding boat frame construction challenges have provoked an astonishing wealth of ingenious engineering, both in man-made materials and in wood.

Wood was the ideal frame material, although some folding canoes built in Chicago in the late 19th century had iron frame components. Ash wood quickly established itself as the best compromise of weight, resilience and strength in most applications. Wood is still the appropriate material to meet many folding boat design challenges,
especially when combined with modern adhesives and coatings.

Aesthetic considerations alone would be sufficient to guarantee wood a future even in new boat models. Klepper, Nautiraid, Pouch, Seavivor and Whalecraft uphold a strong tradition of construction in natural materials while ever exploring new methods and materials.

However, aluminium and various plastics have truly come into their own in the last 20 years or so. The main advantage of man-made materials is reduced weight, but the user also benefits from reduced boat prices, resulting from improved manufacturing efficiencies.

Feathercraft and Folbot have used both molded and sawn plastic transverse frame members, which are built with great, reproducible accuracy. Both firms use aluminium tubing for longitudinal frame members. Triton (of St. Petersburg, Russia) equips transverse frame members of bent aluminium tubing with special plastic fittings to join them rigidly to aluminium longitudinal frame members. The Sigma line of boats by Kayak Labs (regrettably inactive these days) introduced large diameter, relatively thin-walled aluminium tubes to achieve rigidity, great strength and ease of assembly without sacrificing low weight.

Longitudinal frame members of composite materials represent another innovation, overcoming concerns of oxidation and galvanic reactions between different metal alloys in folding boat frames. Watch for the introduction to the American market of the Japanese Fujita folding boats (www.foldingcraft.com). Developments with man-made materials are ever ongoing.

The Skin

The skin must be of the lightest possible weight, while neither contracting nor expanding as a result of changes in temperature and humidity. Today's skins have surpassed the mere function of "keeping the water out of the frame". According to traditional wisdom, frames must not rely on the skin for strength and stiffness. Modern fabrics and coating materials have made it possible to integrate the skin fully into folding boat engineering. In a balanced system, the skin reliably provides the tension that keeps the frame members in constant compression.

Decks were traditionally built of canvas (which, once the canvas is wetted, becomes nearly watertight due to the consequent swelling of the cotton fibers). While canvas is still in wide use for decks, folding boat manufacturers have been introducing a variety of man-made fabrics and waterproofing systems to deck construction. Reduced weight results, but also an almost complete elimination of rot and shrinkage problems, which once dogged natural fabrics.

The hull must provide sufficient abrasion resistance where it touches the longitudinal frame members (oyster shells on the outside, sand on the inside). It also has to be puncture-resistant (that rusty reinforcing bar sticking out of the muddy harbor bottom). Hulls were originally laminated of two or more layers of canvas, coated and interleaved with layers of natural rubber. Single layer polyester or nylon substrate fabrics have since taken over as much more durable and stronger hull materials. Manufacturers coat and impregnate them with synthetic rubber (Hypalon, for example), vinyl (PVC) or, more recently, polyurethanes. As well as being rot-proof, the newer skin materials are also almost completely unaffected by UV degradation and aging.

Commercially built folding boat skins have tended to be relatively heavy. In fact, manufacturers have little choice but to over-build to enable them to withstand inevitable abuse without complaint. Feathercraft has recently reduced skin weight through the introduction of an excellent, highly abrasion-resistant polyurethane
coating on a tough fabric substrate. Triton, in contrast, uses a relatively light, low-cost PVC coated skin, but applies narrow, tough PVC strips to reinforce specifically the run of the longitudinal frame members against external abrasion. The substrate fabric is puncture-resistant enough, when combined with its ability to flex between frame members, to safeguard a very tough yet light skin by this alternative approach. There's more ways than one to skin a boat!

Maintenance has been reduced to insignificance with the introduction of modern materials and methods. The challenge of producing at low cost is also being met by modern manufacturers. New folding boats are available in a price range of about $1,200 to $6,000 (US) depending on the different refinements required.

Is there anything left to improve? We can categorize the problems and directions of development in solving them in modern folding boats as follows:

Performance

Increasingly the expertise of marine engineers and naval architects is finding its way into the realm of folding boats. They reinterpret the existing body of knowledge of building big ships and other larger craft in its application to paddle craft, including skin-on-frameconstruction-even including the exploration of round-bilged hull shapes in contrast to the traditional chine hulls.

Modern designers are analyzing traditional hull shapes and degrees of flexibility which have evolved over centuries for hunting in an attempt to reach a better scientific understanding of the various design features and their intelligent application to new (folding) skin-on-frame concepts.

Ruggedness

Modern synthetic materials have dramatically increased the ruggedness of folding boats and will continue to do so. The ease of repair and maintenance of individual components is obvious. Combine these two features and you have the potential for great longevity, which translates into a worthwhile investment for the buyer.

Some manufacturers have discovered the trick of inserting strips of closed cell foam between the longitudinal frame members and the skin, thus reducing the necessary skin weight by spreading and cushioning impact loads and hence abrasion - Pakboats goes so far as to laminate the entire bottom panel of their hull skins with such foam to make their boats fit for extremely rugged expedition use. The Norwegian Ally boats display a similar approach. The use of different weights of skin fabrics and coatings in different areas of the boat, as well as the introduction of asymmetric coating weights inside and out, leave plenty of scope for further development.

Portability

Portability is still an important feature to many users of folding boats. The need to keep to a minimum the required storage space for a boat plays an important role for apartment dwellers-in fact many people would be unable to keep a boat if it were not for the fact that the folding variety allows storage in closets, behind doors and under beds!

There are some recent innovations worth noting: Feathercraft first introduced the back-packable K-Light and has now gone on to replace it with the Kahuna-similar weight (Feathercraft's new skin made this possible) and packed dimensions, but a longer, more serious kayak.

Klepper launched the Alu-Lite in the same vein. Folding canoe builder Pakboats presented the Puffin a little while ago, a small decked canoe also capable of relatively serious paddling.

Increasingly, boats are required to live in the trunks of cars, ready to be put together and launched whenever opportunity presents itself-and knocked down just as quickly for the drive home, too. Innovative frame compression systems (or, if you'd rather: skin tensioning systems), the intelligent use of inflatable sponsons, and
the introduction of reliable and water resistant deck openings and closures have already improved folding boat assembly and disassembly processes greatly. Klepper, through the use of highly refined frame fittings, has always had a reputation for being easy on the user in this respect. Nautiraid is exemplary in the use of modular subassemblies, which reduce the number of parts that the paddler has to connect. There is surely further scope for innovation on this front also.

Yes, there is plenty left to explore and improve and I, for one, am looking forward to an exciting future in the continued revival of folding boats-not least driven forward by a dedicated "underground" of home builders.