Stevens Urethane Keeps Kayakers On The Go

Toughness Suits New Folding Kayak Design

Christchurch, New Zealand — Lightweight and portable is the name of the game in many product development circles these days, and a new brand of folding kayak is just the ticket for paddlers on-the-go. Weighing in at 7-10 kilograms (15-22 lbs.), FirstLight Kayaks, (Christchurch, New Zealand), fold down into a backpack-sized pack, can be assembled in about 15 minutes, and are designed for long-lasting durability and strength. TPU sheet from Stevens Urethane (Easthampton, MA) forms the kayaks' hull, and plays a key role in performance and weight reduction.

"We developed our kayak in response to demand for a folding kayak that performed and handled like a true kayak, and that was also light enough to be easily handled and carried by anyone," said Martin Ross, Chief Executive at FirstLight. Competitive models can weigh more than 15 kg (33 lbs.), and while most people can carry a 15 kg kayak, Mr. Ross notes that handling and transporting one along with other baggage isn't easy." To produce a kayak that was both light and strong, we used high quality materials and some innovative design approaches."

One of these innovations was creating the hull from a single sheet of Stevens Urethane ST-1880. Urethane is tough and elastic, with elongation up to 200%. This elasticity offers two important benefits: it permits the entire hull to be cut from one piece of material, eliminating seams under the waterline; and it minimizes the chance of rips and tears. If the kayak hits an object, the hull will simply stretch at the point of impact, then go back to its original form.

"Performance was the key criteria," noted Mr. Ross, "and for our hull that means dimensional strength, elasticity, puncture and abrasion resistance and UV resistance. We can't afford for the material to fail."

Stevens Urethane ST-1880 meets all these criteria. It is a UV stabilized, 87 Shore A polyether aromatic thermoplastic polyurethane with excellent physical properties and sealability. It is inherently stable when exposed to high humidity, with natural fungus resistance and superior low temperature properties.

In use, the hull must be puncture resistant and strong enough to withstand the scrapes, abrasion and impact of beach launches, shallow water paddling, and contact with submerged objects. Stevens Urethane provides the necessary strength and abrasion and impact resistance, and maintains its performance properties despite exposure to water, temperature extremes, and UV rays.

Storage conditions present other challenges for the hull material as well. The kayaks are typically stored folded up inside a pack or box the size of a normal hiking pack. The skin (hull and deck) must fold and unfold repeatedly for years without creasing or weakening along fold lines. Because TPU has no placticizers, it will not become brittle or lose its flexibility over time, or when exposed to temperature extremes.

"The TPU hull will resist abrasion and scuffing for many years, and not weaken or split despite repeated cycles of use and storage," said Mr. Ross. He adds that in the unlikely event that it does get torn or punctured, TPU does not run (enlarge) and it is easy to repair both temporarily in the field and permanently once home.

"Stevens Urethane helps us manufacture a kayak with optimum strength and durability, while maintaining the lightest possible weight," said Mr. Ross. "Its elasticity conforms to the 3-dimensional underwater section of the hull in one seamless piece, helping reduce the weight of the canopy. Furthermore, TPU is energy absorbing, so if the kayak is placed on a rock, it will yield without placing excessive loads on the seams."

In addition to the hull, FirstLight kayaks include a fabric deck, foam technology in bow and stern, and frame components made from composite tubing for maximum hull stiffness and minimum weight. The urethane hull is sewn to the composite fabric deck of the kayak; both hull and deck are cut and sewn according to patterns developed for FirstLight by a sailmaker, and tested thoroughly for watertightness. Design techniques to tension the skin eliminate the need for heavy, bulky air pumps The resulting kayak is light, strong, and suitable for most recreational and touring paddling situations.

"We guarantee our boats for 2 years," said Mr. Ross, "but we expect skins to last 5 to 10 years depending on how often they are used and how well the owner maintains them. Urethane gave us the premium performance we needed."

Based in Easthampton, Mass., Stevens Urethane manufactures a full range of high-performance urethanes for use in a wide variety of "can't fail" applications for consumer, medical, commercial, and industrial markets. Stevens Urethane is the only company in the world to offer urethane in blown film, extruded sheet, tubing, cord, and profile form.

For additional information, contact: Stevens Urethane, 412 Main Street, Easthampton, MA 01027. Phone: (413) 533-8100, or toll free at 1-877-TPU-FILM (1-877-878-3456). FAX: (413) 552-1195. E-mail: info@stvure.com. Stevens Urethane is a business unit of JPS Elastomerics.