The Dragonfly tube set was designed to build the lightest possible tandem bicycle frame without sacrificing stiffness, durability and ride quality. Calfee uses high modulus carbon fiber (66msi) in all the tubes. Previously, a frame built with all high modulus fiber would be too brittle but Calfee incorporated Boron fiber into the three main tubes to add some toughness and compressive stiffness. Boron is an attractive reinforcement because the resulting composite combines superior tensile, compressive and flexural strengths, high modulus, and low density in one system. Combined with the super high tensile stiffness of the carbon, the result is a frame material with the highest stiffness-to-weight ratio on the market.
The use of boron fiber has come of age with its use in Calfee’s high performance bicycle frames. Much of this weight savings comes with the use of carbon fiber composites. As bicycle companies compete in the arms race to make even lighter, stiffer bikes, safety and durability are pushed to the limit. High modulus (55 Msi and greater) carbon fiber is being used to make stiff yet thin walled tubing. These tubes can be vulnerable to damage from a variety of real world sources. When slightly damaged from a pebble thrown up by a passing car, or an unfortunate event during a group ride or race, a thin walled tube can rapidly degrade to an unsafe condition. The very popular Calfee Carbon Repair business is evidence of this common failure. Using boron filaments in the tube laminate mitigates this problem by significantly enhancing the tubes structural performance.
Calfee Dragonfly tandems deliver power as well as any large diameter, thin walled frame, has superior vibration dampening, compressive and impact strength, and is protected by a 25 year warranty, unheard of among carbon bike builders.
Dragonfly tandem dropouts are carved out to their optimal shape, saving 15 grams off the standard dropouts. This may not seem like much, but the way to build the lightest tandem on the planet is to address every component and look for opportunities for weight savings, no matter how small. The trick is to do it without sacrificing strength and durability. As in nature, the Dragonfly is one of the most optimized and evolved structures to be found.