One company whose skis are widely used for backcountry skiing and alpine touring is New Zealand-based C6 Skis. C6 makes skis using its Autoclave Cured Carbon Prepreg (ACCP) technology. Typically, CFRP skis are constructed using a wet lamination process involving carbon cloth soaked in resin and sandwiched together. This, according to C6 founder Craig Stirling, results in a resin-heavy laminate, adding excess weight.
The C6 ACCP ski sandwich is laminated using a unidirectional prepreg carbon fiber supplied by Gurit. The ski’s laminates are laid up in a rectangular block, and the upper laminate has a layer of twill weave carbon cloth applied to it. Then, the upper and lower laminate are cut from a pattern to C6’s desired ski shape. The upper laminate is applied to the upper mold, while the lower laminate is applied to the ski’s 1.4-millimeter polyethylene base and then applied to the lower mold. Next, the laminates are vacuum bagged and cured in an autoclave at 80 C at 7 bar. The high pressure, Stirling says, ensures the finish is perfect. The laminates are then demolded and cleaned up.
For core material, C6 uses end grain balsa. The balsa core is machined to a tapered profile to control the longitudinal flex of the ski. The laminates are applied either side of the core, dried and then placed between the upper and lower molds. They are then vacuum infused and bonded with Adhesive Technologies’ HPR5 toughened epoxy while in the autoclave at 5 bar. The skis are then removed from the mold, cleaned up, waxed and ready for use.
Challenges and Future Outlook
While many in the skiing industry are singing the praises of prepreg CFRP, the same “pop” that skiers love can quickly turn into excess vibration. Hunt also acknowledges that the material can be difficult to work with. As Stirling explains, manufacturers tend to have problems controlling the finished shape of CFRP skies because it can be difficult to get the carbon fiber to contract with the resin while cooling. This, in turn, slows production.
While there aren’t many methods available yet to ease the carbon fiber contraction process, DPS is currently working to address vibration issues with its “Alchemist,” a new line of skis that pairs the company’s signature prepreg construction with proprietary dampening methods.