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Responsible Weight Reduction
Exegi strives to use the highest quality materials and advanced composite techniques to try to reduce weight in a responsible manner. Exegi understands the importance of reduced mass in achieving high performance. This is tempered by the fact that even with the highest strength materials assembled as carefully as possible at a certain point skis and boards become fragile when exposed to things like rocks, stumps, tomahawk style crashes, and the like. We prefer to utilize the impressive strength and stiffness of carbon fibers to achieve the performance customers want in responsibly lightweight packages.
Carbon Fiber's Siren Call
A quick glance at a table of material strengths and stiffnesses including carbon fiber, steel, aluminum, fiberglass, boron, flax, silk, etcetera, will quickly lead the aspiring ski and board designer to twitch in anticipation. Carbons superior mechanical properties point to the possibility of light weight and adequate stiffness and strength. Given the basic fact that, all else being equal, lighter is better tends to lure the designer towards reducing mass. Carbon fiber’s highly directional nature allows for tuning flex in different directions (torsion vs longitudinal stiffness for example). These promises, however, are fraught with danger. The temptation is to design the ski/board with enough stiffness and strength to do the job. This can be achieved at somewhat riduculously low weight. This is especially true if one is willing to utilize lightweight core materials (honeycombs, balsa wood, Pawlonia, Cedar, or foams). One has to tread carefully.
What could go Wrong?
The problem is that there is simply not much of the strong stuff in the ski or board. That is the layers of structural materials are thin. Further, the cores have little resistance to point loading. This leads to the situation where, for example, a perfectly fine ski or board has a gaping “can-opener" wound from meeting up with a pointy rock, or an agressively flexed board dimples the core at the binding edge. These lightweight woods are highly hydrophilic. Water, when introduced through a core-shot or corroding binding screw, has a tendency to wick agressively into surrounding wood and then rot with shocking speed. The use of honeycombs and lightweight woods in cores necessitates further care in manufacturing. They won’t hold a thread so further point reinforcement is required for binding retention, they can be difficult to machine accurately so control of core thickness is difficult (though not impossible). Further, when trying to reduce mass, one has to try to control fiber to resin ratios accurately or the effort can be wasted by replacing the weight savings with extra resin. Those highly spongy/hollow cores tend to “soak up" resin or cells tend to fill in. This can in the best case lead to slightly heavier structures, or in the worst case, the correct amount of resin is used, but then gets soaked up by the core/runs off the honeycomb “edge" leaving a poor core to face bond. Failure is imminent.
Exegi has years of experience with lightweight cores (especially Balsa) and carbon fiber, Kevlar, and other high performance fibers and we have come to the conclusion that the best approach is a sort of “golden mean". Utilizing slightly more carbon fiber than is currently in vogue, combined with a medium weight custom laminated core allows for middling lightweight skis and boards that have better resistance to damage and longer life-cycles than skis/boards built with traditional materials while delivering better performance and strength/stiffness to weight ratios.
Because every ski or board is custom build to individual user design cases Exegi can build extremely light or extremely durable product depending on what the customer wants. Our customer consultation process ensures that customers get what they need, and what they want. Further, the consultation process helps the client understand and take part in the process of getting the best carbon fiber ski or board for them.