Though built for stability, some carbon-fiber bows warp. Why is that?
—Paul Peterson
Bow maker Jeff Van Fossen responds:
A: A bow’s camber—or the curve of the bow stick—is critically important to its performance and camber adjustments of less than a millimeter can dramatically affect the feel and response of a bow. Traditional makers spend considerable time adjusting the camber of their bows before considering the bow complete.
Because a cambered piece of wood wants to straighten out to its original shape with time and use, it will eventually “lose” camber with normal use. For this reason, a bow maker should periodically inspect a wood bow, and if needed, discuss re-cambering the bow with the owner so that the bow maintains its original performance. A properly made carbon-fiber bow will theoretically retain its camber forever under normal playing conditions. However, in practice, this isn’t always the case.
Carbon-fiber bows are made using a different process than traditional wooden bows, and if made precisely and with high-grade materials, its camber will be inherently stable and the bow will not migrate from this original shape. A well-made, high-performance carbon bow is comprised of high-quality fibers and engineered resins made in a highly controlled process. Together, these ingredients can create a well-cambered, stable bow shaft that can deliver a lifetime of performance.
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But, this is not always the case with some of the carbon-fiber bows on the market. So why do some carbon bows warp or lose camber and can anything be done about it?
High, aerospace-grade fibers and engineered resins ensure that the fibers and resin bond properly, thus allowing the part to benefit from the properties of both fiber and resin. This maximizes the bow’s resistance to drifting camber or straightness also known as “creep.” If lower-quality ingredients are used, the shaft will be less resistant to creep, and it will ultimately yield to time and use, gradually warping or losing its camber.
It’s possible to heat the shaft to a softening point and to straighten or re-camber a carbon bow. However, this is risky to the bow and ultimately only a short-term fix because the part is still not resistant to creep, and it will eventually warp again.
Correctly making a carbon-fiber bow is critical to its long-term stability. When I make bows, a crucial step is the point when the fibers are woven into the shaft and the resin is introduced and cured. If this step isn’t done properly, the bow will be born warped and out of camber. Unfortunately, the bow will want to stay in this warped state, so the best thing to do is reject and discard the bow instead of trying to fix it with a temporary re-cambering.
If the bow is re-cambered, the player will purchase a bow that appears to be straight and stable only to see it eventually warp and lose camber.
Because it is very difficult for a player to assess bow integrity at the time of purchase, the ultimate solution is to look for trusted, time-tested brands that back their bows with excellent warranties.
Jeff Van Fossen is an engineer and violinist who designs and makes carbon-fiber bows under the CodaBow brand in Winona, Minnesota.