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Comment by tkgally | Hacker News Reader

Do any string instrument players here have opinions about the differences between wooden and carbon fiber violins, violas, cellos, etc.? I’ve watched some YouTube videos comparing them, and I can’t hear the difference. I imagine the sound and response might seem very different, though, to the performer.

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They're OK enough as a travel instrument, but they don't sound particularly great because no manufacturer has taken composite technologies seriously. They're using archaic manufacturing methods (wet layup and vacuum bag) that produces a composite with too much resin - more plastic than carbon. They cannot properly control the acoustic properties of the material, because they can't control the material period.

If you see the a high-gloss finish and a characteristic woven pattern, you're looking at a showpiece rather than a serious instrument. That's not what a high-performance composite looks like - you should expect to see the satin finish and linear "grain" of unidirectional pre-preg. I'm yet to see that on any musical instrument.

What does satin/gloss finish have to do with anything? That's a choice made at the finishing stage as to what clear coat to put on it for uv protection and scratch resistance. And while uni might be appropriate for parts of the violin, you still need to orient plys in multiple axis for flexural strength, so you might as well do some of that on the outer cosmetic layer to make the product more appealing to consumers.

Viscoelastic polymers are poison for stringed instruments, because they have very high damping coefficients. They turn the precious vibrational energy from the strings into useless heat. Only cheap mass-produced instruments are finished in polyurethane; quality instruments of traditional wood construction use a shellac-based finish (sometimes nitrocellulose lacquer on guitars), which have lower damping and can be applied more thinly in practice. In the context of high-quality instruments, the difference is not subtle.

Wood instruments need a finish to protect them against moisture, but that isn't an issue for CFRP. Any finish - especially the kind of thick finish you need to get a high gloss over woven reinforcement - makes the instrument worse for no benefit other than cosmetics. If you would choose a shiny instrument over one that sounds better, you're buying a showpiece rather than a serious musical instrument.

Epoxy is a necessary evil in CFRP, but we want the absolute highest possible fiber volume ratio. Unidirectional or spread-tow reinforcement will always allow for a higher fiber ratio than woven material.

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