Playing with carbon fiber

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Playing with carbon fiber

Postby Joshua Collins » Wed Aug 22, 2018 1:30 pm

Ladies and gents, get your finest rotten fruit and veg to hurl at this one. As this forum strikes me as the place where only the finest of handcrafted artisan work goes on, I can only imagine the 'booo's' and hisses will come when I mention the three dreaded letters. :lol:

CNC.


I used to own a Zon and a Modulus bass and loved the necks on them. I'd like to build myself a 4 string J-style bass in the same sort of style as the Modulus VJ. Beyond the theatrical writing as formerly noted above, I wonder, how many of you fine people have had experiences playing with carbon fiber? Would it be worthwhile to do a design in a CAD program and send it off to be CNC'd? Thanks for reading. :)
Sounds:
https://www.youtube.com/watch?v=twkkCD9ybhw


Mods, I've just realised I've posted this in the wrong subforum. Apologies.
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Re: Playing with carbon fiber

Postby Steve Sawyer » Wed Aug 22, 2018 2:42 pm

Joshua - I've never heard of anyone machining CF. CF is very much like fiberglass, laid up in woven sheets with a 2-part resin. OR are you suggesting using CNC to create the mold for laying up the carbon fiber?
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Re: Playing with carbon fiber

Postby Joshua Collins » Wed Aug 22, 2018 3:06 pm

Steve Sawyer wrote:Joshua - I've never heard of anyone machining CF. CF is very much like fiberglass, laid up in woven sheets with a 2-part resin. OR are you suggesting using CNC to create the mold for laying up the carbon fiber?


I guess you learn something new everyday! I was originally under the impression that CF could be CNC'd much alike many other materials. Perhaps it'd be better to CNC a template for the mold, so to speak? Cheers, Steve. :)
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Re: Playing with carbon fiber

Postby Steve Sawyer » Wed Aug 22, 2018 3:37 pm

I am not any kind of an expert - most of my expertise on machining comes from calling my son, who IS a machinist.

However, it appears that CF is machined, but from some searching on the 'net it looks like it's only done to get a part to final dimensions as discussed here.

If laying up a CF shape, you would probably leave it hollow, otherwise it will be much too heavy for a guitar neck (most of the weight of CF comes from the resin, not the carbon fibers), and I'm not sure I would want to try to engineer a hollow shape to withstand the stresses of the strings in tension when tuned to pitch. If the thickness of the CF varies too much, the string tension could also twist it instead of bowing it. You'd also need something to accomplish the same task as a truss rod to adjust the relief. All in all, it sounds like a pretty complex undertaking.

That said, there are some (even some around here I believe) that have used CNC routing to shape necks. It's a real challenge, and you can probably carve a neck in half the time it'd take you to program a CNC router to do it (maybe even much less than that!) but it's the kind of thing that folks see and enjoy as a challenge.

Not sure what you're after with the CF, but if it's some added mechanical stiffness, you could really create a challenge for yourself. CNC carve a neck AND a form to match. Then, lay up some carbon fiber over the carved neck, and sandwiched between the neck and the form. This would give you a uniform layer of CF, and a surface that could be sanded and polished. A CF neck would definitely be a striking design element!

Oh - one other thing. When thinking about machining (a subtractive operation) consider an additive operation - 3D printing. The company I link to below will 3D print in aluminum, steel and several different kinds of plastic. They can accept Sketchup files to print from. You might not want a neck 3D printed (though an aluminum neck would be an interesting experiment), it might be suitable for making forms for laying up CF.

https://www.shapeways.com/
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Re: Playing with carbon fiber

Postby Randolph Rhett » Thu Aug 23, 2018 2:10 pm

I use carbon fiber in my guitars, although they are acoustic instruments not solid body electrics. It would never occur to me to mill a block.

First, the largest solid block of carbon fiber I’ve ever seen is a 3/4” pultruded rod. I can’t even imagine a solid block large enough to mill into a neck —or the cost! Could you CNC a bar of gold into a guitar neck? It’s technically possible.

Second, carbon fiber is murder on a sharp edge. You woul probably have to stop your CNC every 30 seconds or so to put a new sharp bit in.

As previously posted, carbon fiber is mostly used as a woven fiber sheet hardened in epoxy. It works like a super strong and light weigh fiberglass.
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Re: Playing with carbon fiber

Postby David King » Fri Aug 24, 2018 2:47 am

I'd look at a neck from Moses Graphite before reinventing the wheel as I've always found them to be quite reasonable. They have a Fadal 4020 or it's modern day equivalent which they undoubtedly use to make the molds and trim the finished necks and other components that they make. From what I can tell their necks use a CF "backbone" with a resin "flesh" cast around it.
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Re: Playing with carbon fiber

Postby Steve Sawyer » Fri Aug 24, 2018 6:53 pm

David King wrote:I'd look at a neck from Moses Graphite before reinventing the wheel as I've always found them to be quite reasonable. They have a Fadal 4020 or it's modern day equivalent which they undoubtedly use to make the molds and trim the finished necks and other components that they make. From what I can tell their necks use a CF "backbone" with a resin "flesh" cast around it.


Moses Graphite appear to have exited the guitar neck business according to their website. :cry:
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Re: Playing with carbon fiber

Postby Brian Evans » Sat Aug 25, 2018 12:36 pm

My experience with carbon fiber was watching how people built race car parts. make a mold, for which CNC was used extensively, do a layup getting cloth type and weave direction right per the engineer, vacuum bag/autoclave and bake if pre-preg, or do a wet layup if no oven. We did get sheets of flat carbon fiber laidup material that we could cut to make flat parts. In the context of a guitar neck, I think people make a light wood core, do a wet layup and vacuum bag it. With wet layups getting the resin out is the hardest part, you want as little resin as possible, but just enough. I don't know if you could do an autoclave/oven cure with a wood (or maybe structural foam) core, but I bet someone is doing it.
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