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I have been thinking about my next build. I have been tossing around the idea of using carbon fiber for the sides. Any opinions on the use of this stuff? I know other guys build complete carbon fiber guitars. I didn't really appreciate the sound. I am planning on using a koa back with BRW bindings. I am not sure of the top material yet. If you have any suggestions on top my material please share them. Thanks!

Rob

Rob-
Carbon fiber cloth is pretty nasty stuff to work with, and expensive to boot. (My experience is limited to helping with a couple of CF jobs around boats.)
It will wreck most tooling in short order as well. (I recall you need carbide scissors to cut it??)
I use laminated wood sides and once I put a layer of 6 oz fiberglass between the laminations because I was worried about the very curly sides splitting....but never considered CF cloth.

Cheers
John

I have some experiance making molds and casting with this stuff. I am a little concerned about the binding process and the looks of this. Do you think it would look weird? As for the cost I have some left over materials from a job i did at work that i am planning on using for this task.

Of course, you all know that folks are building carbon fiber guitars. But I have to say this is an interesting idea. Wood where it matters and CF where it foes not matter. Cool idea.

It is an interesting idea.
You obviously know what your are getting into with CF, molds, resins, etc so you are many steps ahead of most of us here.

As you say, it's figuring out how to do binding (if any) and work the transitions between the CF and the wood that will be tricky.
Another possibility would be to do the back and sides in CF- sort of like 'an Ovation done right'.

This is going to be a steel-string acoustic?

What didn't you like about the CF guitar you heard?

It sounds like you've worked with the stuff a little so you know what you're getting into.
I can't decide wether it would look great or odd myself.
You could end up with some fairly rough binding cuts, but maybe a black pufling line between the carbon fiber and binding would help blend it.
You could also have finishing issues depending on the mold release you use, but a good cleaning and a shellac seal coat should help that.

_________________
Jim Watts
http://jameswattsguitars.com

You could make the sides with the binding channel already molded in and avoid any routing whatsoever.

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

I played an all carbon fiber guitar that once was showcased at American Music in north Seattle. It was muddy pretty much across the entire bandwidth. I imagine having an actual wood face, back, and neck would have improved this aspect but I also expect that it would take quite a while of fiddling with various weaves and aerial weights before one understood the variables that affect tone if one were to persist in making composite instruments.

You can alter the thickness of wood if you want....you can only adjust aerial weight and resin content with carbon....and these are gross adjustments that prohibit subtle adjustments.

Personally, I've designed and fabricated more projects with carbon fiber, kevlar, and glass than I care to think about anymore. The buzz word "carbon fiber" lost its appeal to me 15 years ago but I see a LOT of people that like to borrow this buzz by using carbon fiber in their products. Many of them don't understand the mechanical properties of the material...and use it incorrectly. So that seems a little silly to me but I don't suggest it doesn't have a place in guitar construction. The question I have is, "Why use it?"

1. To preclude the necessity of bending side wood? Yep....that's a good reason. I could certainly come up with a mold to make carbon fiber sides a LOT sooner than learning to bend wood...given my background. I might also consider a one piece molded side that included the kerfing. And not just include the kerfing but mold the part such that the kerfing was perfectly flat on the open gluing edge…..and incorporate a wooden neck and tail block while I was at it…..the possibilities continue.

2. To create stronger sides? That’s a good reason too, although the part could fail if it’s not designed properly. Wood sides are strong because they are curved, which allows far more capacity to bear certain loads without buckling or cracking. To design carbon sides without fully understanding these loads would involve some trial and error. I would suggest a uni-directional layer (150 grams per sq. meter) oriented along the length of the side, sandwiched between two light (3-4 oz. plain weave cloth) layers would be significantly stronger along and across grain than wood...if processed correctly.

Eliminating the uni-directional and using a .05”-.075” thick foam core material instead would also be stronger than wood but it might also dampen vibration…..which it most certainly did with composite aircraft propellers….good with propellers, maybe not so good with guitars.

This assumes you can control resin content when processing this material to yield a resin/fiber ratio that doesn’t flirt with the 40% mark for resin. Ideally, 32% or so + or - / a few percentage points is the place where the published mechanical properties are reliable. Not that you re going to “engineer” this piece but if you go too far with the resin, you add weight and take away strength.

3. To have a guitar showcasing “carbon fiber”? As a gimmick, it might sell some guitars. Who knows? I certainly had no regrets about leaving that carbon fiber guitar sitting on its stand at American Music….unpurchased. It was ridiculous at being a guitar.

The memory of that plastic guitar made me think of a hundred other products that were created, not because they would function and therefore, be useful to someone else, but because someone had a personal notion and needed to satisfy their curiosity. I don’t judge such pursuits unless the cost of following an idea ends up being borne by someone other than the author of the idea. I can string twenty stories together highlighting this very mode of operation (other people’s money) in the aviation field.

But this idea could actually work. You might end up with something that really is a functional improvement. Personally though, if I never see that weave pattern imprinted on my retinas just prior to dosing off again in my life, and instead see the infinite variations of wood grain, I’ll wake up happier each morning.

Wood is simply prettier than carbon fiber.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Thanks, Stuart! Interesting stuff there!
The CF 'craze' is a funny thing- if you look around you can see CF 'lookalike' more and more in cheap products- either black fabric in resin or fiberglass in a black resin. And don't get me started on the $15K 'upgrade' to that new Porsche which provides CF instrument panel surrounds......



John

Indeed interesting to hear from a pro. I've pondered the idea of CF sides with wood top/back myself, in fact. And to improve the look, how about adding one more outer layer of wood veneer? If you cut your own sets, you could get a lot more mileage out of a board for sides. Still ugly on the inside if you look closely, but not as ugly as those carbon rods running all over the place in some soundboxes.

Looking forward to the results if you try it!

I've got most of my interest in using CF for large guitar components out of my system but what about using pre-preg CF for sides. Would that make things easier?

John

Actually the great utility of this idea would be that only heat would be required to finish form the sides and the final part would be a perfect fit to the final mold.

Assuming a thin layer of veneer is much, much easier to heat/steam form than a thick one, adding a layer of carbon to the inside of the sides after the initial heat/steam bending of the wood would create a final process that would require only heat...no moisture. Once the fiber is cured and cooled the carbon would work to hold the shape far more than a thin layer of veneer.

I imagine holding the designed body shape and avoiding bending breaks are main challenges to side bending. This idea could eliminate both issues.

There are a number of things that could be problems with this. The main one I can think of is epoxy saturating through the veneer unpredictably. If using epoxy to pore fill this might not be an issue but one would probably have to seal the veneers prior to molding the fiber to the pre-formed wood in order to avoid this.

One could sandwich a fiber layer between two layers of pre-formed veneer. Seems like a hassle....but it would never crack compared to a solid wood side of the same thickness and no one would ever see it.

Of course….I can hear the grinding teeth of those purists out there and I’m inclined to agree and note a distinctly unnatural aspect to this whole conversation. I’d only use carbon in an instrument where it was plainly the best choice from a mechanical load bearing standpoint, and then only if it clearly had no adverse influence on the tone. If I couldn’t hide it underneath a veneer and basically….bury it….I think I’d go a more traditional route.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

You know I am still tossing around this idea. For me the benefits for this venture is
1) I have some koa sets that I plan to use for my next build, and honestly I am
not looking forward to bending this stuff.
2) If this were to look ok I may be able to avoid some of the lumber hunting. Finding back material isn't half as bad as finding side material.
3) I might be able to save cost of material by cutting thinner veneer stock for my sides. If I didn't like the look of CF.
4) I would be able to come up with more dramatic shapes without being limited by what I can bend, with repeatable results.

I am not planning on using CF for anything other than the sides. I know it's possible, but I would like to try and walk the line of composite and organic a little closer to the organic side than some had tried before. This may sound a little naive, but I don't think I would be able to hear a difference in tone by using cf side versus a wood side. As far as cost it is probably a wash. After calling and emailing every exotic wood store I could find for some curly koa to resaw, I now am trying to look for different options. As far as structure goes I wasn't as concerned about achieving a certain structural goal. I was planning on using the appropriate weaves ( I was thinking about doing 4 layers) and vacuum bag my mold and call it a day. I may be missing something but most of anything I have molded with fiberglass not even CF were definately stronger than bent wood sides

First off my guitar building experience is limited, however i have worked with fiberglass and carbon/Kevlar quite a bit.

It would be easy enough to build a plug/mold to form the sides off of. Its always best to buy prepreg carbon if you haven't used it before however it may be difficult to procure a small amount that you would need. I would as other suggest mold in the purfling/binding channel. Plug could be built like a fox style bender template and built up with bondo then sanded smooth, dont forget the mold release compound, I've made that mistake more than once.

In college we built solar powered boats out of carbon, we always laid up our own for small stuff, like the props, actually we used a crude form of injection molding for these. In any case you have two choices to cure, vacuum pump in a bag for small parts that you layup by hand or oven bake for prepreg. We got lucky for our boat we happen to find a guy in the area that worked on F1 car bodies so he had a walk in oven.

I would probably look at using a nolmex core of some kind (honey comb shape) to add some strength in and out of the sides (parallel to the top.) Its really fun stuff to work with, very strong for its weight, and there are multiple weave patterns to choose from depending on the way you are loading it. Keep in mind that composites are always a material suspended in a matrix, and the matrix is the weak spot, you want to minimize the amount of resin while still making sure to suspend the weave fully.

Even if it doesnt make a great guitar, i think it still would be a very fun project, simply in terms of how to fit it all together and get good joints

I was out at Nazfest this weekend and played a high end carbon fiber guitar. It was a dred size and we all agreed that as for a boat paddle ,it would be fine. The guitar had no life and was rather boring sounding. There was just no life in it. I agree if you want to make something for travel and that can take abuse CF would be fine . If you want a real guitar you need wood. I know torres built one of paper mache as did a few others but that is a wood based product.
Still It may be a good exercise for you. If you want to do it , you may learn things you wouldn't have learned if you didn't

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Maybe the easiest way to work the CF would be to lay a single layer of cloth out on a prepared smooth surface, such as glass. Once it is cured, use accurately prepared side patterns to trace out the sides and cut the cloth with scissors, you'll get a nice clean cut line. Take the cut pieces to your mold and bend them into place. A single layer will bend easily. You can then add some more cloth to stiffen the sides, maybe fiberglass as it is easier to shape.

Wood really is pretty easy to bend and work when all things are considered.

Good luck.

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Expectation is the source of all misery; comparison the thief of joy.
http://redrivercanoe.ca/