The importance of resin versus carbon fiber

[Captain Jim]

Originally Posted by Barb1

Hi Captain Jim,
I own the first Blackbird Savoy sent out to a customer and I have never had any problem with it's construction. It is a GREAT guitar!
Barb

Having played one at Kramster's place years ago, I have no doubt that the Savoy is a nice guitar. It was absolutely NOT my intent to imply otherwise. I was just recalling that someone who lived in a warm, humid area had an issue with their Savoy... which led to some discussion here about the e-koa vs carbon fiber durability.

[Sarah1F]

Originally Posted by tbeltrans

In Minnesota, recreational marijuana is about to be legalized. Maybe some entrepreneuring soul will decide to make guitars from hemp and use resin from all the bongs that will be fired up later this summer. It will be straight out of a Cheech and Chong movie.

I have already suggested to the rest of our condo association board that we invest in junk food vending machines to help with the cost of keeping the association financially sound. Personally, I have no desire to imbibe in either pot or junk food.

Anyway, back to the question - is the magic in the resin or the carbon fiber material? My answer - the question is best posed to those who work with this stuff - the experts. Over the course of developing expertise in my own career, I also came to recognize how little I know about so many other fields.

Tony

Dearest Tony, based on this response as well as some of your other responses within the carbon fiber thread/subgroup, I’m sure there are many of us who would love to hang out with you for even one day! Lol

[Marshall]

Originally Posted by mountainmaster

Maybe this forum could be called "Composit Guitars" to make it more inclusive.

I haven't voted, because I don't know. But I do get your point. I'm the guy that just ordered an ekoa guitar. I think the true nomenclature should be Composite. But there's too much momentum behind the Carbon Fiber forum to change horses names in mid stream.

But I think the broader issue for guitar building could be experimenting with man-made/altered materials to aid future lutherie. And I would think this would be a good place to post related discussion.

Afterall, carbon fiber guitar makers are adding wood veneers to their guitars. Talk about artificial?

[tbeltrans]

Originally Posted by Sarah1F

Dearest Tony, based on this response as well as some of your other responses within the carbon fiber thread/subgroup, I’m sure there are many of us who would love to hang out with you for even one day! Lol

Thank you. There was a recent thread on having an AGF get together in the Open Mic sub-forum, so who knows? Maybe that day will come.

Tony

[M19]

Yeah Tony, it’s high time we had one of those!

[tbeltrans]

Originally Posted by M19

Yeah Tony, it’s high time we had one of those! [emoji849]

...pardon the pun!

Tony

[LFL Steve]

A guitar made of CF without the resin would be like Chuck Berry’s gunny sack. Hardly a guitar. A guitar made of resin without the fiber would be like a hardened puddle of spilled paint. Also not a guitar. The magic of composites is that they have properties not present in their individual components. Wondrous properties in this instance.

Therefore the concept of relative importance isn’t applicable. Both components are mandatory, and so each is 100% important. Which is more important to water, the hydrogen or the oxygen? Which is more important to your chromosomes, the sperm or the egg?

[SprintBob]

Resin to laminate ratios are equally important in the discussion. Infusion or autoclave methods have a goal to use the minimum resin possible to wet out the laminate and fully extract the mechanical properties desired once the resin/laminate structure is cured. You also need to take into account if the builder is using a cored composite construction. Cored construction can reduce weight and increase stiffness. Any high tech composite construction is probably going to employ some type of core. The core used can be as important as the laminate and the resin chosen.

And that’s not all. How about pre-preg materials where the laminate is pre-impregnated with just the right amount of resin and stored cold. The pre-preg material is laid into the mold, could have a core material laid over the first layer, and then a final pre-preg laminate layer. This would then be typically cured with heat and vacuum (think autoclave).

[David Eastwood]

Originally Posted by SprintBob

Resin to laminate ratios are equally important in the discussion. Infusion or autoclave methods have a goal to use the minimum resin possible to wet out the laminate and fully extract the mechanical properties desired once the resin/laminate structure is cured. You also need to take into account if the builder is using a cored composite construction. Cored construction can reduce weight and increase stiffness. Any high tech composite construction is probably going to employ some type of core. The core used can be as important as the laminate and the resin chosen.

And that’s not all. How about pre-preg materials where the laminate is pre-impregnated with just the right amount of resin and stored cold. The pre-preg material is laid into the mold, could have a core material laid over the first layer, and then a final pre-preg laminate layer. This would then be typically cured with heat and vacuum (think autoclave).

One of the things I’ve loved about being part of the ‘alternative materials’ community these last five years or so is that, by and large, we all focus on the guitars themselves and not the minutiae of their construction.

Well-respected luthiers will continue to say that the builder is the single most important factor in a wooden guitar’s construction, and that, outside of certain specifics, the actual woods used are rather less significant than most realize. Despite that, the fixation on species continues, along with the associated confirmation bias and ocular auditioning.

I seriously hope we don’t degenerate into arguing about resin to laminate ratios, prepreg vs raw, and so on. That way lies madness.

It might be of academic interest, but if the guitar moves me and inspires me to play it, I really do not care how it’s made.

[Simon@Caulfield]

Originally Posted by SprintBob

Resin to laminate ratios are equally important in the discussion. Infusion or autoclave methods have a goal to use the minimum resin possible to wet out the laminate and fully extract the mechanical properties desired once the resin/laminate structure is cured. You also need to take into account if the builder is using a cored composite construction. Cored construction can reduce weight and increase stiffness. Any high tech composite construction is probably going to employ some type of core. The core used can be as important as the laminate and the resin chosen.

This is extremely accurate. Beyond this, not all laminates are created equally, weave pattern and fiber direction have a massive impact.

As someone who approached this from a Mechanical Engineers perspective, and not simply a luthiers approach; so many things are being overlooked and I have seen occurrences where false information is actively provided by manufacturers.

Im very analytical; and believe that any decisions should be supported by cold hard facts. I have now spent the best part of 3 years testing materials for my own instruments.

Just in terms of the resin to fiber ratio; and weave direction; here are the results of some test samples that i prepared and tested under load. The samples which strained (stretched a lot, extending out to the right of the graph) were tested where the fibers were loaded in a perpendicular or 45 degree direction.

The more vertical lines are composite samples where the load is applied in the direction of some or all of the fibers. Each line is an average of multiple samples, and the resin and method of layup is changed. Without getting into the weeds; i think it really shows how the "same materials", Carbon Fiber Reinforced Plastic, can display very different characteristics.

Feel free to send me questions regarding my testing etc. I'd be happy to make a more general video about carbon instruments and the various methodologies (i've tested most of them) if thats something you'd feel you'd enjoy. And if any of you want to send me your guitars to cut up and test the materials; i'm also happy to do that

[casualmusic]

Experimental composite instruments: fibre + liquid resin:







https://m.youtube.com/watch?v=nXQCek...ltIGR1ZXJpbmNr

https://m.youtube.com/@TimDuerinck/videos

https://m.youtube.com/@DAlembert-SU-CNRS/videos

[SpruceTop]

Thanks, Simon, for your informative comment!

[casualmusic]

Originally Posted by mountainmaster

I think there may be a small elephant in this room.

When we speak of carbon fiber guitars, we actually mean carbon fiber infused with epoxy resin. Without resin our guitars would be just flabby pieces of cloth. They need resin for strength and stiffness.

Blackbird Guitars has proven with their ekoa material that you don't need carbon fiber to produce a great sounding weather resistant instrument.

So what do you think is more important to the sound properties of the instrument: Resin or carbon fiber? My vote goes to resin.

I agree that choice of fibre structural material, choice of resin matrix material, and choice of manufacturing process are all needed.


Composite music instrument = structural material + matrix material (when needed) + fabrication process

. structural material (for strength) could be natural (cellulose paper, cotton, hemp, flax, etc) or artificial (glass fibre, carbon fibre, honeycomb core spacer, solid polymer plastic, metal alloy, etc)

. matrix material (if needed to solidify the structural material) can be natural (wood lignin, animal source paste/glue, plant source paste/glue, plant source polymer resin, etc) or artificial (liquid polymer plastic resin, lime, etc)

. fabrication process is how the components are created

. guitar makers choose a good combination of materials and processes.


Manufacturing processes:

Option I (traditional):
. thin panels cut/carved/bent
. solid wood, laminate wood, paperboard, dried gourds, aluminum sheet, steel sheet

Option II (high labour cost):
. layered reinforced plastic = fibre (woven or uni-directional) + core (if needed) + liquid resin + liquid catalyst hardener + fibre layup and resin process + curing process + smoothing process
. soundboards: RainSong, Emerald, McPherson, Composite Acoustics, Blackbird, Journey, KLOS, Enya X4
. back and sides: RainSong, Emerald, McPherson, Composite Acoustics, Blackbird, Journey, KLOS

Option III (low labour cost):
. molded reinforced plastic = solid pellets of polymer and short fibres + pellet melting and mold injection + curing process
. soundboards: Enya Go, Enya NEX, Enya ukuleles, Lava, Outdoor ukuleles, Donner
. back and sides: Enya X4, Enya Go, Enya NEX, Enya ukuleles, Lava, Outdoor ukuleles, Donner

Option IV (low labour cost):
. molded un-reinforced plastic = solid pellets of polymer + pellet melting and mold injection + curing process
. soundboards: Kala Waterman ukulele, Maccafieri ukulele
. back and sides: Kala Waterman ukulele, Maccafieri ukulele


Quality and performance are a result of guitar maker knowledge, skills and choices.


PS. eKoa = flax fibre + plant source resin


Best regards.

[tbeltrans]

The carbon fiber guitars I own consists of:

- Original CA Guitars Cargo
- McPherson Touring and Sable
- Emerald X20 and X20-7

Reading this from casualmusic's post:

Option II (high labour cost):
. layered reinforced plastic = fibre (woven or strands) + liquid resin + liquid catalyst hardener + fabric layup and resin process + curing process + smoothing process
. soundboards: RainSong, Emerald, McPherson, Composite Acoustics, Enya X4
. back and sides: RainSong, Emerald, McPherson, Composite Acoustics

Among my carbon fiber guitars, the CA Guitars and McPhersons sound very similar, but were (as I understand it) all designed by Ellis Seal. The Emeralds sound quite different and were designed by Alistair Hay. So apparently similar manufacturing processes, but very different results.

I have played a few Rainsongs, and they sound quite different from, Emerald, McPherson, and Composite Acoustics. But then they were designed by yet another person altogether.

So I conclude that, like wood guitars, each manufacturer of carbon fiber (or other materials) will have their own sonic signature sound. Also, all of these have a quite different feel to the player.

So once again in true AGF style, I have just built yet another case for owning some (not just one, mind you!!!) of everything.

Always glad to help...

Tony "the enabler" B

[mountainmaster]

Thanks for the input everyone! I have learned a lot.