Custom CF Wood Hybrid 2.0
 

Hello.

This thread is a continuation of this thread (per request of the mod) :

http://www.acousticguitarforum.com/f...48#post4400248

This thread is about a guitar model called the Hybrid 2.0. It used carbon fiber and fiberglass as well as wood for a balanced instrument and soundprofile. The back + sides + neck + head are all 1 laminated composite component, the entire front is made from wood, as well as internal wood.

I am currently in the stage of building brand new tooling. Hybrid 1.0 had a failed crowdfunding, but then i got a 10000 Euro loan, that is why i am bringing this model to the next level in terms of quality.

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Layer 2 of gelcoat.

Had to wait 8 hours. I want another coat on this,maybe even 2, so that means i have to set my alarm at 4 o clock at night, or stay awake. Chemicals have to be treated as described in the instructions manual. It takes as long as it takes.

https://scontent-ams3-1.xx.fbcdn.net...24767325_o.jpg

Rought cut the soundboards :

https://scontent-ams3-1.xx.fbcdn.net...02896844_o.jpg

The headstock plates come out of the actual tops :

https://scontent-ams3-1.xx.fbcdn.net...8a&oe=57D91214

https://scontent-ams3-1.xx.fbcdn.net...69368242_o.jpg

I think my eyes are blinded by gel coat!

Is there any post-process work needed on that gel coat once it's cured?

Haha, its pretty bright! :)

Yes. First 24 hours on room temperature then 15 hours at 60 degrees Celcius. I called the company, he say i should apply all layers and then put the heat on in. I asked if i should heat on every layer, that was not the case so I timed 24 hours starting at the gelling of the last layer (i put 3 layers of this gelcoat on).

The plug has edges on it and a lid with 2 electic ovens will provide the heat for 15 hours.
https://scontent-ams3-1.xx.fbcdn.net...17879850_o.jpg


This is a plug so the negative will be upside down, a mold with a guitar shaped hole in it.

Yes, saw that in the previous thread... I guess I was referring to any sanding, polishing, or such that needs to be done after the gelcoat fully cures.

@LouieAtienza I expect some surface repairs will be necessary. If there are pinholes, they need to be filled. If you detect an airpocket between the gelcoat and the fiberglass backing, you have to drill a hole and fill it with expoxy glue.

I expect that the raised area for the reusable vacuumbag seal has some places that need to be repaired as well. The plugs sealing clearcoat started to seperate from the wood because of a chemical reaction with the high temperature release wax (you can`t plan for things like this), so i think it will have a rocky surface in some places. You then have to sand it to make a rough surface for bonding and then apply gelcoat and sand it flat.

Todat the curing of the gelcoat went completely wrong, the back was starting to arch up, creating an airpocket between the plug (guitar shape) and the molds surface. I had to choose between ripping the gelcoat off and ruining it (150 Euro loss), or continue with fiberglass backing for dimentional stability, i chose the latter. I can not afford to loose these materials, there is no backup and it`s on a loan. If this fails i will have a direct loss of more then 500 Euro in materials, but if there are no guitar bodies i will loose 10000 Euro, and i will be paying back for the next 10 years. In the best case scenario, the back had an arch 2 millimeter more then planned. 2 Millimeter is a lot if you spend 6 weeks perfecting a shape. In the worst scenario, there is a weird line or edge, i wont know untill this is seperated. I will know in 1 to 2 weeks. If the back is arched 2 mm more then planned, i can live with it, as long as it`s even and without a weird edge.

It didnt even reach 60 degrees yet in the box, i think the heatsource was just to close, the issue is only in the back of the guitar, the rest is still making contact, thankfully.

Here is a movie demonstrating the undesirable air pocket between the plug and the mold surface : https://www.youtube.com/watch?v=meX3...ature=youtu.be

This movie is right after i discovered it, it was about 5 millimeter then, it schrunk back to a 2 mm gap now.

First layer of fiberglass with sprayglue (not yet saturated with resin)..

https://scontent-ams3-1.xx.fbcdn.net...19743491_o.jpg

This has roughly 3 layers of fiberglass, every layer required almost 1 kilo of epoxy to fully saturate, this is costing alot of money, and its not done yet.

https://scontent-ams3-1.xx.fbcdn.net...24863899_o.jpg

Ideally, you want to put this in a giant vacuumbag or an expensive autoclave machine to compress all the layers to make sure there are no airpockets between gelcoat and fiberglass or between layers of fiberglass. Such a bag or machine is not in reach now, financially. This 10k loan is a stripped down version of a 30k plan.

This composite stuff is a true A - B - C thing, if you mess up anywhere in the line, it affects everything, and can ruin everything.

There is no time for whining, just have to make due and keep the project on track.

How would one go about building a hybrid with just the sides as CF? Deadtree guitars does this and I was always interested but I don't quite understand how he does it. Most, if not all, luthiers agree that the sides are acoustically dead so strengthening it by using CF would make a lot of sense.

I once applied 1 layer of carbon on the inside of an Antonio De Torres replica, you can do that with wetlay. That is a brush and epoxy.

If you want to make a 100% carbon rim (a.k.a sides), or even carbon with fiberglass, then you need a mold. The fabric that touches the mold surface will be the shiny, nice side so you need a negative mold. So it would look like the wooden mold you use to put normal bent wooden sides in (not my picture).

http://i.imgur.com/VPO4XOw.jpg

You seal it with clearcoat, then sand it 100% flat, then put release wax on it then you can use spray glue to attach fabric how you want it and then you wet it out with epoxy. If you want to do it without spray glue, you wet the surface out with epoxy, then put the carbon, and some more epoxy from the back. There are more elaborate and expensive ways like infusion but i would not recommend starting with that. A vacuumbag is recommended to suck the fabric against the mold.

If i was gonna do this i would build in a neck pocket into the composite component, to put a wooden neck in with its tail. You slide it in top to bottom. If you do this or not, you should get 1 continues piece of fabric that starts and ends at the neck pocket, so there is no visible seem.

The setup on this would be $25 for wood, $100 for carbon and epoxy, $50 in disposables (glue, gloves, mixing sticks, a scale, a container etc). I would recommend a fiberglass core between 2 carbon layers to save money.

Once you have a cured part, you open the 2 wooden pieces with the hinge, take it out. I would glue sandpaper on a board and sand both sides flush (with a facemask!).

You can`t rouyte binding channels in the carbon or your bit is dead. If you have a mold that flips open, you can build the ridges in the mold so there is a carbon edge to glue bindings in. It has to flip open for this or the part can never leave the mold. You can also just sand both sides flush and glue the linings in the body "to high". Then you can glue the soundboard on, and just route binding channels into the wood and not the carbon.

Good, it will be more of a fun read without 'this is costing alot of money'. ;)

You're awesome. Thanks so much for the very detailed response! It does sound like a lot of energy and money is required to get set up initially. In your experience, how would you say the carbon fiber back contributes to the sound of a traditional wood top in comparison to an all wood body?

I've wanted to experiment with CF also, one reason I take interest in this thread. I've cut a lot of CF and Garolite G10/FR4 on my CNC for a previous client. I have endmills that could potentially be able to cut binding channel in CF, but they are extremely expensive PCD tools (polycrystalline diamond).

It is, and that is the nerves and the responsibility talking. If this mold doesnt work out i don`t have bodys, and no way to repay a 10000 Euro loan.

@ Ethanshin

Carbon fiber gives strength and clarity, but lacks warmth. If you make 1 component that has sides and a back, it will be a very strong thing (and improve sustain), but i would still use a wooden soundboard for warmth.

You can factor these cheap bits into the price for your client, if they go dull you just throw it away (or keep using it on wood). Make sure the diameter is compatible with your CNC setup.

http://www.ebay.com/itm/1-4-250-CARB...AAAOSwVL1V~was

http://www.ebay.com/itm/381410198364