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Hello Folks, I tried the method of brading with carbon fiber described in the Gore/Gilet book. Gluing the bracing was a bumpy road and I may have messed it up but Im not sure exactly how serious it is. I just took a video of the issue. Check it out and let me know what you think. -Alex http://www.youtube.com/watch?v=rvRvODpk ... e=youtu.be

I'm not much help but I did want to bump this up so those that might can see it.

But.... in general terms I would say you have two options. You named them both.

I would test how well the brace is attached to the top with a little prying with a chisel. If it is good and tight then I would go with the option of putting a little more epoxy under it. If it is easily loosened then removing and starting over would be my chose.

But then again I do not know of what I speak.

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Joe Beaver
Maker of Sawdust

What would your concern be with filling the space? Do you feel it would create a structural issue or a tonal issue?

Well, quite a few issues here.

First, this is not a design I cover in the book. I do CF with a lattice (classical) and CF with falcate for SS. I mention that because the size of the braces in this X-braced design is an issue, I think, in this case.

I don't know what the brace height actually is, but it looks a lot bigger than ~7mm I use for falcate bracing. What seems to have happened is that the brace is so stiff because of its height that it hasn't been properly pressed into the dish by the go-bars. The CF itself is very unlikely to put up sufficient resistance to keep the brace off the panel unless the epoxy was already hardening. The finger braces where the CF has squeezed out show what can happen if the gap is closed with too much resin in there. So I think lack of initial dry fit is the root cause. What you want to see is closed gaps, no escaping CF and a small meniscus of epoxy at the base of the brace as per the picture below.

So, what to do about it? I don't think you have sufficient width of glueline if you can slide a piece of paper in ~3/16" each side (~5mm - how wide are those braces? ), or even just on one side. I'd be inclined to remove the brace (chisel it off) and re-do it. I'm also concerned about the epoxy. Is it designed as a coating or an adhesive? The 300/21 mix does not appear on Aeromarine's list of epoxy adhesives. The harder epoxies tend to be weak and brittle and whilst they might work fine as potting compounds (for example) they're exactly what you don't need as an adhesive and is why I recommend WEST, which I used successfully on boats a long time before I started using it for guitars. So it might be worth a quick test to see how well things are actually stuck together. If it sticks well and is reasonably shock resistant you could consider running epoxy into the gaps. The right epoxies have good cohesive strength so should work. It depends on who you're making the guitar for, I guess.

Another word of general warning - don't get hooked into the hype that glues have to be really hard to work. Just about any of the glues commonly recommended for guitar making set a lot harder than the wood if used properly.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au