Carbon fiber reinforcement spars.
Do you glue them in the channel? Or do you think a tight fit is good enough? If you use glue, which do you prefer - epoxy, wood glue? Thank you!
I glue mine in the channels with epoxy.
Maximizing the stiffening effect on the neck beam requires bonding. Unglued, there will be less effect.
I glue them in with epoxy. I also glue on my fingerboards with epoxy. ;)
Thank you all.
Epoxy. Cool. Any reason why you prefer it to yellow glue?
David, I was just talking to a luthier the other day and he told me that he has stopped using yellow glue altogether and he's only using epoxy for his builds. He says that he finds it a lot more reliable. Is it the same reason why you use it to glue your fingerboards?
BTW, what kind of epoxy you guys use?
I've used West Systems and System 3 to glue in carbon fibre spars. I don't know that wood glue is going to work well to bond the resin/fibre spars to the wood. Another glue I've seen used for this is CA.
I use CA for my carbon fiber rods and have no trouble with it. It's cleaner and less time consuming than epoxy and the small tubes make it very easy to apply to the channels.
As I understand it yellow glue makes both a physical bond with the wood and a chemical bond as well. With carbon fiber you would lose all the benefits of that chemical bond. Perhaps someone else has a more detailed understanding.
From what I understand, the bonding power of yellow wood glues has to do with the fact that they soak into the surface of the wood a bit, and then when they harden the polymer chains are actually tangled up with the fibers and pores of the woods on either side of the gap, pulling them together. This would explain the difficulty in gluing oily, hard woods like lignum vitae (the wood's minimal porosity is already filled with oils), and why it won't glue nonporous materials such as metal or graphite rods. Epoxy will do the same thing, but is also a structural component itself and has much stronger surface-bonding characteristics on nonporous materials.
I use epoxy for fingerboards because yellow glue has water in it, which often makes the neck bow a bit when you are gluing up the 'board and epoxy creeps less, not that it's ever been a problem. I use Titebond for everything else, but I have glued entire basses together with epoxy (the one in my avatar is an example). It's a very messy process!
I started using epoxy because my partner at SGD was working with Ned Steinberger building the NS Double bass prototypes. They used layers of maple veneer and carbon graphite laminated together with epoxy. We kind of liked that idea, and also I was using phenolic fingerboards with wood laminations. So epoxy was the way to go.
I use G2 epoxy, which is great for oily wood, or West Systems or System 3, which is also very good.
Also used CA with good results
As has already been mentioned, yellow glue will not stick to carbon fiber parts. Epoxy is really the way to go.
CA can work, and I used to put carbon fiber bars in that way.
However, it's got a few downsides:
-Cost - it's much more expensive by volume than epoxy.
-Working time is pretty short
I also think that the CA bonds are more brittle than the epoxies - good epoxy is very strong as a gap filler, and you can use enough of it to really make sure the rod is truly bonded into the neck.
West System 105 resin and 205 hardener is, IMO, the most useful multi-purpose room-temp epoxy for most guitar applications.
Using epoxy for fingerboards has two real advantages - first, there is the moisture issue, which is real...actually, I've started gluing solidbody tops with epoxy for the same reason. With yellow glue, the bodies cup backwards after gluing, and I have to wait about 2 weeks before they straighten out again.
With epoxy, everything stays flat and I can start machining the next day. Big difference!
However, the bigger advantage is in the creep resistance - yellow glues are quite susceptible to creep, especially when subjected to shear stresses, like those in a neck/fingerboard joint. Epoxies will creep much less, despite some mythology to the contrary.
Just keep it off your skin, and out of your mouth, eyes, and lungs, and it can be a really good thing.
I agree. And with CA you need a tight fit. Epoxy is gap filling.
Thank you all. That's very helpful.
David, the luthier I was talking to used the exact same words... It's a very messy process! But it seems worth its while. I live in a very humid climate and gluing necks and fingerboard with epoxy might be a mighty good idea.
Keith, thank you for elaborating on the moisture issue. Again, that is something I should be looking into since over here humidity changes are quite dramatic. I will definitely test it on a top and fingerboard.
Overall, I find myself gradually using more epoxy. For instance I now use it to glue side dots and inlays as opposed to CA. It is messy. But the extra time works for me and the lack of water in it is certainly a bonus.
Availability is always a bit of an issue over here and having an alternative to Titebond is a good thing. Providing I can find those brands or an adequate replacement.
Again, thank you all for sharing your experience.
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