Official Luthiers Forum!

I just had a glue (epoxy) joint fail.
I glued on a fretboard on Monday, and while shaping today, the board came right off. Ugghhhh.
I used Loctite "Extra Time" epoxy. Sets in 60 minutes. (Yeah, sure it does.) Cures in 24 hours. (You bet.)
I guess I've got 3 questions--

1) Bad batch? (I'm not going to contact these people, just wondering if anyone has heard of this before?)

2) Could there have been some adverse chemical reaction? I had a 1/2" strip of Scotch tape running over the truss rod to keep the channel clear of glue. Could that be it?

3) I've got some Z-Poxy here. (Thanks to Paul Woolson.) It says on the bottle "Finishing Resin". Would this work for gluing on a fretboard?

Thanks guys, and any info would be appreciated!

Steve

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Was there any shellac on either surface that were epoxied togather?

Steve, epoxy can be sort of tricky thing.
First and foremost: DO NOT use Zpoxy as a glue. Hypathetically, someone might have used it to glue a bridge once. When this fella turned around to grab his tuner he heard a BANG and turned to see the bridge hanging by all six strings. Of course I have no idea who this guy is because I'd never make a blunder like that.

I doubt there is a bad batch issue. Maybe a mixing issue. I'm not totally familiar with the loctite brand and how it's mixed but some of those syringe types get air in one side or the other so the mix isn't accurate.

Also epoxy can starve a joint very easily. If you clamp and see squeeze out, you'll want to back off on the clamps just slightly. Reason being, the epoxy will keep creaping out for hours until there isn't anything left to hold the joint.

I'd pick some West Systems epoxy and give that a try. It's not cheap. You'll also want to get the pre-measure pumps that go with it. that way it's one pump resin, one pump hardener. No measuring at all. (Otherwise it's something like a 4.9:1 ratio.) Make sure you mix and mix and mix before you spread it. I use a paper plate to mix on. If you do it in a cup it will "go off" on you and get hot, thus setting up very quickly. For some reason it works best to have it flat and spread out as you mix it.

Good luck. Paul

Steve...I use a similar epoxy for adhering FB to the neck. I use a credit card to apply a thin coat to both surfaces and clamp for 24 hrs... BUT I remove the tape over the TR prior to joining the surfaces. I've not had a joint failure yet (n=5).

On the Zpoxy as an adhesive issue. I can't say that it won't work, but I'd want to compare physical properties and joint strength before I'd use the finishing resin as an adheive.

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JJ
Napa, CA
http://www.DonohueGuitars.com

Steve,
I recently had the same thing happen with a lamination using epoxy.
I think it was a shelf life problem-it was open for a while-I did it again with the same brand of fresh epoxy and had no problem.
Was your stuff "old"?

Steve, just don't use epoxy and sounds like everything will be AOK. Sorry for the mishap.

BTW I got in all of my Ambrosia sets from the Auction today. Let me know if you still need one my friend. They are really nice. If I give you a set for free will you build me a guitar out of one, if so I will send you two!

Mike
White Oak, Texas

Steve, I'll repeat what's been said. Every time I have had an issue with epoxy, it has been either (1) the epoxy was in one of those double-sided syringes, and the syringe did not giving me the right proportions, or (2) the epoxy was old.

Another question...sorry, don't mean to hijack the thread. Isn't epoxy designed so it doesn't swell and contract as much with humidity changes? If this is so, wouldn't it make sense to not use it for a fingerboard joint since the ebony and mahogany often used here would likely swell and contract at different rates, and the stable epoxy between them might cause a problem since it isn't moving like the woods on either side?

I must be missing the boat here because many great builders use epoxy. Is the issue above really not a factor?

Cheers!

John

Hey, thanks guys.
Ok, when the board just *pulled* off in my hand, there was plenty of glue in the joint. In fact, it took me a good while to get all that gooey stuff off both surfaces.
Yes, it was one of those double-plunger tubes (which I hate, and am now publically swearing off of!). This stuff was about 3 weeks old. It better have a longer shelf life than that, or it won't work for archival purposes AT ALL. I mixed it very carefully, in fact, I had to keep one side of the tube plugged up, as one part of the mix is so runny, that a straight "plunge" gives an odd ratio.

Paul, I appreciate the annonymous advice from that unfortunate unnamed luthier. I will heed, for sure!

John, the advantage (I think... ) to epoxy here is that it does not introduce water into the neck / board equation. Helps keep things more stable. Trapping water under the ebony is not all that desirable, though I know it's been done since the earth cooled, and man first started putting ebony on his instruments.

Anyway, wish me better luck. And thanks again fellas.

Steve

_________________
From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Steve, from the fact that you refer to it as "gooey stuff" leads me to believe that it didn't get mixed properly. Most likely too much resin and not enough hardener came out of the syringe.

Shelf life shouldn't be much of an issue, however the ratio of part A to part B is a very big deal with epoxies as there is a reaction between the two (duh), meaning that you have to have the right proportions of A & B to get everything to react, unlike polyester resins which are catalytic.
This is also why mixing is such a big deal with epoxies, gotta have all those chemicals in the right spot.Jim_W38945.7975231481

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Jim Watts
http://jameswattsguitars.com

I've used quit a few gallons of epoxy making RC aircraft wings and fuselages. Shelf life generally is not a problem, but improper mixing and low temperature can cause it to not cure. When using the double syringe glues, I hold the syringe with the tip up untill the bubble is at the top. Then eject the air (and sometimes epoxy) untill the bubble is gone. At that point it will meter properly. I like the West Systems products. You can get different hardeners for different ambient temperatures. The slower stuff wil not cure below about 65-70 deg. F . You will find that West Systems is not as picky about perfect ratios as some of the other epoxies. I have successfully used graduated cups for mixing by volume. For gluing you may want to add some thickener.

Al

I agree with Al's suggestion to use a thickener. Unlike most glues, epoxy has no solids to prevent all of it from migrating out of the joint, and into the wood. This is especially true of slow-cure epoxies (like you used, where it has more time to soak into the wood and leave the joint starved.

I use a lot of epoxy in boat building, and I have learned to ALWAYS add thickener when using it as a glue.
You can use either "wood flour" which is very fine sawdust, about the consistency of face powder, or Cab-o-sil, which is silica (glass) also in very fine powdery form. Both of these are sold in any boat-supply store for use with epoxy.

In either case, thicken it to the consistency of ketchup or so.

The absolute strongest joints are made in two steps: first- apply unthickened epoxy to both surfaces, let it soak into the surfaces for a few minutes, and wipe off all that you can. Then, apply some thickened epoxy, and clamp. This way, you get penetration of the epoxy well into the wood surface, and enough thickened epoxy remaining to guard against a starved joint.

Phil

Steve,
I have had good luck using golf club shafting epoxy. It is formulated with a very high shear strength (exactly what we want) and is also reversable with heat. try this stuff - Epoxy

It cleans up easily with mineral spirits. These handy Mixing Cups work well too. If you want to be exact you can weigh part A and part B into the cup on a digital scale to get a precise mix ratio. I have done it both ways with this adhesive and it is very forgiving without weighing it.

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tim...
http://www.mcknightguitars.com

The points that Phil mentioned are very very important. Epoxies (especially
the slow setting ones) can be very prone to yielding starved glue joints if not
properly applied. I've always used West System epoxies, and always use a
two step bonding procedure that Phil spoke of. Wet both surfaces, mix filler
in to the remaining batch and apply that as a bonding layer. Then clamp
enough to hold the pieces firmly together, and no more. Overclamping is a
bad habit that makes starved joints iven more likely when using epoxy.

I know I just basically repeated exactly what Phil just said, but I guess I think
it's important enough that it deserves repeating.

_________________
Eschew obfuscation, espouse elucidation.

Thanks again, guys. I'm pretty sure it was a ratio problem, but I've never had one before. Which is certainly not to say that it can't happen, because apparently it just did. However, this is the first time to use this brand, and maybe it is more particular about exact ratios? And, past adventures have been more forgiving.
Oh, by the way, my shop today had to be in the low 90's, so it wasn't too cool here. (Perhaps too hot? )
And Michael, there was no shellac on either surface.

Oh, and Mike S.-- nice try. Tell you what, I'll build you a guitar, if you build me a lake.

Steve

_________________
From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Steve, we might can work that out, so be careful what you offer I think a nice large pond with some awesome waterfalls and a nice long stream could be on the horizon. I will also add a complete backyard landscape plan so you can have that "Paradise" nestled in the Piney Woods of East Texas to play those awesome guitars you build. I will give this some serious thought. Maybe a winter project while things are slower with the cash and carry folks. I like bartering

Mike
White Oak, Texas

Now, wow, what an offer!!! isn't this place great or what?

Steve, don't trust the plungers. If you want to be sure of your ratio, measure in grams and then you'll be assured that your mix is accurate. I use West System epoxy on my fingerboards and never had a failure. Yes, it takes overnight to cure but I glue on the fingerboards at the end of the day or during the day and carve the next.

Can I ask a dumb newbie question that no one has mentioned? Why are you using epoxy to glue on a fingerboard? I thought that was a job for Titebond I, LMI white, or hide glue (to make disassembly easier, if necessary.)

I'm not wagging a finger, I am just asking.

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Dennis,

Some folks use epoxy for the fingerboards because it doesn't introduce water into the neck, which can sometimes cause a warp. People have also found out that epoxy is reversible with heat, just like the other glues.

Ah, the thread has resurfaced!
Dennis, your question is fair. And in fact, all those glues you mentioned will work fine. The purpose--as I understanded it--was to keep from introducing water into the neck / fingerboard joint. All those other glues you mentioned are water-based. But, again, they have been used successfully.
I don't know if Rick Turner was the first to start using epoxy, but he was one of the first at least. His rationale was as stated above. I believe the LMI catalogue states that a potential problem with a water-based glue in the neck would be back bow. Or perhaps some other kind of warpage.
Anyways, that made sense to me back when, and I've been using epoxy since then. For this joint only. AND, by the way, it does come apart with heat. I gladly learned that by fortunate experience.

Steve

_________________
From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Well, Carlton, we were typing at the same time.

Only you were more concise!

Well done, you!   

Steve

_________________
From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

I have used 5-minute double-plunger epoxy to glue two fingerboards together edge-on for the 10-strings I build. I haven't had a joint fail yet. Usually I used Devcon -- haven't tried Loctite, but I wouldn't be averse to using it. Now I use the 1:1 System 3 (5 minute) that you can buy at places like Woodcraft and Rockler. Again, I haven't had a joint fail using this stuff either. Main reason why I switched to the Sys3 was partially out of convenience, and partially because it is more economical in the long run than the double-plunger stuff you can buy at hardware stores.

As others here have mentioned, proportions are critical. And based on Steve's later comments, it appears the proportion was off.

What I do with the double-plunger epoxy is the same a person does with any sort of syringe: you waste a bit of the product to get the bubbles out. Once the bubbles are gone, I run a bead onto wax paper, mix it thoroughly and then apply it post haste. And even though it says 5 minutes, it doesn't really cure hard for at least 8 hours. Since I have to thickness sand the fingerboards after epoxying them together, I usually wait a day before I thickness them.

I'm curious, though -- why not just use Titebond to glue the fb down to the neck? Is moisture the big concern? I use a miniature paint roller that's used for painting in corners and tight spots -- you can get them at most any hardware store for a couple of bucks. I apply the Titebond to the neck surface sparingly and roll it out with the roller until I have a thin, even coating. Almost no squeeze-out. And more importantly, no excessive moisture being trapped between the fingerboard and the neck blank. Also, the roller is reusable. Let it soak in water for a couple of hours and rinse all the old glue out, and it's good to go again.

Best,

Michael

_________________
Live to Play, Play to Live

I, too, use Titebond for most joints. The 'trick', if you can call it that, to avoiding moisture problems is to leave parts in the clamps until they're _dry_. Moisture can't really get 'trapped' in wood, but it can take a while to work it's way out of a dense wood like ebony. Leaving the parts clamped and imobilized for 24 hours usually does it.

I tend to use as iittle epoxy as I can get away with. I had one student who became quite allergic to the stuff, and have heard some real horror stories. The only places I use it are where the lack of shrinkage and somewhat higher mechanical strength will tell, such as side- to end-grain joints and in putting in truss rods. That comes to about two places on the average guitar.