Glue Joint Fail

Discussion in 'Guitar Building' started by bmac6502, Apr 22, 2016.

  1. bmac6502

    bmac6502 Member

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    Hmm. What to do.

    [​IMG]

    This happened after staining. The stain is water based, so I'm guessing the moisture caused some swelling, but also the split is pretty clean at the joint line, without much splintering, which means the glue didn't bond well there.

    The question now...what to do about it?
     
  2. Michael_P

    Michael_P Member

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    The failure is rather interesting...looks to me like the woods moved (or were perhaps forced together...e.g. not a good joint in the first place) and caused the failure...in theory a good glue joint would be stronger than the wood which also indicates a starved glue up...as far as to what to do now I think the only choice is to cut that wing off and reglue it...the only option as far as saving what you have would be to get a lot of glue down in there (using compressed air with an adjustable air blower like the Milton S-115) and try clamping it together, which will be difficult as the shape is already defined...
     
  3. HEADKNOCKER

    HEADKNOCKER Active Member

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    I agree, If you want to try an just get some glue in there clamping might be a problem unless you have the scraps that you cut the wings from, Those should make a perfect clamping caul...
    Otherwise just get a small kerf hand saw & cut it loose & plane + reglue..

    Good LucK!!
     
  4. bmac6502

    bmac6502 Member

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    Hmm interesting. I do have all the scraps that came off this guitar, so I might be able to make a caul. The neck is a carved heel, so the maple is blended into the mahogany at the neck and I'm not confident I could saw it off and reglue it without it being off by an unfortunate amount. Also, the pickup and bridge cavities/holes are partially into the maple portions, so I'd be concerned about disrupting pickup/bridge mounting unless I got a REALLY thin kerf saw (I don't have one that thin).

    I suspect, given the shape of the body and the availability of caul pieces, that I might be able to clamp it down. I guess to start I will try to set up the clamps and cauls, and see if I am able to apply enough pressure to close the gap. Is the consensus here that *if* I can dry clamp the gap closed, then a proper amount of glue should hold it?

    If that fails, what about gluing a wedge of mahogany into the gap? As I said, I saved EVERY scrap. I have had good luck matching up the mahogany for plugging goofs in the other guitar which was made from the other half of the mahogany block. That was my "practice" guitar, so that this guitar, my real objective, was not my first time doing the more delicate operations. That practice guitar involved several goofs which had to be patched (I drilled through the back while trying to drill holes for the pickup wires, for example), and I found the grain pattern on this block of mahogany to be highly forgiving. The grain is very uniform, tight and straight, so if I cut a wedge that came from a nearby region of the block, it would probably blend well, especially for such a thin strip running parallel to the grain.
     
  5. Michael_P

    Michael_P Member

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    making a proper wedge to bridge the issue would be the trick if you can pull it off with alacrity...as I noted that failure is weird and since I don't know how well the pieces mated up before glue up I can really make no comment on the setch...perhaps the woods were still a bit green and hadn't had time to properly acclimate to their surroundings...either way, clamping it back together is just forcing bent wood into place and could very well result in a new glue joint holding and the wood failing...

    making a wedge

    still tricky...

    remember this...if you do go the route of removing the wing and making the pieces true, you will simply be removing more wood to recarve the heel and route for the pickups...it's easy to remove more wood, rather difficult to add wood!
     
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  6. HEADKNOCKER

    HEADKNOCKER Active Member

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    After thinking about this for a while I too think the best way to fix it "RIGHT" would be to cut the wing off plane both pieces on a shooting board & re glue & then taper the defect out by sanding shaping & reroute the pickup cavities..
    It's really the only way to do it correctly, as stated above squeezing it back together will more than likely get you right back to where you are now..

    Good Luck!!
     
  7. bmac6502

    bmac6502 Member

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    After taking a closer look at it, and experimenting with clamping - I agree with the idea that squeezing it back and re-gluing will simply cause the wood to fail instead.

    My concern with cutting the wing off and regluing, is that I am a beginner working with a limited shop. I had a lot of trouble with cutting and shaping that maple with the tools I have at my disposal. That's probably got something to do with why the joint failed, and unless I have access to some tools that could work that maple more effectively, attempting to re-joint that maple is probably just going to result in more of the same problems. Maybe it would be ok, but my instinct is telling me that if I attempt to remove and reshape that wing, I'm as likely to butcher it as I am to rescue it. If that's what it comes to, so be it, but I'd like to exhaust other options first.

    I experimented yesterday with making a mahogany wedge and feel like there is potential there. I can't imagine there's any harm in taking a shot at filling the gap with a wedge - if I fail, as you guys said, I'm going to end up sawing the wing off anyway.
     
  8. Michael_P

    Michael_P Member

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    limited tools...yeah...

    what I'd do is cut the wing off with as little material loss as possible...then using a VERY straight piece of material as a 'pattern' use a top bearing router bit riding along the straight edge to route the pieces straight....not sure of your contours on the back and this might present problems in clamping the 'pattern' in place...you also have the 'problem' of the longest top bearing router bit made is a 1/2" shank and 1.75" long...

    when I do such as I describe above I make the pattern out of 1/2" baltic birch and make it fairly wide and long to make sure the router is fully supported...I clamp it in place using Irwin XP quick grip clamps and go to work...you have to be very careful and focused...one tip of the router and you've fudged it all...for best results take off very little material at a time and climb cut with the router (which is pulling it towards you)...yeah, this is tricky, but pretty much eliminates issues with the wood blowing apart...what happens is that since you are in 'reverse' the bit is compressing the wood as opposed to pushing it away from itself.

    Good Luck!
     
  9. bmac6502

    bmac6502 Member

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    Well I had time to play with the wedge this afternoon, and...Wedged!

    [​IMG]

    I wasn't quite able to get the wedge to drive into the hairline part of the split (wood that thin is just too flimsy to drive itself into that split). So I had to do a small bit of wood dust/glue slurry just to fill in the gap cosmetically, but I think it will be of only minor consequence with the color on. The color is going to be tinted urethane so no worry about being unable to dye the glue fill. If I were a professional building this guitar for a customer I definitely wouldn't call it acceptable but since this is build #1, and it's for myself, I'll take the little bit of "character", given the relative ease of the fix.

    Now the only question is, will it hold? The wedge is thin enough that if the wood wants to keep on moving it may not hold. I'm going to keep it under observation for a while before resuming the finish. If the wood wants to keep on moving, I'll have no choice but to cut the wing off and try to rescue or remake it.
     
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  10. poro78

    poro78 Well-Known Member

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    "Cutting the wing off" sounds bad... Do you mean literally or by softening the glue and removing it "kindly"?
     
  11. bmac6502

    bmac6502 Member

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    Yeah, it would probably mean "cutting". I'm not sure how good an idea it is to try and release the glue with heat - the wing joints come within an 1/8" of the fretboard. I'd be worried about releasing the fretboard glue.
     
  12. Zeegler

    Zeegler Active Member

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    The wedge might solve the problem cosmetically, but since the glue joint failed at that spot, I would assume that the rest of the joint isn't ideal either.

    I actually had a similar problem once. I had a much smaller gap than you have there, but I strongly suspected the entire joint was glue starved, and thought the best solution was to get the wing off and re-glue properly. However, instead of cutting the wing off, managed to get the wing off by using gentle pressure with the body clamped to the workbench with a spacer board under the neck portion and using a clamp to slowly increase pressure on the wing until it gave way. I realize I was taking a chance that one or both of the two sides would split or splinter at the joint, but it came apart very cleanly. I simply cleaned up both sides of the joint with a plane and re-glued using plenty of glue this time. Problem solved.
     
  13. bmac6502

    bmac6502 Member

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    Part of the problem I have is no jointer. I set up my router table with an offset fence to substitute as a jointer, but in attempting to joint those particular edges it kept wanting to snipe. I thought I had managed to get the kinks worked out, but if anything was wrong with that joint, it is likely a hairline amount of snipe that meant wood contact was weak at that end of the joint. I clamped the guitar to the edge of my workbench and leaned on that wing pretty hard, I don't think it's going anywhere.

    Unfortunately, I completely failed at hand planing that maple, I just couldn't get it to cut, even with a freshly sharpened blade. I don't know what was up with that piece of maple, but it was HARD. Way harder than other maple I've dealt with. No matter what, the plane either just wanted to bite in or tear out curls.

    So without investing in tools (which I have no budget left for), I might get that wing off, but that doesn't mean I could joint it any better this time around. I suspect that without a proper jointer I'm as likely to ruin the piece as improve it. I'd say the fact that you were able to remove the piece fairly cleanly without a saw or heat means you didn't have nearly enough glue, and re-gluing was probably the ideal fix. In my case, since the rest of the wing seems strongly glued, the failure is probably more due to poor wood contact.

    Question for the hand tools guys - have you guys ever encountered wood (esp. hard stuff like maple) that was TOO hard? i.e. you just couldn't work it with hand tools at all? I'm curious about my failure to hand plane that maple. Would there actually be better quality hand tools that might have handled it? Is there trick or technique that I might be missing out on? Or is there a real possibility that a piece of maple could just be too hard to hand work?
     
  14. poro78

    poro78 Well-Known Member

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    Sounds like planing against the direction of grain.
    Curly maple, wengé, purpleheart - I had difficulties with them all, until I found out that I was planing with plane iron extended too much or planing the wrong way.
    The most difficult one was the current build's 5-piece laminate neck, where I accidentally put the middle piece of wengé the wrong way.
    Now the other pieces have grain running towards the body and the middle piece's grain runs towards the headstock.
    So I got some tearing in the middle when planing towards the body end or some tearing in the sides when planing the other way.
    The answer to that problem was toothed plane iron, which is helpful with difficult grain.
    But if you don't have one, you just have to be bit more careful in adjusting the plane iron and reading the grain.
    (Cap iron as close to the cutting edge, etc. Really thin shavings, blablabla...)

    Here's the thing I'm trying to explain with my limited English vocabulary:
    [ame]http://www.youtube.com/watch?v=14i_gaLw_5I[/ame]
     
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  15. HEADKNOCKER

    HEADKNOCKER Active Member

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    I've seen some folks joint boards by putting sandpaper on their bench & running the board across it back & forth till no light can be seen when held up to the sun or bulb..
    A plane gets the wood way smoother than sandpaper, A scraper could also be used if the boards are close to where you want them..

    I have a homemade router table & have an adjustable fence system & have tried to plane some boards as you suggested & it can work to some extent..
    Myself when jointing boards I always end up going back old school to the plane..

    Bedrock No 602
    [​IMG]
    Bailey No 6
    [​IMG]
     
  16. bmac6502

    bmac6502 Member

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    This is what I mean by a "limited" tools collection: I have only one plane, an old Stanley #4 smoothing plane. That's it. All my jointing was done with either that plane, sanding blocks, or the router.

    Actually, now I have two planes. My grandfather passed recently, and left me a block plane owned by my great-great-grandfather. It's got to be a late 1800's plane. It most certainly is not in working order, and I am not sure about the prospects for restoring it, but also, as an heirloom, I don't know if the plane is better honored by being kept as a memento, or being restored and used.

    I did try reversing the planing direction to see if the maple was happier going the other way. Didn't seem to help much. The toothed plane sounds like it might have been the thing I was lacking.

    I don't have a planer either. I had to dimension stock with a table saw and band saw, then clean up with the plane and sanding blocks. The results were often imperfect. I think I managed to get ok results in the end, other than obviously this one issue, but it certainly made things a lot harder than they needed to be. I definitely will not attempt another guitar until I have the tools to true up stock more effectively.

    I have some home improvement projects coming up next that will require milling larger lumber, so I am hoping I can make a planer and/or hand planes part of the budget for those projects, since they will otherwise require me to get somebody else to do some milling for me.
     
  17. poro78

    poro78 Well-Known Member

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    #4 was enough for my first build...
     
  18. bmac6502

    bmac6502 Member

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    Well, what I had was enough, *except* when dealing with those maple wings. Even the baked curly birdseye for the fretboard was manageable. That's why I was so thrown by it - it was ONLY that one stock of maple that was a problem with hand working - even other maple was a relative breeze.

    That's why I wasn't sure if it was tools, technique, or the stock itself. I was fairly new to hand planing, so I wasn't above suspecting my tools or technique, but the fact that it went so well with all the other stock made me quite confused...
     
  19. poro78

    poro78 Well-Known Member

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    Maybe it's the piece of maple then...
     
  20. HEADKNOCKER

    HEADKNOCKER Active Member

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    Probably the grain of the piece of wood you used to make the wings from
     

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