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Glueing help.... (body laminates)

Discussion in 'Luthier's Corner' started by iareplaythebass, May 13, 2004.

  1. Hey,
    I began gluing my body laminates yesterday... on the first one, the joint didn't glue right... I ended up with a gap in the joint about the thickness of a credit card. It wasn't for a lack of clamps or pressure either, I had 24 clamps on it and it's only 16x6". If anybody could give me ideas of what I did wrong, I'd really appreciate it. I'm not hoping to salvage these 2 peices of wood for this bass, i'll use them for a smaller project later.

    Here's some of the little details that might be helpful to know...
    the woods: 1" Mahogany & 1/8" purpleheart
    Titebone I glue
    It was sorta humid when i glued up this joint too if that makes a difference(which I'm sure it does).

    Any tips how I can prevent it when I try again???
    Thanks for your help guys!
  2. schuyler


    Aug 5, 2003
    Atlanta, GA
    humidity will definitely make the glue take longer to cure. on high humidity days here in the southeast US, i prefer to use a polyurethane glue which is actually moisture-curing, so that the more humid it is, the faster the joint cures.

    as for the gap, there are many possibilities why it didn't close up. maybe a piece of sawdust or the like fell in the joint? possibly the clamps came off too soon, and the wood moved? the first question i would ask in finding the problem is "did you clamp the whole works together for a dry run before gluing?" though it takes extra time, a dry run is crucial to getting good seams. any problems with the joint can be found and fixed, and it's easier to tell if the joint is tight if there isn't glue seeping out of it.
  3. Thanks for you thought schuyler,

  4. Without seeing the joint up close (and without my glasses) it's impossible to tell for sure. Here's maybe some other possibilities:

    - a dip in either surface from the planer
    - improperly or incompletely cured (6-8%) components
    - a bubble in the glue film between slabs

    other than that - get out the iron and try to get'em apart :(
  5. schuyler


    Aug 5, 2003
    Atlanta, GA
    if it clamped up dry with no gap, and the gap was there before the clamps came off, this suggests that some piece of foreign matter got in the join while you were assembling the glue-covered surfaces. common problem, especially around my workplace. the only other possibilites that come to mind would be extremely high humidity (raining), which doesn't sound like the case, or a heat source near the wood while the glue set, and that doesn't seem to be the case either. i'll put a dollar on a guess that there's a tiny little shaving of wood in there. good luck getting it apart... a little patience and some gently applied heat and pressure and you'll be back in business.
  6. Yeah i'm betting you're right. It was also very humid, but I'm betting it's some debris in there. I went ahead and bought new wood. I'm just glad it didn't happen with the expensive quilted maple!!!

    Anybody got tips on good ways to make sure clamping pressure is equally distributed when gluing thin peieces such as 1/8"???

    Thanks guys, you've been tons of help :smug:
  7. Suburban


    Jan 15, 2001
    lower mid Sweden
    Sand bag.

    Highly inconveniant to use, because you can't really see any sliding of the joint. Actually, you can barely see anything, except the bag!
    Also, it is not too easy to get the proper pressure = proper bag weight.

    OTOH, it is the only way I know to get an equally distributed pressure over a non-flat surface I know of, less a Quintus press... well. for flat surfaces, too, actually.
  8. JP Basses

    JP Basses

    Mar 22, 2002
    Paris FRANCE
  9. You can eliminate sliding by tape hinging one long edge of the 2 boards. Open up the pair, apply glue, fold up and clamp.
  10. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Owner: FBB Bass Works
    A few things come to mind here.

    1) how long did you leave this clamped up? You should leave them in clamps overnight at least.

    2) Did you use something as clamping cauls? I generally use 1" thick neck cutoffs that run the full length of the piece as cauls to spread the pressure evenly along the surface of the work.

    3) Were the clamps positioned along the edges of the work? Sometimes the edges of the laminate will curl away if the clamps are not right up to the edge. In this case, if you cut into the wood you may find that an inch or a half inch in you have a tight joint.

    4) How heavy did you spread the glue? It's hard to describe the correct amount, but too much can be as bad as not enough. You should get a small amount of squeezout along the entire seam.

    5) How long did it take you to get it in clamps? Titebond has a pretty generous tack time, but ya never know...

    Remember that Titebond has water in it and it can cause the woods involved to move. This is why it's important to spread the pressure evenly, to use the correct amount, and to leave it in clamps for more than the couple of hours it says on the bottle.
  11. Guilty. I left them in clamps about 5 hours.

    I used 2 inch wide 1/4" thick pieces of wood that went the whole length... Maybe some metal blocks would work better? (something very flat and heavy?)

    This very much might have been a problem too... they came to about 1/2" from the edge.

    There was a pretty even sqeezeout, just a few dribbles over the edge in places, and an even line the rest of the way around

    I got them all on in under 2 minutes, so I think i'm in the clear on that one... the dry clamping really does help with that.

    I'm trying again tonight, I'll let you know how this one goes.... :cool:
  12. Skorzen


    Mar 15, 2002
    Springfield MA
    This is where I beleive the issue was. You really need a good solid object to distribute the pressure, especially with a thin laminate. Something like a piece of melanine(3/4" or 1" thick) works well, hard and easy to clean. Sometimes I have been able to "cheat" by clamping the pieces to a flat surface for gluing, with the thinner one the bottom.
  13. Well, I've wasted another 12 bucks worth of wood. Maybe I'll get out the iron and try a few more times before I buy more :( (either that or I'm just gonna screw the whole laminate idea, but how sad would that be... NOT GIVING UP YET!)
  14. Vacuum bags are great for even pressure distribution. 1/4" think is too thin for pressure distribution on its own. Cover your clamping caul with wax paper or saran wrap for easy cleanup.
  15. M_A_T_T


    Mar 4, 2004
    Use a clamping caul like this:


    This is a pic of a fingerboard being glued on a bass I made. The fingerboard is 1/4" thick and being glued to the much thicker neck, but the idea is the same. Use a flat board, a little larger than your pieces, and around 1" thick. Also, use as many clamps as possible.
  16. Do you think a 2x6 would work as a good peice to clamp with? If not, what is? (I'm clamping a 6"x16" 1/8" purpleheart laminate to a 1" peice of mahogany of the same dimensions)

  17. JSPguitars


    Jan 12, 2004
    Grass Valley
    now that's a crapload of clamps, Lex. Better safe than sorry eh?
  18. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Owner: FBB Bass Works
    Are you planning on making the body 1 1/8" thick? Most bass bodies are 1 5/8" thick or so... If you are planning on adding a 1/2" laminate top, you should consider doing the whole thing all at once.

    If the 2x6 is flat and straight, then it would probably work okay. My experience is that they rarely are both flat and straight the way you get 'em. MDF might be a better choice.
  19. the body will be the super hippie sandwich....

    1/4 quilted maple, 1/8 PH, 1" Mahog. 1/8 PH, 1/4 QM
  20. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Owner: FBB Bass Works
    Get well organized ahead of time and glue all 5 laminates at once. That's my advice. Use 2 pieces of 3/4 ply or MDF as cauls. If you're worried about getting everything together before the glue gets tacky, rope a friend into helping. He'll squirt the glue, you'll spread it. Put the first clamps on at the center of the board(s) and add clamps moving outward toward the ends of the sandwich as opposed to working your way to the middle. The point is not to trap any slack in any of the laminates between the clamps as you add them. The layers will slip all over the place so keep an eye on them to be sure that they stay relatively aligned as you slowly add clamps and turn up the clamping pressure.

    Have a layer of wax paper in between the sandwich and the MDF cauls so that the squeezout will not get all over your cauls.