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Messed up scarf joint?

Discussion in 'Luthier's Corner' started by Easy Rider, Mar 20, 2006.


  1. I glued up the scarf joint today on my neck project, but I have serious doubts that it's going to work out...

    Because as I left this afternoon it showed quite a seam along the edges located on the sides of the blank, even though it's clamped like a mother. The wood (1 piece wenge) was very dry, so I'm guessing it was too dry and now the Titebond is retracting?
    But even then, there shouldn't be a seam, right? The joint surfaces are flat and true, so I'm a bit boggled. :confused:
    I did wipe off the excess glue enthusiastically, should I have left more of it so it could be 'pulled back' into the seam as the moisture in the glue is being absorbed?

    But anyway, if everything does appear to have turned to crap tomorrow morning... the glue being Titebond I, can the joint be steamed off like a fretboard?
    If it needs to be done, I could just spare the length of resawing it, but I'd rather not.

    Any help or advice is much aprreciated!

    Heck, don't think I'll be getting much sleep tonight... :scowl:
     
  2. Rodent

    Rodent Supporting Member Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Regenerate Guitar Works
    can you post an image?
     
  3. Alas Rodent, I cannot. I forgot to bring the danged camera today...

    I'll try to explain the situation better with some ASCII-art depicting a cross-section of the seam:

    -wood--|
    --------'
    ]]]]]]
    -------¬
    -wood--|
    --------|

    This is what the glue (]]]) seems to be doing, retracting into the seam, which I guestimate to be 0.5 mm wide...
    Now the retracting I attribute to the dryness of the wood, but why is there such a seam? Is it the thickness of the glue that has to 'come down' as the moisture is absorbed or is something terribly wrong?
    Like I said, the surfaces are really flat and it's clamped evenly with four clamps... it's all supposed to be textbook... :eyebrow:
     
  4. andvari7

    andvari7

    Aug 28, 2004
    Ennui
    I might have a suggestion that might not mean anything (but it seems logical to me):

    Alembic and Carl Thompson sometimes (read: almost all of the basses of theirs I've seen) use a headstock veneer on the back of the stock (at the joint). Though I'm almost completely positive that its primary function is aesthetic in nature, I see the possibility of increased structural integrity.
     
  5. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Maryland
    Owner: FBB Bass Works
    I don't think that the problem is the Titebond pulling back or the wood being too dry. You should be able to seperate the seam with heat.
     
  6. rdhbass

    rdhbass

    Jun 28, 2003
    Springfield, mo
    This is why i always dry-fit all my parts before i finally glue them, and this goes along with the cut once measure twice rule. A person should never be in a hurry to obtain better perfection.
     
  7. Suburban

    Suburban

    Jan 15, 2001
    lower mid Sweden
    This is not at all my area of expertise, but I have some ideas. Not on what happened (except that you may have been overenthusiastic in removing the excess) but on what to do.

    You have glued up the blank, right? That means that you have a lot of wood to remove until it is a neck.
    So, the potential area of problem would be the fingerboard side. Possibly the back. Planing/sanding away 1 mm on each side will not be a problem.
    The sides will be cut away when you taper the neck.

    NOTE: not my area of expertise, I may (however unlikely:rolleyes: ;) ) be WRONG!
     
  8. Suburban makes a good point. Another thing about joints, if not prepared well enough, can sometimes also show a seam when sanded back, which reveal that the surfaces have not mated close enough. Hopefully, if that happens, enough glue was applied to cover the hairline gap.
     
  9. Well, it didn't turn out quite so hot. One side I find very nice, too bad I can't copy/paste it to the other side...
    Let me show you...
    ...and the nails are in pre-drilled holes btw, used only for positioning!!

    The nice side!
    [​IMG]

    The crap side!
    [​IMG]

    Guess I still rushed it too much :meh: or maybe the nail used for positioning started to bind during clamping...

    I'm going to try to see how deep the seam is (with a needle or something) because if it's not that deep then indeed the part that's left after tapering will be structurally quite ok (not perfect) and I'll keep it as it is, keeping the ugly seam as a reminder to cut once and measure thrice...

    Are there pills against the 'I feel like a dork' syndrome?
    Oh no wait... hmmmm, beer...

    Good thing it's not the wood being too dry, I heard that makes the joint utterly unreliable and to be done over, more so than it is now... Well, I don't think it'll fail that easily, I take good care of my instruments and use very light string gauges. Plus there'll be a 5mm thick macassar ebony fingerboard on top of all this.

    Many thanks for the responses! (Further responses are still welcome ofcourse)
     
  10. Basschair

    Basschair .............. Staff Member Supporting Member

    Feb 5, 2004
    Stockton, Ca
    How wide is the neck blank?

    If it's wide enough, you could always plane away excess from the offending side, cutting away at the section of wood that didn't glue up properly. This is similar to the idea that this part may come out in the tapering/shaping process, but instead of taking off material equally from both sides, you could focus mainly on right side. Afterwards, build up the headstock by gluing wenge strips to the sides (depending on how wide a headstock you need).
     
  11. The blank is 80mm wide.
    My headstock design is 75mm wide and asymmetrical, with the left side being 35mm wide and the right 40mm, so I can shift the neck centerline 5mm to the left, which I will most definitely do now, thanks :)

    Building up the headstock is indeed an option, good point.
    But I hope that won't be necessary, it looks a lot better as a single piece and the ugly joint will already be quite the blemish by itself.
    It's supposed to be a 3-piece bass (not counting the scarf joint): neck, fingerboard, body (yes, it's a 1-piece body, honduras mahogany) so I hope that'll still work out.
     
  12. Basschair

    Basschair .............. Staff Member Supporting Member

    Feb 5, 2004
    Stockton, Ca

    Cool: I hope it works out!
     
  13. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Maryland
    Owner: FBB Bass Works
    Just drive those nails in all the way. Problem solved.

    I would probably try to figure out how deep the bad side of the joint goes. Plane off a mm or so and see what happens.
     
  14. +1!
    If it goes in quite a bit don't think "I'll put up with" coz you won't be saying that when your strings pull it clean off! bass strings pull 180-200 pounds upwards :eek: , that join has got to be bang on!
    steam it off plane it again, check it with a stright edge up, down and corner to corner as it might of had a bump in the middle which might of caused it to "rock" pulling one side up (was the good side the first side you clamped?), don't put up with second best, it could well come apart which will be a nightmare if the whole bass is finished :crying: , and it'll bug you every time you pick it up!
    do it right, you wont regret it :bassist:
     
  15. Yeah I agree, if it goes in too deep I can't trust that joint. At first glance it doesn't look like just a mm deep :meh:
    So then I'll be steaming away...

    But if it filled out ok it'll leave an ugly, thick seam but which should be structurally sound. Titebond has quite the shear strength.

    Well, didn't have time to work on the neck today, so tomorrow will be judgment day.
     
  16. good luck, I hope it turns out fine!
     
  17. Finally had time today to inspect the joint, so I took of a mm or two, and look what I found:

    [​IMG]

    Sah-weet! Very much relieved to see that. If it weren't for the jump in the grain the untrained eye couldn't tell it's there.
    So, the work can continue as (sort of) planned.

    Ahh... the beer sure tastes better now. :)

    Thanks everyone!
     
  18. Basschair

    Basschair .............. Staff Member Supporting Member

    Feb 5, 2004
    Stockton, Ca
    Congratulations!
     
  19. nice! that's realy good news. bet that feels better now that problem is out the way.
    looks sweet, keep us updated on how the build goes.
     
  20. might of been a bit of roll off, where you come to egde with the plane (or even more so the sandpaper) and very slghtly round the edge over.