MINOR JOINT FAILURE QUESTIONS

  • Participant
    gunnar on #205012

    Hello all,

     

    I recently purchased my first harp: a used, 20+ year, 21 string copy of the Holbein bray harp, made by Tim Hobrough in Scotland. It’s in beautiful condition, with new gut strings, save for one small defect: there’s a minor half inch separation at the point where the neck joins the column. This doesn’t go all the way through, the neck is stable, and I know that this joint is actually held in place by a peg, not by two butt ends being glued together. As a harpsichord owner, I also know that certain cracks and separations don’t get worse and don’t affect the sound, and that this might apply to harps as well. I was told by someone knowledgable to insert sheets of paper into the separation periodically to see if it enlarges, and to do nothing if it doesn’t, maybe just fill it with colored wax for cosmetic purposes.

    Here’s a question: if necessary, would a good epoxy keep the separation from enlarging? I know that epoxy binds better with wood/old glue than does new glue. Have any of you stabilized a problem like this with epoxy? I paid a lot (for me) for this bray harp ($575 total) which is still less than if it was new I suspect, but can’t afford a rebuild. Any thoughts? Have attached photos showing the harp, and a closeup of the issue. Thank you!

    • This topic was modified 4 years, 2 months ago by gunnar.
    • This topic was modified 4 years, 2 months ago by gunnar.
    • This topic was modified 4 years, 2 months ago by gunnar.
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    Participant
    charles-nix on #205020

    My opinion: I think whomever you talked to is correct.  Monitor the problem.  I don’t see why you couldn’t fill it with a little colored wax filler on the surface instead of paper.  If the wax then later appreciably separates, you will know it is still moving.  It will move a little with the weather, perhaps, but not much. I suspect that opened up very soon after the string tension stressed the body top and bottom, neck, and column, and hasn’t moved since.  In other words the body gave way a little under the stress and opened that glue joint.

    With a pin in the middle of that joint, the pin plus the glue joint in shear is taking the force.  The glue on end grain (from the neck) won’t hold much, even epoxy.  But the lower, separated part of that joint, which is in tension, is not and never was carrying the main load. What is holding it is the top part in compression acting to push against the top and bottom of the body.  And that is what will cause eventual failure, if it happens: if the body moves further where the column bottom or neck press on it.

    If you put epoxy in it, it won’t hold sufficiently in tension with end grain coated (previously, I would assume) with glue.  You will just make a mess  making it even harder to fix if it does let go eventually.  And epoxy is the devil to get off existing finish if you smear it around any.

    Charles Nix

    Participant
    billooms on #205032

    Gunnar —

    I’m a woodworker (as well as a harpist). My recommendation would be to monitor the size of the separation. The main force from the string tension is in a direction that should not increase the crack and as you say the joint is held by dowels/pegs. I suggest that you do not fill it with wax. The wax would prevent the adhesion of glue in the future should it become necessary to do a repair. Epoxy will not hold well on an end grain joint and as Charles has pointed out it may make a mess. I would simply monitor it over time. I suspect that it will not enlarge any further.

    Participant
    gunnar on #205085

    Hello Charles, hello Bill – thank you for your replies and related information! I’ll leave the harp “as is” then, and monitor it. The wax that I had in mind by the way wasn’t paste wax or polish. I was thinking of colored wax sticks, made with inert ingredients like beeswax, and used by museum furniture restorers. Given their use of reversible repair materials like hide glue, I suspect that it too is removable, but no matter; I can live with the small visual imperfection. Happy to have found this blog and to be able to interact with those more knowledgable than myself.

    Participant
    charles-nix on #205118

    You’re right about the wax, Bill.  Wax would make future repairs more difficult; as would the aliphatic resin that was likely used as the original glue.  We still use hide glue in the pipe organ industry, but almost no one else does.

    What I was assuming (and didn’t say) was that he would use a colored wax stick and only rub it in to the very top surface of the crack.  I should have been more specific; if he runs wax down inside, it would make future repairs harder.

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