Badly deformed archtop mandolin

Discussion in 'Other Guitars, other instruments' started by Hallo Spencer, Feb 28, 2018.

  1. Hallo Spencer

    Hallo Spencer TDPRI Member

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    Hello.

    I've got a cheap Harley Benton mandolin and over the years the top sunk in very badly. The whole thing is even so flexible that you can almost get some whammy bar effects by lightly pressing the top near the bridge.

    I took some pictures. You can see that the top under the bridge on the treble side is depressed by more than half a cm when the mandolin is strung up and tuned. However, the warping is not so bad when theres no pressure from the strings. So I thought I might put a piece of wood between the top and the bottom of the mandolin to stabilize the area but I'm really not sure if that's a good fix.

    I'd really need some advice because the damage keeps getting worse and I'm afraid the mandolin will be unplayable in the near future. Thanks!
     
    Last edited: Feb 28, 2018
  2. Hallo Spencer

    Hallo Spencer TDPRI Member

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  3. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

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    It's possible that there is a top brace that's come unglued, which could be repaired and bring the top back up.
    You might slip a smart phone in the f hole to take pics or even look at the screen, or you can tap on the top and hear the detached brace.
    A violin had a sound post between the treble side of the inside of the top and back, like you're thinking of putting a block.
    That could work too.
     
  4. P Bill

    P Bill Tele-Meister

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    You're on the right track with support from the inside. A violin sound post under each tone bar, at the bridge feet might get you out of the poo for awhile. Only one tone bar in a fiddle and the sound post engages the top directly. The acoustic sound will most likely be very different. I'm guessing here but, like a fiddle sound post, positioning fore or aft will affect the tone. A proper repair would be worth more than the instrument. All the best.

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    Last edited: Feb 28, 2018
  5. philosofriend

    philosofriend Tele-Holic

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    Putting in a post will change the sound, especially the attack of each note. It might sound better through an amp, but don't count on it.

    If you hate the sound of a post, the alternative is to glue a brace on the underside of the top (or reglue the factory brace.) The problem with this is that those F-holes are so small that unless you are experienced at building ships in bottles, you have to remove the top of the instrument to do this! Ugh!

    Violins don't have binding. Taking the top off a violin is almost an easy routine operation. Not so on a mandolin.
     
  6. Paul in Colorado

    Paul in Colorado Telefied Ad Free Member

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    An electric with a pickup like that? Sound post. Is there anyone learning lutherie you know who might be able to do it cheap? A loose brace might be the problem as well, but I've seen '70's Gibson Archtops do the same thing.
     
  7. Hallo Spencer

    Hallo Spencer TDPRI Member

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    Thank you. I hope to snug in the soundpost through the hole for the pickup and not through the f-holes but either way it wont be easy I'm afraid... I know a soundpost will change the sound but when it comes to saving the playability or the original sound of the instrument I'd rather save the playability, right? The sound wasn't considerably amazing in the first place, too. It's really a cheap instrument.
    The loose brace is something I didn't think of and I will definitely have a look inside the mandolin with my smartphone. Reglueing a brace might be even more challenging, though...
     
  8. Solaris moon

    Solaris moon Tele-Meister

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    Um, NO! The sound post has nothing to do with it. BRACING will be a lot more constrictive since it takes up a lot more space inside the instrument. A sound post is only in a small space and doesn't contact much more than about a half inch. The top will still vibrate as usual and not be constrained to having a major alteration. I have a sound post inside my guitar it has trestle bracing from the neck to the tailpiece for rigidity and durability. It keeps the bridge from caving into the body and therefore retains its' natural shape.
     
  9. BGTele

    BGTele Tele-Afflicted

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    Cheap mandolins suffer from top sinkage over time. Hopefully some of the suggestions here will work
    to some degree but I predict the soundest idea will not- a crack will develop similar to a soundest crack on a violin, just a lot of pressure on that one point. The real fix is buy another cheap one or- spend more and get a good mandolin. It will have better resale value and hold together better.
     
  10. jrblue

    jrblue Tele-Afflicted

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    Cheap mandolins with collapsing tops are commonplace because it takes good materials and real skill to build a stable instrument of that type -- 8 strings generate a lot of tension. Often, as others have noted, an interior brace pops loose because the glue job was lousy to begin with, and in that case gluing it back properly can work. If you can get at the brace with glue, fingers, and clamps -- often impossible -- you can do it. Otherwise, there are poor but sometimes possible shortcuts like brushing the glue in place and levering in some dowel posts to create some pressure on the brace-to-top while the glue sets. The real fix is to remove and rebrace the top, an expensive job that is wasted $$$ on a crappy instrument. Yes, you can try making fake soundposts, which might work a bit while they make your mandolin sound even worse.
     
  11. jayyj

    jayyj Tele-Afflicted

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    I think there's a could of points in favour of fitting a soundpost - firstly this is almost certainly a ply top so a lot more resistant to cracks than a solid top, and secondly it need not be a violin style post that puts all the pressure on a very small surface area: rather you can connect the post to the top braces so the upward pressure will be spread along a good portion of the brace. If it were me I'd probaby fit an oblong block wide enough to couple with both top braces and also if at all possible try to reglue the braces themselves so that the post isn't having to support the top on its own, although that might be a challenge if it's not at the end accessible through the pickup rout.
     
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