Preferred bowed neck repair method

[Drew Streip]

I have a Washburn mandola that is, in most regards, a good instrument. Unfortunately, all attempts to correct the excessive forward bow with a truss rod have failed, leaving me with uncomfortably high action.

Most of the bow seems to occur around the first few frets. But the neck itself seems sturdy -- it even has a volute like a violin neck.

I've read about heating the neck; I've read about planing the fretboard; I've read about removing the fretboard and planing the neck itself; and I've read about compression fretting.

Which of these is the correct solution for a fairly unplayed instrument? I also get the feeling that it sat in a warehouse (or multiple warehouses) for a while before I got it -- possibly strung to pitch with overly heavy strings, as it was when I bought it (at a discount).

PS I strongly dislike the tiny frets, so regardless of my repair options, a voluntary refret is in my future.

[pops1]

If a refret is in the future I would start with larger tang frets. You may also loosen the fretboard from the nut just ways back, if most of the bow is there, simply clamp the neck so it is straighter and reglue. If it is hide glue this would work well, if not taking the board all the way off to clean glue would be necessary. Between the two you may correct it without planing. If you can correct it without removing wood and making the neck weaker that would be my preference. Since it sounds like you are doing it yourself should that fail the board can be taken off and the neck planed, but I have had success just regluing without planing.

[rowka]

Rosa String Works has a YouTube video showing a fretboard removal that revealed a poorly executed scarf joint where the scarf was proud on the rest of the neck. Considering the location of your defect, this might be your situation.

[EdHanrahan]

... Most of the bow seems to occur around the first few frets.

We're assuming you mean frets 1 thru 3 or so, not the "first few frets" near the body. In my experience, it's more common to have such "concentrated" bow happen at the neck-to-body joint.

OTOH, are you sure it's not too-high nut slots, or maybe a partial re-fret (most often on 1-3) w/ frets that were not dressed down to the height of the older ones? I've had both of those happen.

[rcc56]

Is this a modern Washburn or a pre-war instrument?

I don't mind planing a board on an instrument with a mild to moderate bow IF the neck seems strong and stiff. I have not had much success with attempting to straighten a board by compression fretting only. I view compression fretting mostly as a technique for stiffening a neck, rather than relying on it as a neck straightening technique.

For severely bowed necks, "heat pressing" does not hold for the long term.

As Pops said, on a hide glue instrument, the glue joint can be opened up from the nut through the bowed area and reglued with a caul that pushes it into a back bow of maybe .020" or .030". This should be followed by a plane and compression re-fret.

If the bow is VERY severe, or if it is a modern instrument assembled with Titebond or PVA, it is better to remove the board completely, scrape off the old glue, and either plane the neck true or clamp the neck into a slight back bow [possibly heating the neck carefully before you clamp], then re-assemble as above with hide glue. Each job must be evaluated individually. On some instruments, it may make more sense to plane the neck itself rather than trying to re-shape it.

For necks that are inherently weak, the neck should be reinforced.

Most off the shelf mandola string sets are too heavy for pre-war mandolas. I recommend buying singles and making your own sets. For a pre-war Gibson, I have had good results with 12-20w-32. For the fourth string I will use anywhere from a 48 to a 52, depending on the individual instrument. Old flat-top mandolas may need to be strung somewhat lighter.

[Folkmusician.com]

Can you get us some images? Preferable with a straight edge (or use the strings)?

[EdHanrahan]

Whoops! Didn't mean to cut myself short. Should have finished the thought with...

... too-high nut slots, or maybe a partial re-fret ...? I've had both of those happen.

"... and both cases initially struck me as excessive bowing near the nut."