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Back bow at the nut?


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I've got an issue with the neck on a build I am working on. The neck is back bowed slightly but only towards the nut - the first 1 and 2 frets are sitting lower than the rest of them so I am unable to correct it fully with the truss rod - I did get an improvement but the rod is jacked up pretty tight now and won't go any further.

Any suggestions for the best remedy for this? a couple of things I am considering are: 

1). level the frets down again so frets 3-22 are a little lower than one and 2.
2). pull frets 1 and 2 and see if that reduces the bow at all, maybe the slots are too tight?
3). pull all frets, do a bit more fretboard radiusing to try and reduce the bow in the board, then refret and level

For a bit more detail - I had an issue with a neck I made, the inlays were wrong, so I built a second neck/fretboard. But then I ran into "issues" with the second neck so I steamed the fretboard off the first neck, then I cut the good fretboard off the second neck and stuck it to the first neck. So it seams the issue with the first neck being bowed is probably due to steaming the fretboard from it (I did leave it clamped flat for 2 days which obviously didn't help).

I am trying to avoid building a 3rd neck for this guitar...

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Bummer. I don't have any magic to suggest but, I can tell I've been there. I did the #1 but, while it worked, I felt the frets became too low and then I did the #3. Lot of work but in the end I think it was the right decision in my case. I guess it depends on how much you have to shave off. But if you prepare yourself to do the #3, you might as well try the #2 first.

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Yes I think you are right mate, #1 will leave very little meat on the rest of the frets, I am hoping that I can take enough off the top of the fretboard to get it close enough to level without bringing it too close to the side dots. Then if I have to, take a bit more off the upper frets. 

I am wondering if I would be better off focusing the radiusing sanding on the middle of the fretboard to put a slightly ramp/taper along the length of the board rather than bring the whole thing down to level. I really don't want to go through the inlays or the side dots. 

I have never had a guitar fight me like this one has.

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I wonder what would happen if you steamed the nut end of the fretboard off and glued it back in place making sure it's at least flat or even with a tiny relief. That would require some creative clamping but shouldn't be beyond your skill level.

The trick of steaming and regluing to fix an undesired bow is from Jerry Rosa's bag of tricks.

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22 minutes ago, Bizman62 said:

I wonder what would happen if you steamed the nut end of the fretboard off and glued it back in place making sure it's at least flat or even with a tiny relief. That would require some creative clamping but shouldn't be beyond your skill level.

The trick of steaming and regluing to fix an undesired bow is from Jerry Rosa's bag of tricks.

I want to avoid steam any any costs after the warpage.

I don't have any visible lines where it isn't glued down properly anywhere, so I am not sure that would help. That was the first thing I checked actually, I figured I would have a hump in the middle if it wasn't glued down properly. But there isn't any visible seam showing poor contact, I would see it because both the neck and the fretboard are very light woods. It was a finished and fretted board I was glueing down to mostly carved neck so very difficult to clamp anyway. I hate building necks in that way. 

After thinking it through, I am thinking I will pull the frets and do some selecting work with the radius beam and try to turn the dip at the end into a slight and gradual slope along it's length to achieve relative flatness and achieve the rest with fret levelling if needs be. 

I've unset the neck already so refretting shouldn't be to awkward, although I also hate fretting pre carved necks. 

If I manage to get through this then I will document the build, it's caused me considerable sorrow over the last few weeks. 

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Actually now that I remember it better it was just heat involved.

And it's not about poor contact, it's about stretching one wood and bending the other  like on a curved laminate.

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41 minutes ago, Bizman62 said:

Actually now that I remember it better it was just heat involved.

And it's not about poor contact, it's about stretching one wood and bending the other  like on a curved laminate.

yeah I said steam too, but actually I just meant heat. I removed the problem fretboard with the first neck using a regular iron with the water switched off so there was no steam involved.

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That does things to the fretboard wood IMO, it just made it feel a bit more brittle after heating it up so I pulled the truss rod out of the other neck and bandsawed the good fretboard off. I'd have thought the roasted maple of the neck wood would have faired better under heat treatment though. 

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40 minutes ago, ADFinlayson said:

That does things to the fretboard wood IMO, it just made it feel a bit more brittle after heating it up

Knowing that roasted wood is more brittle than regular dried that doesn't surprise me. Roasting is done in moderate heat to maintain the strength but fretboards are thin so they may get thoroughly roasted pretty quickly. Roasting wood is delicate, it's easy to overdo but if you leave the wood "undercooked" it won't get all the desired properties. For guitar building or furniture making you don't need all the good stuff (like weather resistance) so a light tan may well be good enough in terms of less weight and harder surface. Or just nice looks.

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8 hours ago, Bizman62 said:

Knowing that roasted wood is more brittle than regular dried that doesn't surprise me. Roasting is done in moderate heat to maintain the strength but fretboards are thin so they may get thoroughly roasted pretty quickly. Roasting wood is delicate, it's easy to overdo but if you leave the wood "undercooked" it won't get all the desired properties. For guitar building or furniture making you don't need all the good stuff (like weather resistance) so a light tan may well be good enough in terms of less weight and harder surface. Or just nice looks.

Oh it's brittle alright, the fretboard is pale ebony though, just the neck is roasted maple.

I did my targeted sanding idea after pulling the frets - I made the middle slightly lower to make a much more shallow dip, then sanded down the length to make it an even surface again. It's still got a slight dip between the first fret and the nut but it's flat from the first fret to the 22nd so I think that will do. The dip is only about 0.004" at the nut so I think it will be ok with fret levelling 

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5 hours ago, ADFinlayson said:

Oh it's brittle alright, the fretboard is pale ebony though, just the neck is roasted maple.

And now you've sort of roasted the ebony with your clothes iron. That's what I tried to say.

Targeted sanding sounds like having worked.

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  • 2 months later...

Well this guitar is truly testing my metal. I get it wired up, fretwork done etc and it's one of the best looking tops, one of the best sounding and possibly the best playing guitar I've done. Photographer pops round on Sat to take pics for me and I'm talking logistics with the customer (I need to post it to US).

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I get it out the case to dust it off and the lacquer has checked all over.

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Everywhere there is a screw or pot tightened down, there are cracks emanating from, even the jack plate screws and strap button screws 

So today I got the sander out, started sanding to see if they were just surface cracks from spraying too thick, but these cracks go all the way down to bare wood so clearly the lacquer has not bonded to the wood properly so that tin of lacquer has gone in the bin. 

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I need to finish stripping it completely and do over with some new lacquer for what will hopefully be 3rd time lucky. Approaching 40 builds and none have ever gone as wrong as this one has

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32 minutes ago, Professor Woozle said:

Hope you manage to get it sorted, with the top looking as wonderful as it was before! I think I'd have been experimenting with solvents like xylene to try and get the original finish to uncheck ...

If it was a guitar for me then I might experiment but in this case it's for someone else and the checks went all the way down to bare wood and came from screwing the hardware down therefore I felt the paint wasn't bonded to the wood so I felt stripping it was the best option here.

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