Hi
one of my builds has a slight back bow which I’ve found now that it’s strung up and I am doing the final fretwork
the neck was perfectly straight when I fretted it - so I guess it’s been caused by changing to a different fretwire which must be causing pressure in the slots. I glued the frets too which might also be a factor
Luckily it has a two way truss rod and I can get sufficient relief into the neck.
But it got me thinking it would be a good learning exercise to find out how to fix a back bow properly
I’ve been reading about various methods including heat lamps , clamping , etc
what works best for other people ?
Cheers
Comments
My preference is to level out the back bow. If its minor this can be done on the frets, but more major deformation may require a re-leveling of the board.
even on a straight neck with a single action rod it makes sense to artificially back bow the neck with the rod prior leveling the frets. this gives you some adjustment both ways, you can still tighten the rod more for back bow, or loosen it a bit for a little relief
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so for a very mild back bow ( like this particular neck ) would a good approach be to :
* destring
* slacken the truss rod off to reintroduce the natural back bow
* re-level the frets while the slight back bow is in the neck
* re- crown
* restring and check relief and action
I’m also interested in how to remove the board and introduce a bit of upbow - would be a great exercise if I can do it without spoiling the board. I’ve just been reading about using heat lamps or heat blankets but can’t find any detailed tutorials on that yet.
heat lamps and blankets can work well in the short term, but any heat treated wood will want to return to its original shape.
wood has to get quite warm to reset its shape effectively, so you need to be aware of glue joins and finishes on something as thick as a guitar neck. Also, what's going to hold the neck straight over the following years and all the seasonal changes... hopefully string tension, but if the internal forces of the wood warped it before, what is to stop them doing it again?
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Maybe I should just try re-levelling first and see how that goes. With the rod slackened off now the back bow is back and I could try levelling the whole board in this state.
Worth trying ?
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Out of interest - if I did want to relevel the whole fretboard as you mentioned earlier, how would you go about it ? A case of removing the frets and replacing the board, or removing it and putting upbow into the neck/board glue joint ?
A severe bow may require the board removing and neck shaft levelling, but that is extreme
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I once strung a LP with a very light back-bow up with 13's tuned up to A and left it for about 2 months, once I restrung and tuned to E it was right back where it started!
From what you said in your first post, if you get back bow after fretting then you need to cut the slots wide enough that you don't have that problem.
If you're gluing anyway then you can allow a little more room, but obviously you don't want the slot too big or the fret might not be in the right place.
Crowning and polishing later - fingers crossed it works OK.
It was definitely playable but I'm really fussy about my set up.
really appreciate all the advice.
As wez said you don't want to be in neutral, I also think tension on the rod is better for tone
(formerly customkits)
(formerly customkits)
yes - done some fettling/angling of the back of the slots and polished them with superfine grits and all is now good. Smooth tuning and no sticking.
Also found a very good StewMac video on making and adjusting the nut which is a good resource.
without strings the frets seem perfect when tested with a good quality fret rocker, but once the guitar is strung and tuned to pitch I can find very slight high spots at the 13th, 20th and possibly the last fret.
I’m guessing that under compression the neck is going into a very slight S curve and causing a microscopically convex hump where the neck joins the body.
I wonder if making a fall away would sort this out ?
I did try but not sure if i really did it properly - was winging it a bit tbh
Hoping that one of the experts will put me straight !!
I haven't done levelling under tension, but if you have a way to do it I think it will help
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If I remember correctly , the problem was from 14-15 onwards and so I had to raised action well above I usually like to have .
In the end I did fall away ( first time as well ).
I read that most people use 3 stripes of masking tape on 12th fret for this . Well , I used 4 of them as 3 didn't seem to be high enough .
It is nice and good now again .
Worth a try before you reach for more complicated solutions .