Having obtained a messed-up seven-dollar guitar to work on, I decided to expand my repair skills. The fretboard had been pried off from the nut to about the fifth fret (I have no idea why; the guitar at present has no bridge or nut, and the tuners are trashed). I removed the fretboard, frets intact, without difficulty (I have a TERRIFIC method for heating fretboards for removal, which I'll share with y'all if you're nice :) ). So now I'm looking at a bare bolt-on neck, without fingerboard. With no pressure on the truss rod, the neck shows a significant backbend/convex relief. A straight-edge lined up at mid-neck shows about 2 mm of daylight on either end.
The truss rod doesn't appear broken or damaged, and I know string tension will have a serious effect, but what I would like to know is what the standard pre-fingerboard relief should be under these conditions. Should I sand the neck dead flat before regluing the fretboard? Is that backbend "normal"?
"You can't write a chord ugly enough to say what you want to say sometimes, so you have to rely on a giraffe filled with whipped cream." - Frank Zappa
good Q. flat would seem the answer ... or the 'obvious' answer, but the problem with that is if the environment changes, you could find yourself dealing with an uncorrectable backbow (negative relief). and with a maple + f-board neck, that might even be stiff enough to stay backbowed under light gauge string tensions => problem. so if I were doing this, I consider one or more of these:
* glue up with a slight to moderate relief (forward bow). this will guaranty some available relief if necessary (sometimes it is), plus give the truss rod "something to do" so it's not rattling around in the cavity.
* change the truss rod to a two way. that would guaranty full positive and negative relief adjustment range.
* slot the neck on either side of the truss rod and add some stiffening inserts, then build with a slight relief. these also will help resist twisting.
good luck -- let us know what you do.
-=tension & release=-
........................but what I would like to know is what the standard pre-fingerboard relief should be under these conditions.........................Is that backbend "normal"?
The answer to that is a definite maybe. It all depends on the current atmospheric conditions, compared to "normal" conditions. I take it that the fretboard is not maple, like the neck, itself. Different woods will react differently to changes in temperature and humidity, which may account for the current back-bow.
........................Should I sand the neck dead flat before regluing the fretboard?........................
I would say "no". Better to get the neck straight(er) by doing what gnease has said, although I would go for gluing the neck up to be dead straight (but under "optimum" climatic conditions). If the guitar is currently held in cold, damp conditions (in a normally unheated work-room, for example), when you take it into a warm house or when summer comes around, the neck is going to change quite significantly and, maybe, not for the best.
I started with nothing - and I've still got most of it left.
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Gnease & Greybeard, thanks for your help!
It all depends on the current atmospheric conditions, compared to "normal" conditions.
I'm in Colorado Springs, where it's drier than my previous experience of "normal." In the house we run consistently at 40-50 percent humidity.
I take it that the fretboard is not maple, like the neck, itself.
Board appears to be rosewood, between 3/8 and 1/4 inch thick. Neck is solid wood, one piece, too grainy and dark to be maple. (It's a Japanese bolt-neck Les Paul copy, likely a Cortez, with single-coil pickups under the "humbucking" covers and an inlaid butterfly on the headstock.)
...I would go for gluing the neck up to be dead straight (but under "optimum" climatic conditions).
Check. Since I'm working with a fretted fingerboard (of reasonably good quality), I suppose my first steps with this neck should be to remove stray bits of wood & glue from gluing surfaces, then clamp board to neck & check the fret plane with the straightedge. I'll have to do all that anyway, and it will certainly give me more info about what to expect from the neck overall, no?
What I'm gleaning here is that a backbow under the fingerboard is not necessarily a structural flaw in itself, if the final build (i.e. fingerboard/fret plane after glue-up) has correct relief. That is, the maple/mahogany/whatever under the fretboard, if backbowed, "should" not impart convex relief to the fingerboard/fret plane if the final build gives me a slight concave relief on the playing surface.
(Yes, I know that "should" is a terrible word, esp. with a 40-year-old neck of uncertain history My concern is that I don't thin the neck so much by flattening under the fingerboard that I build in new structural flaws.)
* * * * * * *
Here's my fretboard-removal tip: Around our house we have lots of hot packs/cold packs for athletic/age-related injuries. They are homemade -- small fabric "pillowcases" filled with dry rice, corn, grains or beans, then sewn up tight. Put one in the freezer, and its holds the cold wonderfully for a couple hours. Microwave it for five-six minutes, and you have two hours of moist heat. I heated up a rice bag, draped a damp cloth over the fretboard, & applied the bag for 15-20 minutes -- and with a little coaxing from a kitchen knife, the board peeled right off. Didn't even damage the binding along the fretboard. Much easier to control than a steam iron, and way lots cheaper than the pro-style heating blankets.
"You can't write a chord ugly enough to say what you want to say sometimes, so you have to rely on a giraffe filled with whipped cream." - Frank Zappa
What I'm gleaning here is that a backbow under the fingerboard is not necessarily a structural flaw in itself, if the final build (i.e. fingerboard/fret plane after glue-up) has correct relief. That is, the maple/mahogany/whatever under the fretboard, if backbowed, "should" not impart convex relief to the fingerboard/fret plane if the final build gives me a slight concave relief on the playing surface.
right -- it's the final relief that matters more that the curvatures of the unglued/unassembled parts. a high amount of stress built into the neck is probably not desirable, as it may cause more environmentally-influenced variations. but some built-in stress is okay: so it is fine to clamp a slightly warped or curved neck and/or fingerboard into the desired shape (to achieve zero or slight relief (concave)) when the glue is set.
-=tension & release=-
...it's the final relief that matters more that the curvatures of the unglued/unassembled parts.
Got it. Thanks!
a high amount of stress built into the neck is probably not desirable, as it may cause more environmentally-influenced variations. but some built-in stress is okay: so it is fine to clamp a slightly warped or curved neck and/or fingerboard into the desired shape (to achieve zero or slight relief (concave)) when the glue is set.
It follows then that on a brand-new neck you would want the neck plane under the fingerboard to be as flat as possible, so the stressors on the final build are limited to ones you can control (string tension, truss rod). (I very much want to build myself a strat-style neck before I die....)
"You can't write a chord ugly enough to say what you want to say sometimes, so you have to rely on a giraffe filled with whipped cream." - Frank Zappa
