Twisted Neck Humps

[DC Ross]

I built a neck & attached the fretboard after making certain everything was flat & true. I then shaped the neck & fretted (again, after verifying everything was good to go). I came back to it today after a couple of weeks, and went to level the frets when I noticed that the neck has twisted a bit & there are a couple of humps in it around the 5th & 12th frets, so it's kind of wavy. It's not like it's a pretzel, but it is noticable and I don't think leveling will be enough to take care of it. Are there any other options than pulling the frets, re-leveling the board, then refretting?

thx,

-dc

[erikbojerik]

A few things come to mind:

The lumber was not completely dry...?

You unclamped too soon...?

You didn't register to a flat clamping caul when gluing down the board...?

You've had some big temperature & humidity swings since gluing the board to the neck...?

The fretboard was flat on one side only, and had variable thickness....?

Before doing anything....get yo bad self a good straightedge, and use it often....check & recheck every step in the neck-making procedure.

If it were just humps in the fretboard, I'd yank the frets and re-level. But with a twisty neck....nah it's not worth fighting it, remove the board if its a good one, keep the truss rod and toss the neck blank into the firewood pile. Start over with good dry lumber, and make sure you have either quartersawn or flatsawn grain....no rift-sawn!

Also, a 3-piece laminated neck blank should be more stable than a 1-piece blank.

Good luck!

[fryovanni]

+1 to what Erik has said.

Add STRAIGHT GRAIN, in either well quartered or Flat orienation would be best.

Out of curiosity was the neck straight grained and basically quarter or flat sawn?

I was looking through a stack of soundboards I recently dried. Now normally I have no issues with soundboards cupping or twisting at all. However, I did have three pieces that were cut from a bolt that had a bit of the shadow from a knot. This creates a cupping in the face grain, even though the board is dead nuts on quarter and extreamly close to perfectly straight grain and clear as can be. These three pieces dipped right around the shadow (enough that the boards are worthless). Sometimes these things have little effect on the wood, sometimes it is quite severe, but there was no doubt as to the source of the deflection.

Peace,Rich

[Woodenspoke]

I built a neck & attached the fretboard after making certain everything was flat & true. I then shaped the neck & fretted (again, after verifying everything was good to go). I came back to it today after a couple of weeks, and went to level the frets when I noticed that the neck has twisted a bit & there are a couple of humps in it around the 5th & 12th frets, so it's kind of wavy. It's not like it's a pretzel, but it is noticable and I don't think leveling will be enough to take care of it. Are there any other options than pulling the frets, re-leveling the board, then refretting?

thx,

-dc

You have no other options.

I agree you rushed the project and used wood that was not ready or for some reason your shop had a complete 180 deg swing in conditions or poor wood selection Blah Blah Blah.

I think you need to put the neck down wait a few months and see where the wood settles since it may not be over just yet.

[DC Ross]

Thanks for the replies, guys. I used some kiln-dried Maple that I've had for a couple of years. It's flat sawn & I thought it had stabilized enough when I started. I have a couple other guitars (> 20 years old) that also have flat-sawn Maple necks that haven't had any issues, so I figured "why not?"

I built this particular neck last September, so I think it's settled as much as it's going to.

At any rate, I'll definitely take the advice & pull the frets then see where we're at. Hopefully I'll be able to give the fretboard a good leveling & all will be peachy

[Prostheta]

As far as I understand, internal tensions can exist in wood which balance out over the drying period and move a little seasonally, but are released and changed when you alter the shape of the piece which causes a new settlement period.

Anyone care to elaborate on this further, as I may well be mistaken and may be using my plausibility gland. I think I read something about this on PG, but I can't remember for the life of me where.

[joshvegas]

my humps, my humps, my lovely neck lumps?!

Makes sense to me prostheta but I but my doctor says i have an overactive plausibility gland!

basically you cut through fibres and if they are under tension when the timber is straight and square you're going to get a shift of some sort the right choice in wood grain it will make it negligible that's my view i'm sure someone more knowledgable will correct me!

[fryovanni]

As far as tension. When a bit of wood dries it shrinks in various directions, but in different amounts (Longtitudinal very little, Radial more, and tangential usually twice as much or more * Ratios vary however radial and tangential shrinkage is always significantly higher than longtitudinal). Sometimes enough stress is created to crack the wood, sometimes it is enough to move the wood, there is also a chance you will have differing stresses that balance out enough(although they are not linear throughout) to allow it to stay in place. If you remove a bit of wood during carving that had higher stored stress than the wood around it, that could lead to a bit of movement. It should not be a huge amount of movement generally, depending on exacly how large the piece was, and how much wood is removed, how much imbalance was present. Since straight grained clear wood shrinks in a reasonably predictable manner the chances of getting much movement would be reduced by using wood that meets that criteria.

It sounds like he has used wood that had plenty of time to stabalize, and become aclimated to his shop. Flat sawn wood is not a problem. When glueing it is possible that swelling from moisture in the glue used, uneven clamping, possibly not clamping until the glue has set could become possible issues(as Erik mentioned). We are not sure how much distortion has occured(I assume it is fairly small).

It would be interesting to hear more about the time lines(how much time was given between steps), type of glue used, cauls and clamping methods and so forth. Hard to say for sure if there is something he could have done differently to prevent this from happening. It sounds like he used good judgment in selecting the wood and stabalizing it. At this point it would seem like allowing enough time for the wood to settle down as much as possible, and then fix the issue would seem reasonable. If it moves too much, I would not use the neck. We build these things to last for decades not a few years, and it would really suck to have a problematic neck down the road.

Rich

[SwedishLuthier]

I would strap the guitar up in a neck jig, do all the measures, pull the frets and plane the fret board under simulated string tension. I have had necks in with perfectly straight grain behaving odd and uneven under string pull. Twisting like mad. Only way to deal with that is to sand the fretboard dead flat under tension, then refret it and level the frets under tension too. Adding the internal stress from the frets can make the neck move again. You would be surprised to see how much and how odd a neck can move under stress.

But as mentioned we do not know how much the neck have warped. A pick or a few measurements would help