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This is the first time I've encountered this issue. Hoping someone can offer advice.

I'm working on a couple of necks (new builds). I've been working on getting the fretboard straightened out on the one. Unfortunately, the raw stock wants to bend. It's Mahogany. African, which I don't typically use but it's what I could get my hands on. It's basically back-bowing. I noticed it during the glue up. I figured, if anything, it would probably work to my advantage by counteracting string pull.

What is happening is I'm having to sand so much off of the board that the middle is getting a little on the thin side. It's almost completely straight except for the very last few frets. With a straight edge down the centerline, I'm able to get a .013" or .014" feeler gauge under it at the 21st-22nd fret area. I thought about using a heating blanket to reglue the fretboard with some relief. Neither of them are carved yet either. I'm wondering if they're just going to undo all of my leveling work once I remove all of that material from the back.

What do you all think? I'm not so concerned about the visual aspect of the FB being too thin in the middle since the necks will have bindings. The other one is doing the same thing. In case I went about the first one the wrong way, I'm thinking maybe I can salvage the second one.

Thanks!

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

What species is the fingerboard? Any curvature to the grain of either the neck or fingerboard? Any curly figure? Are you sure it's all good and dry and acclimated? My humidity has recently dropped 10%, so it would be a bad time to glue and level fingerboards here.

The fingerboard is EI Rosewood. I really think the neck is the culprit here. The piece I used is basically quartersawn. The grain is straight up and down. However, the piece it was cut from is approaching the center of the tree. I'm thinking the grain is wanting to bend toward the center of the growth rings as it naturally would. I heated up the 2nd neck and reclamped it with some folded up paper over the center of the truss rod equaling roughly .025". I guess we'll see what that does.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

I bought it from a lumberyard that sells kiln dried wood. I would assume it's stable but perhaps that's no all there is to it? No curly figure, just straight up mahogany. It's been pretty cold here. For Atlanta, anyway. It's been in the 30's and 40's. Is that too cold for glue-ups?

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

I just removed the fretboard from the 2nd neck. It's completely unusable. I've never seen a piece of wood bow like that. I had it flat within a couple thousandths of an inch prior to routing the truss rod channel. After removing the board, even without measuring it, I can visually see a gap of around 3/32" - 1/8" on either side of the straight edge. I'm blown away.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

You got that right. All I want to know now is why. Does it mean that it wasn't dry? Are there ways to visually evaluate grain that I'm not aware of? Is African Mahogany more prone to warpage?

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

Yup, sounds like it. Shame, but at least it sounds like you don't have much work in them yet.

Some grain issues can't be seen. Nothing like watching it turn into a pretzel to confirm what's stable and what's not

Ideally, you should keep a decent stock of neck wood and check them with a straight edge a couple times throughout the year to see which ones curve and which ones stay perfectly flat. Curvies get chopped up into heel blocks for the straight ones, or linings, or furniture.

I have one Indian rosewood blank that looks curvy, yet seems to be quite stable. I keep debating whether to use it or not.

What is the structure of the neck? Is it basically 3/4" stock with a built-up heel? If wood is improperly cut and dried, it can become "case-hardened"- ie, it has high stresses built into the wood just below the surface, and when that wood is cut away, the imbalance of stresses from front to back causes a bow. I don't know if that is your problem, but it's a possibility. If you haven't done any machining on the back of these necks, I'd try removing some material to see if the bend goes down ( You'd be removing the stressed fibers on the opposite side of the neck). I'd also talk to the wood supplier and see if he's willing to make up any of your loss. If it's not a built- up neck, then the wood was probably cut from a stressed tree, and not relieved because the boards were cut thick.

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Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

Kinda... I had truss rods installed, headstock veneers trimmed. After leveling the boards, it was time to carve. But you're right, at least they weren't set to their bodies yet.

I've been reading up on African Mahogany. Apparently, it's a little tricky to find a good piece. Had no idea.

Screw it... I'm just gonna pony up the extra cash and build a couple new ones with Honduran.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

They were cut from a piece of 12/4. Heels were not built up. Necks are all one piece. I didn't carve them but I guess at this point, it couldn't hurt to try it.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

burn it! burn it!

Huh... Huh.... FIRE!!!

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

Khaya (African Mahogany) can warp. That's the answer. buy some marshmallows and enjoy the warmth of the fire.

Yeah, I agree with the above- if they were cut from 12/4 there were some big internal
stresses built into the wood. You could try rough carving one to see what happens, but
I doubt it'll be very successful. Too bad about all the wasted effort, though...

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Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

I wonder if it was dried too quickly. I've been told that can happen. It would make sense with this particular piece since it warped toward the center of the annual rings. It may have just been wet in the middle.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

uhm...yeah...in my experience Khaya is a very unstable wood prone to doing God knows what when material is removed from stock...I rather hate it...note this statement is made in a statistical sense...it can be a very good wood when you find a piece that has the right stuff...

I did some reading about it. Apparently there are 3 different genus of "African Mahogany" and it depends on what kind if soil it grows in. Certain areas have a higher silca content in the soil. Others have the wrong amount of exposure to sunlight. I was picking up some Honduran mahogany this morning and the supplier is very knowledgeable. He pointed out that, more times than not, the lumber coming from Africa these days is pretty unstable in general. Not just the Mahogany.

Of course this is all what I heard. Not claiming it to be fact.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."