Suggestions on fixing a fingerboard extension on adjustable neck?

[Randolph Rhett]

I recently built a guitar using an adjustable neck along the lines of the Doolin setup in GAL. The lower heel is bolted in at the bottom and the upper heel rests against two adjustable posts. The two posts push out or retract to raise/lower the action as well as align the neck along the centerline of the body. Groovy.

The result is a neck extension that by necessity is not glued down. Unfortunately, over time this extension is starting to warp up. No doubt a twist in the blank I didn't see originally. I have tried to use a heating blanket and pressure to bend the extension back down, but it continues to want to curl up. We are taking 1/16" at the most, but it is more than enough to cause buzzing.

In this case, the extension is just the ebony and floats a tiny amount over the soundboard. I know Taylor supports the extension and cuts away to top to accommodate it. Not really sure how I would retrofit the existing setup to do this.

I am not sure what else to do. If I glue the extension to the soundboard the neck will no longer be adjustable. Somehow I'm in a brain freeze about this and can't seem to figure out a solution.

Suggestions?

Thanks.

[Mark Swanson]

this problem has nothing to do with the body, so don't mess with that part. Don't consider gluing the fingerboard dowwn, or cutting into the body or any such thing- this lies with the neck. So, remove the neck to deal with it. You might have to use heat to flatten the extension, heat it and clamp it.
The two pins at the top bolt are not for adjusting the action, but to provide a pivot point and to align the neck. Turning the bottom bolt will make the neck angle change from there.

[Clay Schaeffer]

You could add a couple of position markers at the 17th fret that would hide a pair of flat head machine screws that could be bolted through the top. If you elongate the slots through the top you could still have adjustment, although as Mark mentioned, the "tilt" adjustment should be with the lower fastener to avoid changing the scale length.

[Michael Lewis]

This situation is easier to prevent than to remedy. Some sturdy carbon fiber strips inlaid into the underside of the fingerboard should do it. That is what Rick Turner is using on his adjustable neck design. The reinforcement must extend at least an inch over the neck, and to near the end of the fingerboard.

[Doug Shaker]

The fretboard wants to bend up and the underside is invisible to the player. Graphite cloth is pretty strong in tension. I wonder if you could remove the neck, clamp it straight, then epoxy a strip of graphite cloth on the back side under the part that wants to curve up. Then the tendency to curl up would have to fight the tensile strength of the graphite.

[Jason Rodgers]

This situation is easier to prevent than to remedy. Some sturdy carbon fiber strips inlaid into the underside of the fingerboard should do it. That is what Rick Turner is using on his adjustable neck design. The reinforcement must extend at least an inch over the neck, and to near the end of the fingerboard.

Yes, and the CF is 1/2-1/2 or 1/3-2/3 in the fingerboard and neck. Mike Doolin did this with CF tubes. I think Mark has done this, too, right? Of course, this doesn't help you now, Randolph, unless you wanted to pull the fingerboard and retrofit such reinforcements.

[Mark Swanson]

Yes, I run CF tubes down the length of the neck, to the end of the fingerboard.

[Bob Hammond]

Hmm, I wonder if a few fret-slot-width kerfs on the underside of the extension, along with some heat to flatten it would provide enough relief. It might be possible to fill in the edges with a bit of dark-colored wax to make them virtually invisible. Or it might be possible to stop the kerfs before the edge if a dremel was used with a slotting saw blade. As always, test on scrap first.

[Randolph Rhett]

I have two CF rods down the length of the fingerboard, but I just didn't think to extend them out into the extension. Live and learn. This is what I did on the next guitar I made, but I like the one I am now having a problem with.

I can steam/clamp it flat, but with time it wants to cup again.

DOUG-- you give me hope. I had hoped not to have to remove the fingerboard. I can always try epoxying a small sheet and see if that counter-acts the cupping. It is worth a try, at least. If not, I can always pull the fingerboard and put a new one on. I hate to waste good ebony (not to mention the work).

MICHAEL -- I have never used thin rigid "strips", but the big G lead me to a hobby shop with 2mm thick by 3mm wide carbon fiber rods. Is that what you are referring to? Is that strong enough to resist the cupping of the fingerboards and keeping them flat? Do you know the dimensions of the material Rick Turner uses?

Thanks all. I'll probably end up pulling the fingerboard and using the "strips", if I've understood Michaels suggestion. Not 100% sure about the CF material in question. Perhaps someone can steer me in the right direction there.

I'll post back in the Spring to let you all know if the solution worked.

[Jason Rodgers]

I think 1/8"x1/2" or 1/8"x3/8" CF bars are what some folks use.

[Mark Swanson]

I have used both 1/4" round and 1/4" square CF tubing. I don't like my neck to be quite as stiff as it would get if you used those deeper bars. It's possible to make the neck so stiff that even the trussrod will not move it, at least not much and the 1/4" tubes give me all that I need.
Plus, the tubes are hollow, and this allows me to run fiberoptic cables up the tubes and out of the position dots in the side of the fingerboard so I can make all the dots light up with one led. I don't always do that, but it's an option.

[Michael Lewis]

Randolph, whatever you use has to fit in the space you have, so that limits your choice. I'm not sure what Rick uses but you can ask him, he is a helpful fellow. I think the 2mm X 3mm stick would do pretty well. 3 or 4 pieces inlaid on the under side of the fingerboard before you glue it back on the neck should suffice. I would run them just short of the end of the fingerboard and over the neck by at least an inch. If that doesn't remedy the issue you have a very rebellious piece of ebony.

[Steven Smith]

I have the same neck joint but had a different problem (truss rod popped through the neck). I pulled and replaced the fret board. If you do that then you can put the CF rods in under the extension as noted in the original AG article. That's the way I reinforced mine and they work fine for keeping the extension flat. I did have to cut slots in top for relief for the rods but that was no problem

[Trevor Gore]

Can't you just compression fret the extension? How many frets of extension are there? (And if they're on unsupported extension, don't they sound "dead"?) Or am I imagining this wrong?

[Jeff Highland]

Could you drill into the end of the neck under the fretboard to epoxy in whatever reinforcement you use to support the extension?