Concave Ebony Fingerboard

[Alan Osborne]

Hi All,

This is my first time on the site....

I've just bought an old 1968 Dotras Codobra Classical guitar. It's all solid Spruce/Walnut. The fingerboard is Ebony and is concave/dished in the middle so in other words there is an inwards radius, the gap in the middle is 0.20mm and is pretty uniform over the whole fingerboard. So does anyone know would this have been done intentionally by the maker for some reason or is it the result of shrinkage or some other factor?. All other classical guitars I've seen are either flat or with a very very slight radius the other way.

I intend to re-fret it and would like to know weather to leave it as it is or flatten in out..

Thank you....advice appreciated...

[Mark Pollock]

Hey Alan, welcome!

I'm going to ask a really dumb question, with complete sincerity, since I have been fooled by this before. Have you actually put a straightedge against the fretboard? I've sen several guitar that look like this, but it was an optical illusion, and when I put a straightedge against the board , it turned out to be dead flat.

But yeah, if it is concave , I'd flatten it. That sounds like very little material to remove, so no biggie. Save the dust while you do it, in case you ned to fix a divot somewhere on the board.

[Alan Osborne]

Hi Mark, thanks for the reply

Yes have checked across the fingerboard with a straight edge & feeler gauges. The gap is pretty constant all the way up......Alan

[Tim Mace]

2 possibilities...could be what's called a scalloped FB(intended shape) or xxxtreme professional wrestler grip(unintentional).....thinking you meant Cordoba so it's probably imo inexpensive..if you like the way it plays go/w it or be prepared for a labor intensive attempt to level or replace FB??!!! Any pics??

[Kerry Krishna]

 I have had guitars come through my shop (I am looking at one of them right now) that the fretboard side to side is totally dished, to the point that most of the bottoms of the frets are out of the board in the middle. 

This fretboard was submerged in water.

[Ned Knepp]

I have an old maple ( I think) fingerboard that I replaced because it was cupped like this. it was actually warped "up" on the edges so if you decide to flatten your fingerboard, make sure it's not truly cupped and pulling up on the edges. Look for gaps in between the edged of the fingerboard and the neck. 

You probably won't want to just flatten the board if this is the case unless you remove it completely and flatten both sides which may make it very thin.

[Robbie Collins]

I've run into two concave fretboards - an 1898 Lyon & Healy parlour guitar which I assumed had cupped and, recently, a 2006 Cordoba 25CK ukulele. The uke was nicely made except the bridge was poorly glued and coming off and the fret position markers were all over the place centered.

[Alan Osborne]

Thanks for the information....

[Frank Ford]

We often see fingerboards that started out flat and have become concave. When refretting, I try to correct that issue - in fact, I hardly ever leave a flat fingerboard absolutely flat.  To avoid the potential concave appearance, I always level the board and give it a very slight radius.  

[Alan Osborne]

Thanks for the reply. Yes I have come to the conclusion that the moisture content was to high when it was made,  in fact it had very small splits at the bottom of the fingerboard which point to this.  When I re-fret I will indeed add a radius of maybe 22" or so. I play mostly play steel string and am used to curling my thumb around the neck so the radius would make it much more comfortable. Apart from the fingerboard it's a very nice old (1968) all solid guitar which sounds great so I think well worth the effort..

[Hesh Breakstone]

Hi Alan and welcome to the forum from me too.

You've received some great advice here some of which I will reiterate in detailing my approach.

Is fixing this guitar worth the effort?  Sure if you like the guitar, have the time, inclination, and some of the tools that you will need to have or obtain.

Every concave fretboard that I have seen was never intended to be this way....  It's the ravages of time, RH (relative humidity), and how well seasoned the materials were when this ax was built.  Exposure to flooding can get one here too....  Classical guitars do have fairly flat to flat fretboards though so it seems that this one just wanted to curl up on the edges.

Provided that, as mentioned, the board is not coming loose from the neck and provided that the curl is not drastic enough that once the board is leveled and new fret slots are cut (the originals trued-up and deepened on the edges) without risk of going through the board in the deepening process this is a candidate for a refret.

You will need leveling beams (one would work), self stick sand paper, fretting tools i.e. end nippers, files, crowning files or triangular files, glue to secure the frets, a fret slot saw and tool to clean out the slots, and several or more progressively finer grits of sand paper to get the scratches out of the frets.  A dead-blow hammer (small) or fretting hammer or fret pressing gear and cauls for the fretboard extension.  These things with some determination, patience, assistance from sources that will help you (like us... ;)) and Bob's your uncle!

It might be a good idea too to carefully check out the rest of the guitar especially the neck angle.  I say this because there is no point in attempting a major repair if the rest of the guitar has limiting issues that will not permit it from being properly set-up even when properly fretted.  Neck angle is important, also check for a lifting bridge too, loose braces, and anything else that looks untoward.

Step one is leveling the board which can be done with a precision leveling beam.  Our beams were shop-made out of 1 X 2 aluminum and then they are leveled with bluing with a process that takes several hours on a calibrated surface plate.  Stew-Mac has a beam for sale if you wish to pay the price and the other alternative which can be found on ebay I have no personal experience with.  Regardless the flattening of the beam, even if purchased and not shop-made, is important or you will impart the imperfections of your beam to your frets....

Now this is the tricky part in my mind.  There has to be enough board thickness to have the edges flattened and still have enough depth to reslot the board for the new frets.  You can determine this with your engineer's scale and some careful measuring.  If it comes to pass that there is enough beef in the board to be leveled and reslotted you are good to go.

I use the leveling beam tracing the string paths.  If flat is your goal, no problem.  On steel strings tracing the string path inadvertently results in a compound radius which I personally prefer.

Once the board is leveled you will need to clean-out and deepen the fret slots in preparation for new frets.  A couple of weeks ago someone posted a cool way to do this with a Dremel or there are saws available commercially from Stew-Mac or you can make your own.

Once the board is leveled, the slots are prepared, it's simply a refret at this point and there is a lot available here regarding fretting.

If the board is not thick enough to have the necessary depth after leveling consider replacing the board.  A bigger job for sure which may not be worth doing depending on how enamored you are with this guitar.

Let us know if we can help you and again welcome to the forum. And I almost forgot you will need to remove the old frets (obviously....) too but do so in a manner that does not damage and chip up the board.  If you need help with any of this just ask.

[Robert May]

 and Bob's your uncle!

I really do not need any more nephews !

[Robbie Collins]

BTW, American Lutherie #113 has an article by Mark French called "Making a Truly Flat Sanding Bar."