# Instruments and Equipment > Builders and Repair >  What fretboard radius is most common?

## Charlie Ayers

I'm trying to decide how much radius I want on the fretboard of an F5 I'm having built. Is the standard 12? 

Thanks,
Charlie

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## Flowerpot

I can't speak for everybody, but 12 is sort of flat. I'd say that 9 inches is more common, and 7.5 is not that extreme.

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## Magnus Geijer

I'm obviously no great fount of knowledge, but I'd say 12" was the most common.

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## Tom C

I had a flat. When I got my new mandolin, I got it with a 12". This is a slight radius and feels very comfortable.

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## John Flynn

Just a few data points:

Rigel's compound radius is 9.5" at the nut, flattening out to 16" at the end of the fretboard.

Weber offers 10" and 8.5" as options.

Stewmac sells pre-radiused boards for builders that are 12."

Of course, what is a "significant" radius is a personal perspective. Also, I think the width and thickness of a neck and the size of the fretwire play a role in whether a given player will percieve a given radius as being significant or not.

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## sunburst

I build mandolins with a 7 1/4 inch radius fingerboard. Some people don't even notice that there is a radius when they play it.
The width of the board makse a lot of difference. On a guitar, 16" is noticable, (Martin) 12" and 10" are common, (Gibson) 7 1/4" is used (Fender).
To me, 16" feels flat on a narrow board like a mandolin, so 10" or less seems better to me.

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## Charlie Ayers

Thanks for the input, everyone. I hadn't been able to find much on builders' websites, but I hadn't checked Weber or Rigel. I may go for 10".

Charlie

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## Brian Ray

I have a 12" and it is still quite flat but makes all the difference to me. I'll be looking for at least a 10" next time but possibly 9".

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## Chris Baird

The compound radius is the way to go. I like a flat bridge and I think nearly everyone I've talked to does as well. Of course a flat bridge on a non-compound radiused fretboard gets hard to fret on the outside strings. A radius of 9" at the nut and 18" at the end is what I like.

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## Willieee

I was recently looking into this issue also. #I e-mailed Rigel, Collings, and Breedlove, with these replies:

Rigel: 

Compound radius that runs from 9 3/4" at the nut to 15 
3/4" at the fingerboard extension. The bridge saddle has an approximate radius of 18".

Collings:

Compound radius. The nut is 4.97339, 12th fret is 8.90
(I asked about the size at the bridge saddle and they did not respond.)

Breedlove:

The radius of the fingerboard is 12" down the whole neck. #The nut width is 1-3/16". #The scale length is 13-15/16" #


I spoke to someone here in Seattle about the issue of compound-or-not-compound, and he stated that the reason for a compound radius is that it prevents the string from "fretting out" when one bends the string. #He said that the compound radius was developed for electric guitars, and you'll find a compound radius on Strats, Teles, etc., for this reason. His opinion was that a compound radius was not needed on a mando when one plays mostly bluegrass and therefore does not bend the strings much. #

I would be interested in folks' comments about this opinion on compound radiuses (radii?).

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## Chris Baird

As I already stated the main plus for compound radius is that one can have a flat (18") bridge with a radiused fretboard. You get the best of fretting and the best of strumming and picking. Obviously we as mandolinist don't have to worry about problems with big bends but as was stated above a compound radius solves that problem as well.

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## John Flynn

I have also heard the "electric guitar/string bending" rationale for a compound radius and it makes sense. I am no expert on this, but I think there is another reason to do it on a mando. As someone mentioned on another thread, the wider the fretboard, the less radius you need to have the player feel it is "significant." So a 16" radius on an electric guitar is a decent radius, but on a mando, it feels nearly flat. A compound radius would put more radius where the fretboard is narrower, closer to the nut, and less where the fretboard is wider, up the neck. It should result in a more consistent feel up the neck. Also, the string bending thing does apply to some mando players for some styles of music. All I know for sure is that I really like the compound radius on my Rigel. I have also always liked playing Collings mandolins in stores, more so than other brands, and I didn't realize until your post that their radius was a compound. 

Another observation I would add to the discussion is that I think string tension plays a role. I have three mandos, the Rigel and two with flat boards. All have had full set ups. I am OK playing the flat boards as long as I have low tension strings on them, but when I get up to heavy strings, I need my compound radius. Just my $.02.

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## Ed Goist

I've been researching the possibility of putting a compound radius fretboard on a future custom build and I came across this thread. Very interesting stuff.

It seems that many of the builders who offer a radius fretboard today use the simple 12" radius (maybe using a pre-jigged board?). However, the reasoning above regarding the multiple benefits of a compound radius on a mandolin seems quite strong. (The old "best of both worlds" [fretting & strumming] argument).

So for those (players and builders) who like a radius on the fretboard, what is your preference?:

* 12" fixed
* 10" fixed
* 9" fixed
* Compound radius: 9.5" to 16" with 18" saddle
* something else

Oh, and one more question, can the Collings' compound radius board really have a radius of 5" at the nut?! That's almost violin like, isn't it?

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## Ed Goist

> ...snip...
> Also, I think the width and thickness of a neck and the size of the fretwire play a role in whether a given player will percieve a given radius as being significant or not.





> I build mandolins with a 7 1/4 inch radius fingerboard. Some people don't even notice that there is a radius when they play it.
> The width of the board makse a lot of difference. ...snip...


To reinforce these comments, take a look at the graphics below. On a narrow board (say 1 1/8") it's very hard to visually tell the difference between the 12" and the 9.5" radius:

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## robert.najlis

cool graphic!

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## Charles E.

Ed, nice graphic. I am about to profile my fingerboard and the compound radius seems to make sense. I have noticed on old mandolins that originaly had flat profile fingerboards, that after awhile they had become cupped. I would like to avoid that.

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## Ed Goist

Tons of really good information about fingerboards, including the above and several other printable Radius graphics (ranging from 6" to 20") on this wikipedia site.

Plus, pretty good stuff from Stew-Mac here,

Also, I was somewhat surprised to see that Stew-Mac sells pre-cut compound radius boards for mandolins. From the site: _"... 7-1/4" at the nut, to 10" at the 12th fret, to 12" at the 29th fret, to allow lower string action and easier playability. 13" bridge saddle radius is recommended..."_

Charley, I see your point. Also, if a radiused board is desired, it would seem that compound would be the clear choice. It doesn't seem like anyone would need/want the more severe arch down on the fretboard that the 'straight radiused boards' have. Am I missing something?

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## amowry

Wow, this thread is a blast from the past. I like compound radii, though when we're talking about mandolin fretboards, the difference between all these radii is pretty minor, as Ed's pointed out. I find I quickly adapt to pretty anything from a flat board to a relatively pronounced radius without noticing much difference, but that may be just me.

In theory, though, I agree that a compound board makes the most sense. As an aside, when the frets are filed on a board with a cylindrical radius (the same radius the whole length), the shape of the surface of the frets comes to approximate a cone (i.e. compound radius) anyway. That's because the frets are leveled parallel to each string, and the strings converge towards the nut.

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## Phil Goodson

My 2 favorite mandos both have compound radius boards, going from 7.5 at nut to 17 at end of fingerboard.   I could probably stand even a little more radius at the nut.   I heard that John Reischman's mandos have 5.5" radius at the nut.

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## Rick Cadger

Some great info and links there, Ed. Thanks for sharing.  :Smile:

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## Jesse Harmon

Great thread.  I just liked the Rigel the minute I picked it up.  I think if I was an experienced mando player I would quickly adjust to anything as I do on the guitar but being completely new to the mandolin neck and fretboard  the difference just jumped out to me right away from my American Conservatory.  Great graphics.  I think when you look the difference is quite visual.  No question I would use compound radius on a build if I get that far.

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## sunburst

Here are some of my thoughts on fingerboard radii;

First of all, I like arched fingerboards, I think they feel better and most people (but certainly not all) prefer them, so I put arched fingerboards on nearly every instrument that I make. In the case of a typical arched fingerboard the arch is a section of a cylinder, and the radius of the cylinder is the radius of the arch. When people say "compound radius", they are referring to an arch that is a section of a cone, so starting now in this post I'll refer to that as a conical arch as opposed to a cylindrical arch.

The strings of most instruments are narrower at the nut and wider at the bridge, so they diverge from one another as they go from nut to bridge and describe a portion of a very narrow V. When you stretch a string level over a flat surface at any angle the height is the same from end to end. If you stretch a string level over the surface of a cylinder the height is the same from end to end only if it is stretched parallel to the center line of the cylinder. If it is stretched diagonally to the center line it will be slightly higher at each end and slightly lower in the center, so if we stretch a set of mandolin strings level with the surface of a cylinder the V of the strings will make the outer strings run slightly diagonal to the center line of the cylinder and they will be slightly lower in the center (actually, all the strings are slightly diagonal). We can gather from this that a flat 'board is better than a cylindrical 'board because the strings are parallel to the surface… but mandolin strings are not level with the surface; they are almost always higher at the bridge than at the nut, and we almost always put a little bit of relief in the fingerboard to avoid string buzzes, so in practice, the fingerboard relief in a cylindrical 'board is slightly flatter under the outside strings than under the center strings. How much? hard to say, but not much. It could be figured out mathematically, but my guess would be .001" or so. If we accept that fingerboard relief in a mandolin fingerboard should be…say…4 to 6 thousandths, we can have relief in that range under every string even with cylindrical fingerboard.

What if we can't accept a thousandth or so variation in fingerboard relief and we don't want a flat fingerboard? We must use a conical fingerboard. For a conical 'board to improve the situation, the cylinder must be of a shape that allows each string to follow a path parallel to the center line of the cone, so it must match the V of the strings exactly. The shape could be figured out mathematically with the starting points being the arc of the strings at the nut and at the bridge. Those curves would determine the shape of the cone from which the fingerboard shape is taken. Now, it is up to the luthier to be able to measure and accurately make the fingerboard to that shape. How? By hand and by eye? Can we get closer than the .001" or so error introduced by the use of a cylindrical 'board working by hand and by eye all the way through to finishing the frets? I suspect we hardly can, and that we tend to introduce more errors in a 'board like that then in a cylindrical board where we can measure the arch accurately end to end. Add to all this the fact that most necks are wood, and wood is often somewhat inconsistent in density and stiffness so neck relief is often not perfectly precise even before humidity starts things moving in the instrument, and you can start to see why I use a cylindrical fingerboard. I feel confident in my ability to make the cylindrical radius accurate from one end of the fiberboard to the other, whereas I feel that even if I can figure out exactly what cone shape would work with the V of the strings I'm left with establishing the shape by eye so I have less confidence in my ability to "get it right" working with a cone.
I do re-frets on mandolins with conical fingerboards from time to time and they turn out fine even though I'm basically just accepting that it was correct from the start, but I think we are splitting hairs when we say that a "compound" radius is  "better" than a simple radius because of all the reasons listed above. Further, after a few fret jobs and bridge replacements all bets are off…

Hopefully this rather rambling account makes sense to those with the patience to read it, and explains why I think a simple radius is usually just as good as a "compound" radius. One other thing that I didn't mention; some people say they like the feel of the strings more nearly level at the bridge and that is the reason they prefer a conical fingerboard arch. That's fine, and is a good reason for using a conical 'board, but steel string guitar players almost universally play with the strings arched at the bridge with no problems, and I've yet to hear first hand of anyone having problems playing mandolins with the strings arched at the bridge. Some (including me) feel like arched strings at the bridge make it easier to pick individual notes with the pick. If you arch the bridge enough, access to individual strings is so improved that they can be played with a bow (just look at a violin for confirmation).

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MISTAHCOUGHDROP

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## Ed Goist

John, you make a strong and compelling argument for the use of the cylindrical radiused fretboard.
I see from you site that you use a 7.25" cylindrical radius. How did you decide on that radius?
Do you feel it's kind of a _'sweet spot'_ where one gets maximum, improved ease of fretting and comfort, yet also has a saddle relatively flat enough for easy and even strumming? 
Is the 7.25" radius on the saddle at all noticeable while playing?
Thanks.

_(post edited after going to John's website and finding the radius he uses on his mandolins)_

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## amowry

Great, thoughtful post John (as usual)-- you much more eloquently stated what I was trying to get across in terms of leveling the frets creating a conical radius.

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## sunburst

Ed, I decided on the 7 1/4" radius by starting out by drawing arcs sort of like in post 14 above and realizing that a narrow 'board like a mandolin's seems pretty flat with a bigger radius. Also, I built a couple of banjo necks with radiused 'boards, the first one with a 16" radius (Martin guitar) and the second with a 12" radius (Gibson guitar). The 16" radius was hardly noticeable on the banjo neck, and the 12" was about right, I thought. A mandolin neck is narrower than a banjo neck, so I decided to try a tighter radius yet, and since I have a gauge for a 7 1/4" radius (Fender guitar) I tried it and it seemed to work well, so I've stuck with it.
As I said in an earlier post, it does not feel extreme, and some people don't even notice it. I've even had people play my mandolins and say something like; "have you ever tried an arched fingerboard?" or in one case, "pretty good, but I miss my radiused fingerboard".
So, when the 'board is as narrow as a mandolin 'board, the radius needs to be pretty small to be felt, but IMO playability is the important thing whether the arch is directly perceived or not. In other words, I don't care whether people notice the arch or not, I just want them to say to themselves; "this mandolin really plays well", and that seems to happen most with an arched 'board with a radius somewhere below 10" or so.

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## Dale Ludewig

I just finished up a rework on a mandolin originally built by me and went to a 7 1/4" radius (cylindrical).  It was requested by the owner.  At first I was a bit concerned, especially when I was feeling it without strings on.  But after strings were on, it's noticeably rounder than a 12" radius, but compared to a 9 1/2" which was on there before, nothing dramatic.  It plays very nicely.

One thing that one must realize is that with a cylindrical board that the outside edges get thinner as you go up the neck.  This is just due to the physics involved.  In fact I would guess, although I haven't actually drawn it out, that various conical layouts could be had of any starting radius and you could determine the radius at any other spot on the board by maintaining the same thickness on the outside edge.  Thus your action is same from the nut all the way to the end of the board.

Oh, and one more thought: I prefer to press my frets in with a caul before the fingerboard is glued on.  That would be very hard to do with a conical board.  You'd need a different caul for each fret.

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## amowry

Hey Dale, I press my frets too, and I was surprised to find that I can use a 12" aluminum caul for everything from about 9" up to 16" (which is the range of radii I use for my conical boards) with no problem. I think it's because mando boards are so narrow, and the caul has a very slight amount of give.

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## pawnee

i agree with williee in the fact that bluegrass can be played on a flat fretboard and sound great, the fretboard is narrow to begin with and do not notice the difference when i play both

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## Dale Ludewig

Andrew, as I think about it, I suppose I could do the same- use the same caul for a number of different radii.  My arbor press plunger, for lack of a better word, pivots in the middle and I already use that fact when I'm on the outside edge of the board.  Good idea.  I didn't mean to wander far afield from the OP.

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## jmagill

I'm considering getting a radiused fingerboard, and my luthier has suggested a cylindrical, rather than a conical shape, so these posts have been very useful. 

7 1/4" seems to be common for a tight radius, perhaps because gauges for that dimension are easily obtainable(?), but looking at the radii examples at Wikipedia's article here, a 6" radius looks like it would give me the noticeable arched feel I'm looking for. 

Has anyone here used a 6" radius with good results?

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