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Classical fretboard radius
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Author:  George Thomas [ Thu Jun 19, 2008 10:13 am ]
Post subject:  Classical fretboard radius
Hi All:

I attended the GAL conference last week and very much enjoyed the classical listening session. I did notice that several people mentioned that their guitars featured a radiussed fretboard. Do any of you classical builders have a typical FB radius that you use? Thanks.
Author:  Mike Collins [ Thu Jun 19, 2008 10:27 am ]
Post subject:  Re: Classical fretboard radius
I use one George.
Unless the client stipulates none-which has only happened once in 33 years!

I can't tell you the radius because i do it by eye.
It's very minimal and goes flat by the 12th fret.
Many players have told me they just love the feel mand the fact that barring is easier.

Welcome to the fold!!
Mike
Author:  douglas ingram [ Thu Jun 19, 2008 1:13 pm ]
Post subject:  Re: Classical fretboard radius
I've started using a radius fretboard on my classicals. I have left hand issues that are medical in nature, so I have to tweak my guitar to help. I made up some little plywood pieces cut to different radii, and set them against my index finger to see what fit best. I was most surprised when I found that the r=6" was the one! Its far tighter than is standard, but its not so extreme as its sounds because the amount of arc is very small, just the width of the nut.

The real challenge is flattening it out consistently along the length of the fingerboard and getting the saddle to the correct arc. Basic setup process.
Author:  patmguitars [ Thu Jun 19, 2008 2:38 pm ]
Post subject:  Re: Classical fretboard radius
Mike said:

Quote:
I can't tell you the radius because i do it by eye.
It's very minimal and goes flat by the 12th fret.


I am just about to experiment with radiused fingerboard. Basically, you either maintain a constant radius throughout or compound it negatively from nut to 19th fret. I am still debating which way to go.

I tried a guitar recently that had a constant radius (fairly flat, between 20 and 24 feet). It felt OK to me, but it didn't feel like that much of a difference. A client requested it on his guitar, so I will oblige.

My question to Mike is: Since there is a radius at the nut, then the nut is shaped accordingly. As you radius disappears at the 12th fret, does that mean that your saddle is made flat (notwithstanding any tappering of the fingerboard on the bass side)?

Cheers,

Pat
Author:  Mike Collins [ Thu Jun 19, 2008 5:29 pm ]
Post subject:  Re: Classical fretboard radius
Pat;
Nice question !
My saddle corresponds to the F.B. radius!
Even though there is NO radius fron the 12th fret to 19th!
You have to do this to keep (especially) the 4th string from buzzing!

This is a complicated system I;ve worked out for over 30 years!
I find it hard to put into words!
I've worked on many European guitars with a radiused saddle with NO
F.B. radius-WHY-because the 3rd & 4th string need more height above the frets because of their inherent nature to buzz !
It's a matter for me the maker to make sure the players of my guitars do NOT have a fretting issue -or string height issue that inhibits the player being able to use my guitars for their musical needs!

I hope this helps ya!
If not
Contact me be PM
Mike [:Y:]
Author:  douglas ingram [ Thu Jun 19, 2008 5:51 pm ]
Post subject:  Re: Classical fretboard radius
Pat,
However you decide to make the fingerboard, you need to consider the compound radius as a cone, and the saddle is the wide end. As a result of this, the radius at any point between the saddle and the nut is determined by this conical section.

I think that an easy way for you to work out your geometry would be to get a nice easily shaped piece of wood, perhaps pine or basswood, and cut it to length saddle to nut. Establish the radius that you want at each end, and then work the in between wood to the conical section. You can easily pick off the radius at any point along the length.

I, too, find a 24" radius to be pretty insignificant, may as well be flat. It may be enough for some. I'm loving my 6" radius fingerboard!

Mike,

That's a very interesting solution. I'd like to learn more about it if you're ever up to it.
Author:  patmguitars [ Thu Jun 19, 2008 7:44 pm ]
Post subject:  Re: Classical fretboard radius
Thanks Mike and Doug!

So, here is how I see it:

Given that:

-The nut contour follows the f.b. radius at its end. I will then adjust it so that the strings sit at their normal height above the first fret (I normally set it so that the space between the fret and string is about equal to the thickness of that particular string. There are probably better ways, but this one works for me [:Y:] )

-I want a string height of 3mm at the 12th fret for the 1st string, with a gradual increase so that the 6th string is at 4mm. Pretty standard so far, but on top of the radius, there is a gradual tappering of the fingerboard on the bass side to keep the string plan more even. My f.b. normally starts at 6.5mm at the nut end all across. The treble side remains at 6.5 throughout, the bass sides goes down by 1mm to 5.5 at the 19th fret.

This could pose a relatively simple equation IF the radius is constant or if it compounds gradually to the 19th fret. I does however becomes more complicated if the compounding goes from the 1st to the 12th fret: You now have two different plans on the f.b. (a radius part, from 1 to 12, and a flat part, from 12 to 19). Since the string are on a straight line, this creates a challenge: how do you maximise string height so that is maintains a steady progression from the 1st to the 19th fret. BTW, I haven't even mention neck relief yet. Where is this taking me??? wow7-eyes

So, in order to get it right the first time, I think I will go with a constant radius of probably 20 feet on the first go round. I will use you idea of a dummy wood saddle Doug, so that I don't waist 2 or 3 bone saddles before I get it right. You got to remember to take baby steps in lutherie. I have learned not to go radical to quickly... oops_sign

This situation can probably lead to some pretty deep thoughts! As Kelly (Al Bundy's "gifted" daughter on "Married With Children") once said: "The mind wobbles..." laughing6-hehe

Cheers guys,

Pat
Author:  George Thomas [ Thu Jun 19, 2008 10:56 pm ]
Post subject:  Re: Classical fretboard radius
Hi All:

Well there are some pretty interesting responses to the question but I think Mike's "doing it by eye" seems doable. The range of 6" radius to 20" is even more than the range of radius-sanding blocks from StewMac. Pat did you mean 20 inches? 20 feet would be pretty subtle on a F.B. I think maybe a few dummy F.B.s each with different radius will give me something with which to test the feel of the curve. Thanks.
Author:  Kent Chasson [ Fri Jun 20, 2008 1:01 am ]
Post subject:  Re: Classical fretboard radius
douglas ingram wrote:
Pat,
However you decide to make the fingerboard, you need to consider the compound radius as a cone, and the saddle is the wide end. As a result of this, the radius at any point between the saddle and the nut is determined by this conical section.


Douglas, for what it's worth, a compound radius board doesn't have to be conical. The whole thing gets real complicated real fast (probably why Mike can't put it into words). But if the goal is to start off with a the frets forming a straight line under the string path then all you have to do is determine the curve at the nut and the curve at the saddle and work back from there.

Fortunately, there's an article in a fairly recent GAL magazine with some nice graphics that illustrate it better than I can say it but it can be just about any curve you want, within reason.

George, if you want to try some different profiles, I've got a jig on an edge sander that makes quick work of it. All you'ld have to do is make some small templates/guides for the radii you want and plug them in. You're welcome to stop by and mess with it.
Author:  douglas ingram [ Fri Jun 20, 2008 9:27 am ]
Post subject:  Re: Classical fretboard radius
Kent Chasson wrote:

Douglas, for what it's worth, a compound radius board doesn't have to be conical. The whole thing gets real complicated real fast (probably why Mike can't put it into words).


True, but it helps to think of a cone as the basic geometry when first trying to conceive of what you're working with.
Author:  patmguitars [ Fri Jun 20, 2008 12:07 pm ]
Post subject:  Re: Classical fretboard radius
George said:

Quote:
Pat did you mean 20 inches?


Yes! 20 inches. Brain freeze. I seem to get those from time to time... idunno

Cheers

Pat
Author:  Mike Collins [ Fri Jun 20, 2008 12:13 pm ]
Post subject:  Re: Classical fretboard radius
Pat & Kent you've both have done a great job of explaining the idea!

Print out copies to distribute to makers!

Mike
[:Y:]
Author:  CWLiu [ Sat Jun 21, 2008 12:56 am ]
Post subject:  Re: Classical fretboard radius
I like mine to have a little radius, maybe less than 0.5 mm from edge to center. It seems a dead-flat fingerboard will become concave later due to the shrinkage. Besides, my fingerboards are usually kinda spiral lengthwise.
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